Logopedics Phoniatrics Vocology
ISSN: 1401-5439 (Print) 1651-2022 (Online) Journal homepage: http://www.tandfonline.com/loi/ilog20
Gender differences in risk factors of benign vocal fold disease in Korea: the fifth Korea National Health and Nutritional Examination Survey Haewon Byeon To cite this article: Haewon Byeon (2015): Gender differences in risk factors of benign vocal fold disease in Korea: the fifth Korea National Health and Nutritional Examination Survey, Logopedics Phoniatrics Vocology To link to this article: http://dx.doi.org/10.3109/14015439.2015.1004365
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ORIGINAL ARTICLE
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Gender differences in risk factors of benign vocal fold disease in Korea: the fifth Korea National Health and Nutritional Examination Survey
HAEWON BYEON1,2 1Department
of Speech Language Pathology & Audiology, Nambu University, Gwangju, Republic of Korea, and 2SpeechLanguage Pathology Center, Nambu University, Gwangju, Republic of Korea
Abstract The aim of this study was to confirm the prevalence rate of benign vocal fold disease (BVFD) based on gender in the Korean adult population and investigate potential risk factors of BVFD. Subjects were 8,677 non-institutionalized civilian adults over the age of 19 (3,788 males and 4,899 females) who completed the laryngeal examination of the fifth Korea National Health and Nutrition Examination Survey. Poisson regression analyses were conducted to examine the potential risk factors of BVFD. The prevalence rates of BVFD were similar in men (2.7%) and women (2.6%). When adjusted for covariates, men with self-reported voice problems had a 6.7 times greater risk (RR 6.72, 95% CI 4.17–10.84) of BVFD (P ⬍ 0.01). In addition, women with self-reported voice problems (RR 4.71, 95% CI 3.01–7.37) and current smokers (RR 1.97, 95% CI 1.01–3.81) were more likely to have BVFD (P ⬍ 0.01). There are gender differences in the risk factors of BVFD. In order to prevent BVFD, the enactment of guidelines reflecting gender differences is required. Key words: Benign vocal fold disease, dysphonia, gender difference, laryngeal disorders, risk factor
Introduction Since benign vocal fold diseases (BVFDs), such as vocal nodules and vocal polyps, have a high rate of recurrence even after successful operations and vocal treatments, it is vital to elucidate the risk factors and prevent them. Over the past 10 years, many researchers have been interested in the risk factors of dysphonia, and as a result age, gender, professional voice use, self-reported voice problems, alcohol consumption, smoking, and xerostomia have been reported as risk factors for dysphonia (1–5). Nevertheless, these studies have not paid attention to gender differences while exploring risk factors for laryngeal disorders. Gender differences in BVFD should be considered for the following reasons. First, the vocal cords of men and women are anatomically different. Voice is produced by the vibration of vocal cords, and women have approximately 15% less hyaluronic acid in the lamina propria of their vocal cords than do men (2). Thus,
women’s relative shortage of hyaluronic acid ultimately makes it more important for women than for men to protect their vocal cords from abuse of voice. Second, there is also a difference in the fundamental frequency, or number of vibrations per second, and since women have a higher fundamental frequency than men BVFD is more likely in women who abuse their voice for extended periods of time (6). Third, there are gender differences in health risk behaviors, such as smoking and drinking, which can directly affect BVFD. Gender is one of the major factors affecting health behaviors, and women generally engage in risky behaviors, such as smoking and drinking, less frequently (7). Fourth, in many studies, women complain of voice problems more than do men (8,9), and it is reported that they have a higher risk of laryngeal disorders (8–10). There may be gender differences in risk factors related to voice problems, and interventions should differ accordingly. Therefore, studies considering
Correspondence: Haewon Byeon, DrSc, Department of Speech Language Pathology & Audiology, Nambu University, CheomdanJungangro23, Gwangsan-gu, Gwangju, 506-706, Republic of Korea. Fax: ⫹ 82-62-972-6200. E-mail: [email protected] (Received 6 August 2014 ; accepted 29 December 2014 ) ISSN 1401-5439 print/ISSN 1651-2022 online © 2015 Informa UK, Ltd. DOI: 10.3109/14015439.2015.1004365
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H. Byeon
gender differences are required in order to determine the potential risk factors of BVFD and change modifiable risks such as smoking. Although there have been plenty of studies on risk factors of dysphonia, the majority of these studies have merely investigated demographic characteristics or health risk factors (8,10,11,12,14), and few studies have analyzed the risk factors of BVFD considering gender differences (13). This study 1) confirmed the prevalence rate of BVFD based on gender in an adult population and 2) investigated the potential risk factors of BVFD.
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Materials and methods Data source and participants Study subjects were adults 19 years and older who participated in the fifth Korea National Health and Nutrition Examination Survey (KNHANES V), a nationwide representative survey of the non-institutionalized population in the Republic of Korea, and who then participated in an otolaryngology examination (15). The KNHANES is a nationwide crosssectional survey conducted annually by The Korea Centers for Disease Control and Prevention. It employs a rolling sampling design that uses a complex, stratified multistage probability cluster survey of representative non-institutionalized civilians. The KNHANES sampling process is described in detail elsewhere (16). Briefly, the creators of the survey redesign the KNHANES from once every three years to once every year in order to provide timely health statistics for monitoring changes in health risk factors and diseases and developing associated public health policies and health programs. The fifth KNHANES, conducted in 2010–2012, was composed of three component surveys: a health interview, health examination, and nutrition survey. Trained medical staff and interviewers performed the health interview and health examination at a mobile examination center and at participants’ households. The KNHANES V was conducted on 31,596 persons out of 11,400 households with a participation rate of 80.8% (n ⫽ 25,533). The survey was approved by the Institutional Review Board (IRB) of the Korean Centers for Disease Control and Prevention (2011-02CON-06). This study targeted 10,134 persons who completed both the health survey and the laryngoscope examination. Of these, 1,457 persons whose laryngoscopic findings could not be determined were excluded from the research, and data from 8,677 persons (3,788 males, 4,889 females) were analyzed.
Measurement For the health interview, the survey on level of education and economic activity was conducted by
individual interviews, and the survey on behaviors regarding health, such as smoking and alcohol consumption, was executed with self-administered questionnaires. Benign vocal fold disease (BVFD) Participants who were 19 years of age or older had an endoscopic laryngeal examination. A total of 135 otolaryngologists from 43 general hospitals conducted endoscopic laryngeal examinations for laryngeal lesions using a 70° rigid endoscope that was attached to a CCD camera. Laryngoscopic findings of organic changes such as cord nodules and vocal polyps were recorded. Small, bilateral, symmetric, and sessile lesions in the mid-membranous vocal cord were diagnosed as vocal nodules, while relatively large, unilateral, or asymmetric, pedunculated lesions in the mid-membranous vocal cord were diagnosed as vocal polyps (16). The laryngeal examinations were collaborating with the Korean Society of Otorhinolaryngology–Head and Neck Surgery providing technical advice and highly trained otolaryngologists. Before the research, frequently occurring errors of the criteria were examined through theory education, pre-training, and mock surveys. The Epidemiologic Survey Committee of the Korean Otolaryngologic Society made a disease decision protocol. The index of coincidence evaluation was executed twice, and the quality improvement committee re-evaluated the pictures and videos (640 ⫻ 480-sized audio-video interleave files which were compressed by DivX 4.12 codec using a compression rate of 6 Mb/s) from the otolaryngologists’ examinations and computed the results. The laryngeal examination index of coincidence was 75%. In this study, the following were defined as BVFDs: vocal nodules, laryngeal polyps, intracordal cysts, Reinke’s edema, laryngeal granuloma, glottic sulcus, and laryngeal keratosis (17).
Potential risk factors The subjects were asked about their age, education level, occupation, income, smoking, drinking, and self-reported voice problems. Ages were classified into the following categories: 19–39, 40–59, and 60 ⫹ years. Education levels were classified into the following categories: less than elementary school, middle school, high school, and college or higher. Levels of income for households were classified into four quartiles. Occupations were surveyed based on the Korean Standard Classification of Occupations 6th Revision (18) and classified into the following categories: economically inactive (unemployed
Gender differences and benign vocal fold disease
subjects, 3,788 subjects (43.6%) were men and 4,988 (57.4%) were women. The average age was 50.6 years (SD 16.3) for men and 50.0 years (SD 16.8) for women. For level of education, most women were primary school graduates (31.4%) or high school graduates (31.4%), while most men were high school graduates (35.1%) or university graduates (31.4%). In terms of occupation, most men (38.7%) were non-manual workers, whereas most women (53.5%) were economically inactive. Men were more likely than women to be past/current smokers and to drink more than once a month. The prevalence rates of BVFD were similar in men (2.7%) and women (2.6%).
persons, homemakers, and students), non-manual (managers, clerical workers, and service and sales workers), and manual (skilled agricultural/forestry/ fishery workers, craft and related trades workers, elementary occupations). Smoking was classified into the following categories: current smokers, past smokers, and non-smokers. Alcohol drinking was dichotomized as less than once per month and over once per month. Those who currently reported having problems with their voice were classified as having self-reported voice problems.
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Statistical analysis Chi-square tests were used to compare the prevalence of BVFD by age, education level, occupation, income, smoking, alcohol drinking, and self-reported voice problem. Poisson regression analyses were used to examine the potential risk factors for BVFD. All analyses were performed using IBM SPSS version 20.0 (IBM, Inc., Chicago, IL, USA).
Comparison of characteristics of BVFD based on gender The characteristics of BVFD based on gender are presented in Table II. The results of a cross-test indicated that there was a significant difference in the self-reported voice problems of men and women. The prevalence rates of BVFD for people with selfreported voice problems were 10.9% for men and 9.5% for women, showing that the prevalence rates were five times higher, respectively, than for people without self-reported voice problems (P ⬍ 0.05).
Results General characteristics of subjects based on gender The general characteristics of subjects based on gender are presented in Table I. Out of the total 8,677
Table I. General characteristics of subjects based on gender. Variables
Age (weighted mean ⫾ SE) Education level ⱕ Elementary school Middle school High school ⱖ College Income (home) First quartile Second quartile Third quartile Fourth quartile Occupation Economically inactive population Non-manual Manual Smoking Non-smoker Past smoker Current smoker Alcohol drinking (ⱖ 1 per month) Yes Self-reported voice problems Yes Benign vocal fold disease Yes
3
Male
Female
Total
(n ⫽ 3,788)
(n ⫽ 4,899)
(n ⫽ 8,677)
50.0 ⫾ 16.8
50.3 ⫾ 16.6
50.6 ⫾ 16.3 597 433 1,199 1,189
(17.5) (12.7) (35.1) (31.4)
1,419 (31.4) 465 (10.3) 1,421 (31.4) 1217(26.9)
2,016 898 2,620 2,406
(25.4) (11.3) (33.0) (30.3)
680 972 1,047 1,032
(18.2) (26.1) (28.1) (27.7)
1,002 1,297 1,261 1,251
1,682 2,269 2,308 2,283
(19.7) (26.6) (27.0) (26.7)
(20.8) (27.0) (26.2) (26.0)
856 (25.2)
2,419 (53.5)
3,275 (41.4)
1,316 (38.7) 1,225 (36.1)
1,331 (29.4) 771 (17.1)
2,647 (33.4) 1,996 (25.2)
602 (17.6) 1,396 (40.8) 1,424 (41.6)
4,004 (88.6) 271 (6.0) 244 (5.4)
4,606 (58.0) 1,667 (21.0) 1,668 (21.0)
2,877 (84.5)
2,810 (62.6)
5,687 (72.0)
256 (6.8)
337 (6.9)
593 (6.8)
103 (2.7)
126 (2.6)
229 (2.6)
4
H. Byeon Table II. Comparison of characteristics of BVFD based on Gender, %. Variables
Male (n ⫽ 3,788)
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Normal Age 19–39 years 40–59 years 60 ⫹ years Education level Elementary school Middle school High school ⱖ College Income First quartile Second quartile Third quartile Fourth quartile Occupation Economically inactive population Non-manual Manual Smoking Non-smoker Past smoker Current smoker Alcohol drinking (ⱖ 1 per month) No Yes Self-reported voice problems No Yes
P
BVFD
Female (n ⫽ 4,889) Normal
BVFD
0.341 97.2 96.9 97.8
2.8 3.1 2.2
97.8 98.4 96.9 96.8
2.2 1.6 3.1 3.2
97.9 97.1 97.5 96.7
2.1 2.9 2.5 3.3
97.5 97.1 97.1
2.5 2.9 2.9
97.5 97.2 97.1
2.5 2.8 2.9
97.0 97.3
3.0 2.7
97.9 89.1
2.1 10.9
P
0.333 97.0 97.8 97.4
3.0 2.2 2.6
97.3 98.3 97.9 96.9
2.7 1.7 2.1 3.1
97.5 97.6 97.3 97.4
2.5 2.4 2.7 2.6
97.7 96.7 97.9
2.3 3.3 2.1
97.6 96.7 95.5
2.4 3.3 4.5
97.3 97.5
2.7 2.5
97.9 90.5
2.1 9.5
0.246
0.238
0.438
0.962
0.810
0.105
0.888
0.085
0.681
0.700
⬍ 0.001
⬍ 0.001
BVFD ⫽ benign vocal fold disease.
BVFD risk factors for men BVFD risk factors for men are illustrated in Table III. The result of an analysis of the crude model indicated that self-reported voice problems were a risk factor of BVFD for men. Men with self-reported voice problems had a 5.7 times greater risk (RR 5.66, 95% CI 3.59–8.92) of BVFD than those without (P ⬍ 0.01). Even in the model that adjusted for all confounding variables, men with self-reported voice problems had a 6.7 times greater risk (RR 6.72, 95% CI 4.17– 10.84) of BVFD than those without (P ⬍ 0.01). BVFD risk factors for women BVFD risk factors for women are presented in Table IV. The result of an analysis of the crude model indicated that current smoking and self-reported voice problems were risk factors of BVFD for women. Women who were currently smoking had a 1.9 times greater risk (RR 1.94, 95% CI 1.03–3.68) of BVFD than those who were not (P ⬍ 0.05). Even in the model that adjusted for all confounding variables, current smoking and self-reported
voice problems were significant risk factors of BVFD. Women who were currently smoking had a 2 times greater risk (RR 1.97, 95% CI 1.01–3.81) of BVFD than those who were not (P ⬍ 0.05). In addition, women with self-reported voice problems had a 4.7 times greater risk (RR 4.71, 95% CI 3.01–7.37) of BVFD than those without (P ⬍ 0.01).
Discussion This study analyzed risk factors of BVFD based on gender using otorhinolaryngological examination data from a national survey. In this study, the prevalence rate of BVFD for the overall local community population of 8,677 subjects was 2.6%, with 2.7% for men and 2.6% for women, exhibiting virtually no difference between genders. Contrary to this study, many studies that have analyzed differences of voice problems between men and women have reported that there are gender differences in the prevalence rate of dysphonia (13,14). In studies on teachers, although there were no differences in career years or workloads between genders, women not only
Gender differences and benign vocal fold disease
5
Table III. Risk ratio and 95% confidence interval by Poisson regression model for benign vocal fold disease in men.
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Variable (Reference group) Age (19–39 years) 40–59 years 60 ⫹ years Education level (Elementary school) Middle school High school ⱖ College Income (First quartile) Second quartile Third quartile Fourth quartile Occupation (Economically inactive) Non-manual Manual Smoking (Non-smoker) Past smoker Current smoker Alcohol drinking (⬍ 1 per month) ⱖ 1 per month Self-reported voice problems Yes
Crude RR (95% CI)
Adjusted RR (95% CI)
1.09 (0.68–1.73) 0.76 (0.45–1.28)
1.12 (0.66–1.90) 0.75 (0.37–1.52)
0.74 (0.29–1.87) 1.43 (0.75–2.71) 1.48 (0.78–2.81)
0.65 (0.25–1.69) 1.23 (0.59–2.59) 1.45 (0.64–3.29)
1.41 (0.74–2.70) 1.21 (0.63–2.34) 1.62 (0.86–3.04)
1.20 (0.56–2.57) 1.09 (0.49–2.39) 1.42 (0.64–3.13)
1.18 (0.69–2.03) 1.17 (0.68–2.02)
0.88 (0.45–1.72) 1.18 (0.63–2.20)
1.13 (0.62–2.06) 1.16 (0.64–2.11)
1.25 (0.66–2.39) 1.24 (0.66–2.36)
0.89 (0.52–1.54)
0.69 (0.38–1.25)
5.66 (3.59–8.92)**
6.72 (4.17–10.84)**
*P ⬍ 0.05; **P ⬍ 0.01.
experienced significantly more voice problems (14) and had a 1.4–3.6 times higher risk of voice problems than men (8,14), but they also had around a 1.8 times higher risk of absence from work due to their voice problems (10).
Differences between genders have also been reported in visitation rates to medical institutions. According to the National Ambulatory Medical Care Survey from 2005 through 2007, among those who visited medical institutions, men constituted 31.9%,
Table IV. Risk ratio and 95% confidence interval by Poisson regression model for benign vocal fold disease in women. Variable (Reference group) Age (19–39 years) 40–59 years 60 ⫹ years Education level (Elementary school) Middle school High school ⱖ College Income (First quartile) Second quartile Third quartile Fourth quartile Occupation (Economically inactive) Non-manual Manual Smoking (Non-smoker) Past smoker Current smoker Alcohol drinking (⬍ 1 per month) ⱖ 1 per month Self-reported voice problems Yes *P ⬍ 0.05; **P ⬍ 0.01.
Crude RR (95% CI)
Adjusted RR (95% CI)
0.72 (0.47–1.11) 0.87 (0.57–1.34)
0.79 (0.47–1.35) 0.87 (0.41–1.85)
0.62 (0.29–1.34) 0.76 (0.47–1.24) 1.14 (0.73–1.79)
0.60 (0.26–1.38) 0.71 (0.36–1.39) 0.98 (0.46–2.07)
0.96 (0.56–1.63) 1.08 (0.64–1.83) 1.06 (0.63–1.79)
0.94 (0.52–1.72) 0.92 (0.48–1.73) 0.87 (0.45–1.70)
1.47 (0.98–2.19) 0.91 (0.52–1.60)
1.54 (0.98–2.42) 1.01 (0.56–1.82)
1.41 (0.71–2.83) 1.94 (1.03–3.68)*
1.36 (0.67–2.78) 1.97 (1.01–3.81)*
0.93 (0.64–1.36)
0.80 (0.52–1.22)
4.97 (3.28–7.55)**
4.71 (3.01–7.37)**
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H. Byeon
while women constituted 68.1%, showing that the proportion of women is about twice that of men (19). Although it has been reported in these preceding studies that women are more vulnerable to dysphonia, the scientific mechanism for this phenomenon has not yet been clarified. On the contrary, there was no gender difference in the prevalence rate of BVFD in this study conducted on the local community population. There are two possible reasons for this result. First, the majority of preceding studies were performed on teachers (8,10,13,14) or on people who had visited medical institutions (19). Given that there are people who do not visit medical institutions even when they recognize their voice problems, there is a possibility that the prevalence rate of laryngeal disorders for the actual population may differ from those recorded in the data of medical institutions. Second, women are more likely a group that tends to take precautionary actions against diseases than a group susceptible to laryngeal disorders. Women are likely to evaluate their health status more negatively than men (20), they are more precautionary (21), and they are more likely to visit medical institutions for their voice problems (19,22). Thus, although women visited medical institutions more frequently than men, in actuality, it is judged that there is no gender difference in the prevalence rate of BVFD for the general population. In this study, there were gender differences in risk factors related to BVFD. The BVFD risk factor for men was self-reported voice problems, and, for women, smoking and self-reported voice problems were predictive factors. Self-reported voice problems had a significant association for both men and women. In preceding studies that investigated risk factors of dysphonia, self-reported voice problems were a major predictive factor for dysphonia even after the adjustment of gender (1,23). Moreover, the risk of dysphonia was 5.2 times higher in the group that recognized their own voice problems (13). This consistent trend in preceding studies supports the result of this study that subjective recognition of voice problems is a significant predictive factor of BVFD for both men and women. Meanwhile, smoking was a risk factor of BVFD only for women. In many studies, smoking has been reported to be a risk factor for laryngeal disorders. Smoking is not just the major cause of Reinke’s edema (24,25), but it also has a significant relationship with chronic laryngitis, laryngeal keratosis, and laryngeal leukoplakia (26,27). Moreover, in an epidemiological study on senior citizens, those who were currently smoking had a 2.2 times greater risk of laryngeal lesions than those who were not (1). The result of the analysis on risk factors of BVFD based
on gender indicated that only women smokers had twice the risk of BVFD, which is likely the result of the difference in the smoking rate between men and women. In this study, the proportion of men who were currently smoking (41.6%) was around 8 times higher than that of women (5.4%), and the proportion of past smokers for men (40.8%) was about 7 times higher than that for women (6.0%). On the other hand, the proportion of non-smoking women (88.6%) was about 5 times higher than that for men (17.6%). The BVFD prevalence rate also showed gender differences; women smokers had double the prevalence rate of BVFD than non-smoking women, whereas the prevalence rates for non-smoking and smoking men did not differ. Since gender is a major factor affecting health risk behaviors (9), analyses that take gender into consideration are required in future studies on health risk behaviors related to BVFD. The limitations of this study are as follows. First, there may be potential confounding factors related to BVFD other than those included in this study. Second, because this study was cross-sectional in nature, the results cannot be translated as indicating a causal relationship. Third, in this epidemiological study, medical history of thyroid disease and arthritis which can affect dysphonia was not surveyed, which is required in the future studies.
Conclusion In this cross-sectional study, gender differences in BVFD risk factors were found. The BVFD risk factor for men was self-reported voice problems, while for women the risk factors were smoking and self-reported voice problems. In order to prevent BVFD, the enactment of guidelines reflecting gender differences is required. Furthermore, in order to explore the causal relationship among identified risk factors, longitudinal studies are also required.
Acknowledgements The author wishes to thank the Korea Centers for Disease Control and Prevention for providing the raw data for analysis. Declaration of interest: The authors declare that they have no competing interest. References 1. Byeon H, Lee Y. Laryngeal pathologies in older Korean adults and their association with smoking and alcohol consumption. Laryngoscope. 2013;123:429–33.
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ISSN: 1401-5439 (Print) 1651-2022 (Online) Journal homepage: http://www.tandfonline.com/loi/ilog20
Gender differences in risk factors of benign vocal fold disease in Korea: the fifth Korea National Health and Nutritional Examination Survey Haewon Byeon To cite this article: Haewon Byeon (2015): Gender differences in risk factors of benign vocal fold disease in Korea: the fifth Korea National Health and Nutritional Examination Survey, Logopedics Phoniatrics Vocology To link to this article: http://dx.doi.org/10.3109/14015439.2015.1004365
Published online: 20 Feb 2015.
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Date: 11 November 2015, At: 14:28
Logopedics Phoniatrics Vocology, 2015; Early Online: 1–7
ORIGINAL ARTICLE
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Gender differences in risk factors of benign vocal fold disease in Korea: the fifth Korea National Health and Nutritional Examination Survey
HAEWON BYEON1,2 1Department
of Speech Language Pathology & Audiology, Nambu University, Gwangju, Republic of Korea, and 2SpeechLanguage Pathology Center, Nambu University, Gwangju, Republic of Korea
Abstract The aim of this study was to confirm the prevalence rate of benign vocal fold disease (BVFD) based on gender in the Korean adult population and investigate potential risk factors of BVFD. Subjects were 8,677 non-institutionalized civilian adults over the age of 19 (3,788 males and 4,899 females) who completed the laryngeal examination of the fifth Korea National Health and Nutrition Examination Survey. Poisson regression analyses were conducted to examine the potential risk factors of BVFD. The prevalence rates of BVFD were similar in men (2.7%) and women (2.6%). When adjusted for covariates, men with self-reported voice problems had a 6.7 times greater risk (RR 6.72, 95% CI 4.17–10.84) of BVFD (P ⬍ 0.01). In addition, women with self-reported voice problems (RR 4.71, 95% CI 3.01–7.37) and current smokers (RR 1.97, 95% CI 1.01–3.81) were more likely to have BVFD (P ⬍ 0.01). There are gender differences in the risk factors of BVFD. In order to prevent BVFD, the enactment of guidelines reflecting gender differences is required. Key words: Benign vocal fold disease, dysphonia, gender difference, laryngeal disorders, risk factor
Introduction Since benign vocal fold diseases (BVFDs), such as vocal nodules and vocal polyps, have a high rate of recurrence even after successful operations and vocal treatments, it is vital to elucidate the risk factors and prevent them. Over the past 10 years, many researchers have been interested in the risk factors of dysphonia, and as a result age, gender, professional voice use, self-reported voice problems, alcohol consumption, smoking, and xerostomia have been reported as risk factors for dysphonia (1–5). Nevertheless, these studies have not paid attention to gender differences while exploring risk factors for laryngeal disorders. Gender differences in BVFD should be considered for the following reasons. First, the vocal cords of men and women are anatomically different. Voice is produced by the vibration of vocal cords, and women have approximately 15% less hyaluronic acid in the lamina propria of their vocal cords than do men (2). Thus,
women’s relative shortage of hyaluronic acid ultimately makes it more important for women than for men to protect their vocal cords from abuse of voice. Second, there is also a difference in the fundamental frequency, or number of vibrations per second, and since women have a higher fundamental frequency than men BVFD is more likely in women who abuse their voice for extended periods of time (6). Third, there are gender differences in health risk behaviors, such as smoking and drinking, which can directly affect BVFD. Gender is one of the major factors affecting health behaviors, and women generally engage in risky behaviors, such as smoking and drinking, less frequently (7). Fourth, in many studies, women complain of voice problems more than do men (8,9), and it is reported that they have a higher risk of laryngeal disorders (8–10). There may be gender differences in risk factors related to voice problems, and interventions should differ accordingly. Therefore, studies considering
Correspondence: Haewon Byeon, DrSc, Department of Speech Language Pathology & Audiology, Nambu University, CheomdanJungangro23, Gwangsan-gu, Gwangju, 506-706, Republic of Korea. Fax: ⫹ 82-62-972-6200. E-mail: [email protected] (Received 6 August 2014 ; accepted 29 December 2014 ) ISSN 1401-5439 print/ISSN 1651-2022 online © 2015 Informa UK, Ltd. DOI: 10.3109/14015439.2015.1004365
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gender differences are required in order to determine the potential risk factors of BVFD and change modifiable risks such as smoking. Although there have been plenty of studies on risk factors of dysphonia, the majority of these studies have merely investigated demographic characteristics or health risk factors (8,10,11,12,14), and few studies have analyzed the risk factors of BVFD considering gender differences (13). This study 1) confirmed the prevalence rate of BVFD based on gender in an adult population and 2) investigated the potential risk factors of BVFD.
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Materials and methods Data source and participants Study subjects were adults 19 years and older who participated in the fifth Korea National Health and Nutrition Examination Survey (KNHANES V), a nationwide representative survey of the non-institutionalized population in the Republic of Korea, and who then participated in an otolaryngology examination (15). The KNHANES is a nationwide crosssectional survey conducted annually by The Korea Centers for Disease Control and Prevention. It employs a rolling sampling design that uses a complex, stratified multistage probability cluster survey of representative non-institutionalized civilians. The KNHANES sampling process is described in detail elsewhere (16). Briefly, the creators of the survey redesign the KNHANES from once every three years to once every year in order to provide timely health statistics for monitoring changes in health risk factors and diseases and developing associated public health policies and health programs. The fifth KNHANES, conducted in 2010–2012, was composed of three component surveys: a health interview, health examination, and nutrition survey. Trained medical staff and interviewers performed the health interview and health examination at a mobile examination center and at participants’ households. The KNHANES V was conducted on 31,596 persons out of 11,400 households with a participation rate of 80.8% (n ⫽ 25,533). The survey was approved by the Institutional Review Board (IRB) of the Korean Centers for Disease Control and Prevention (2011-02CON-06). This study targeted 10,134 persons who completed both the health survey and the laryngoscope examination. Of these, 1,457 persons whose laryngoscopic findings could not be determined were excluded from the research, and data from 8,677 persons (3,788 males, 4,889 females) were analyzed.
Measurement For the health interview, the survey on level of education and economic activity was conducted by
individual interviews, and the survey on behaviors regarding health, such as smoking and alcohol consumption, was executed with self-administered questionnaires. Benign vocal fold disease (BVFD) Participants who were 19 years of age or older had an endoscopic laryngeal examination. A total of 135 otolaryngologists from 43 general hospitals conducted endoscopic laryngeal examinations for laryngeal lesions using a 70° rigid endoscope that was attached to a CCD camera. Laryngoscopic findings of organic changes such as cord nodules and vocal polyps were recorded. Small, bilateral, symmetric, and sessile lesions in the mid-membranous vocal cord were diagnosed as vocal nodules, while relatively large, unilateral, or asymmetric, pedunculated lesions in the mid-membranous vocal cord were diagnosed as vocal polyps (16). The laryngeal examinations were collaborating with the Korean Society of Otorhinolaryngology–Head and Neck Surgery providing technical advice and highly trained otolaryngologists. Before the research, frequently occurring errors of the criteria were examined through theory education, pre-training, and mock surveys. The Epidemiologic Survey Committee of the Korean Otolaryngologic Society made a disease decision protocol. The index of coincidence evaluation was executed twice, and the quality improvement committee re-evaluated the pictures and videos (640 ⫻ 480-sized audio-video interleave files which were compressed by DivX 4.12 codec using a compression rate of 6 Mb/s) from the otolaryngologists’ examinations and computed the results. The laryngeal examination index of coincidence was 75%. In this study, the following were defined as BVFDs: vocal nodules, laryngeal polyps, intracordal cysts, Reinke’s edema, laryngeal granuloma, glottic sulcus, and laryngeal keratosis (17).
Potential risk factors The subjects were asked about their age, education level, occupation, income, smoking, drinking, and self-reported voice problems. Ages were classified into the following categories: 19–39, 40–59, and 60 ⫹ years. Education levels were classified into the following categories: less than elementary school, middle school, high school, and college or higher. Levels of income for households were classified into four quartiles. Occupations were surveyed based on the Korean Standard Classification of Occupations 6th Revision (18) and classified into the following categories: economically inactive (unemployed
Gender differences and benign vocal fold disease
subjects, 3,788 subjects (43.6%) were men and 4,988 (57.4%) were women. The average age was 50.6 years (SD 16.3) for men and 50.0 years (SD 16.8) for women. For level of education, most women were primary school graduates (31.4%) or high school graduates (31.4%), while most men were high school graduates (35.1%) or university graduates (31.4%). In terms of occupation, most men (38.7%) were non-manual workers, whereas most women (53.5%) were economically inactive. Men were more likely than women to be past/current smokers and to drink more than once a month. The prevalence rates of BVFD were similar in men (2.7%) and women (2.6%).
persons, homemakers, and students), non-manual (managers, clerical workers, and service and sales workers), and manual (skilled agricultural/forestry/ fishery workers, craft and related trades workers, elementary occupations). Smoking was classified into the following categories: current smokers, past smokers, and non-smokers. Alcohol drinking was dichotomized as less than once per month and over once per month. Those who currently reported having problems with their voice were classified as having self-reported voice problems.
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Statistical analysis Chi-square tests were used to compare the prevalence of BVFD by age, education level, occupation, income, smoking, alcohol drinking, and self-reported voice problem. Poisson regression analyses were used to examine the potential risk factors for BVFD. All analyses were performed using IBM SPSS version 20.0 (IBM, Inc., Chicago, IL, USA).
Comparison of characteristics of BVFD based on gender The characteristics of BVFD based on gender are presented in Table II. The results of a cross-test indicated that there was a significant difference in the self-reported voice problems of men and women. The prevalence rates of BVFD for people with selfreported voice problems were 10.9% for men and 9.5% for women, showing that the prevalence rates were five times higher, respectively, than for people without self-reported voice problems (P ⬍ 0.05).
Results General characteristics of subjects based on gender The general characteristics of subjects based on gender are presented in Table I. Out of the total 8,677
Table I. General characteristics of subjects based on gender. Variables
Age (weighted mean ⫾ SE) Education level ⱕ Elementary school Middle school High school ⱖ College Income (home) First quartile Second quartile Third quartile Fourth quartile Occupation Economically inactive population Non-manual Manual Smoking Non-smoker Past smoker Current smoker Alcohol drinking (ⱖ 1 per month) Yes Self-reported voice problems Yes Benign vocal fold disease Yes
3
Male
Female
Total
(n ⫽ 3,788)
(n ⫽ 4,899)
(n ⫽ 8,677)
50.0 ⫾ 16.8
50.3 ⫾ 16.6
50.6 ⫾ 16.3 597 433 1,199 1,189
(17.5) (12.7) (35.1) (31.4)
1,419 (31.4) 465 (10.3) 1,421 (31.4) 1217(26.9)
2,016 898 2,620 2,406
(25.4) (11.3) (33.0) (30.3)
680 972 1,047 1,032
(18.2) (26.1) (28.1) (27.7)
1,002 1,297 1,261 1,251
1,682 2,269 2,308 2,283
(19.7) (26.6) (27.0) (26.7)
(20.8) (27.0) (26.2) (26.0)
856 (25.2)
2,419 (53.5)
3,275 (41.4)
1,316 (38.7) 1,225 (36.1)
1,331 (29.4) 771 (17.1)
2,647 (33.4) 1,996 (25.2)
602 (17.6) 1,396 (40.8) 1,424 (41.6)
4,004 (88.6) 271 (6.0) 244 (5.4)
4,606 (58.0) 1,667 (21.0) 1,668 (21.0)
2,877 (84.5)
2,810 (62.6)
5,687 (72.0)
256 (6.8)
337 (6.9)
593 (6.8)
103 (2.7)
126 (2.6)
229 (2.6)
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H. Byeon Table II. Comparison of characteristics of BVFD based on Gender, %. Variables
Male (n ⫽ 3,788)
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Normal Age 19–39 years 40–59 years 60 ⫹ years Education level Elementary school Middle school High school ⱖ College Income First quartile Second quartile Third quartile Fourth quartile Occupation Economically inactive population Non-manual Manual Smoking Non-smoker Past smoker Current smoker Alcohol drinking (ⱖ 1 per month) No Yes Self-reported voice problems No Yes
P
BVFD
Female (n ⫽ 4,889) Normal
BVFD
0.341 97.2 96.9 97.8
2.8 3.1 2.2
97.8 98.4 96.9 96.8
2.2 1.6 3.1 3.2
97.9 97.1 97.5 96.7
2.1 2.9 2.5 3.3
97.5 97.1 97.1
2.5 2.9 2.9
97.5 97.2 97.1
2.5 2.8 2.9
97.0 97.3
3.0 2.7
97.9 89.1
2.1 10.9
P
0.333 97.0 97.8 97.4
3.0 2.2 2.6
97.3 98.3 97.9 96.9
2.7 1.7 2.1 3.1
97.5 97.6 97.3 97.4
2.5 2.4 2.7 2.6
97.7 96.7 97.9
2.3 3.3 2.1
97.6 96.7 95.5
2.4 3.3 4.5
97.3 97.5
2.7 2.5
97.9 90.5
2.1 9.5
0.246
0.238
0.438
0.962
0.810
0.105
0.888
0.085
0.681
0.700
⬍ 0.001
⬍ 0.001
BVFD ⫽ benign vocal fold disease.
BVFD risk factors for men BVFD risk factors for men are illustrated in Table III. The result of an analysis of the crude model indicated that self-reported voice problems were a risk factor of BVFD for men. Men with self-reported voice problems had a 5.7 times greater risk (RR 5.66, 95% CI 3.59–8.92) of BVFD than those without (P ⬍ 0.01). Even in the model that adjusted for all confounding variables, men with self-reported voice problems had a 6.7 times greater risk (RR 6.72, 95% CI 4.17– 10.84) of BVFD than those without (P ⬍ 0.01). BVFD risk factors for women BVFD risk factors for women are presented in Table IV. The result of an analysis of the crude model indicated that current smoking and self-reported voice problems were risk factors of BVFD for women. Women who were currently smoking had a 1.9 times greater risk (RR 1.94, 95% CI 1.03–3.68) of BVFD than those who were not (P ⬍ 0.05). Even in the model that adjusted for all confounding variables, current smoking and self-reported
voice problems were significant risk factors of BVFD. Women who were currently smoking had a 2 times greater risk (RR 1.97, 95% CI 1.01–3.81) of BVFD than those who were not (P ⬍ 0.05). In addition, women with self-reported voice problems had a 4.7 times greater risk (RR 4.71, 95% CI 3.01–7.37) of BVFD than those without (P ⬍ 0.01).
Discussion This study analyzed risk factors of BVFD based on gender using otorhinolaryngological examination data from a national survey. In this study, the prevalence rate of BVFD for the overall local community population of 8,677 subjects was 2.6%, with 2.7% for men and 2.6% for women, exhibiting virtually no difference between genders. Contrary to this study, many studies that have analyzed differences of voice problems between men and women have reported that there are gender differences in the prevalence rate of dysphonia (13,14). In studies on teachers, although there were no differences in career years or workloads between genders, women not only
Gender differences and benign vocal fold disease
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Table III. Risk ratio and 95% confidence interval by Poisson regression model for benign vocal fold disease in men.
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Variable (Reference group) Age (19–39 years) 40–59 years 60 ⫹ years Education level (Elementary school) Middle school High school ⱖ College Income (First quartile) Second quartile Third quartile Fourth quartile Occupation (Economically inactive) Non-manual Manual Smoking (Non-smoker) Past smoker Current smoker Alcohol drinking (⬍ 1 per month) ⱖ 1 per month Self-reported voice problems Yes
Crude RR (95% CI)
Adjusted RR (95% CI)
1.09 (0.68–1.73) 0.76 (0.45–1.28)
1.12 (0.66–1.90) 0.75 (0.37–1.52)
0.74 (0.29–1.87) 1.43 (0.75–2.71) 1.48 (0.78–2.81)
0.65 (0.25–1.69) 1.23 (0.59–2.59) 1.45 (0.64–3.29)
1.41 (0.74–2.70) 1.21 (0.63–2.34) 1.62 (0.86–3.04)
1.20 (0.56–2.57) 1.09 (0.49–2.39) 1.42 (0.64–3.13)
1.18 (0.69–2.03) 1.17 (0.68–2.02)
0.88 (0.45–1.72) 1.18 (0.63–2.20)
1.13 (0.62–2.06) 1.16 (0.64–2.11)
1.25 (0.66–2.39) 1.24 (0.66–2.36)
0.89 (0.52–1.54)
0.69 (0.38–1.25)
5.66 (3.59–8.92)**
6.72 (4.17–10.84)**
*P ⬍ 0.05; **P ⬍ 0.01.
experienced significantly more voice problems (14) and had a 1.4–3.6 times higher risk of voice problems than men (8,14), but they also had around a 1.8 times higher risk of absence from work due to their voice problems (10).
Differences between genders have also been reported in visitation rates to medical institutions. According to the National Ambulatory Medical Care Survey from 2005 through 2007, among those who visited medical institutions, men constituted 31.9%,
Table IV. Risk ratio and 95% confidence interval by Poisson regression model for benign vocal fold disease in women. Variable (Reference group) Age (19–39 years) 40–59 years 60 ⫹ years Education level (Elementary school) Middle school High school ⱖ College Income (First quartile) Second quartile Third quartile Fourth quartile Occupation (Economically inactive) Non-manual Manual Smoking (Non-smoker) Past smoker Current smoker Alcohol drinking (⬍ 1 per month) ⱖ 1 per month Self-reported voice problems Yes *P ⬍ 0.05; **P ⬍ 0.01.
Crude RR (95% CI)
Adjusted RR (95% CI)
0.72 (0.47–1.11) 0.87 (0.57–1.34)
0.79 (0.47–1.35) 0.87 (0.41–1.85)
0.62 (0.29–1.34) 0.76 (0.47–1.24) 1.14 (0.73–1.79)
0.60 (0.26–1.38) 0.71 (0.36–1.39) 0.98 (0.46–2.07)
0.96 (0.56–1.63) 1.08 (0.64–1.83) 1.06 (0.63–1.79)
0.94 (0.52–1.72) 0.92 (0.48–1.73) 0.87 (0.45–1.70)
1.47 (0.98–2.19) 0.91 (0.52–1.60)
1.54 (0.98–2.42) 1.01 (0.56–1.82)
1.41 (0.71–2.83) 1.94 (1.03–3.68)*
1.36 (0.67–2.78) 1.97 (1.01–3.81)*
0.93 (0.64–1.36)
0.80 (0.52–1.22)
4.97 (3.28–7.55)**
4.71 (3.01–7.37)**
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H. Byeon
while women constituted 68.1%, showing that the proportion of women is about twice that of men (19). Although it has been reported in these preceding studies that women are more vulnerable to dysphonia, the scientific mechanism for this phenomenon has not yet been clarified. On the contrary, there was no gender difference in the prevalence rate of BVFD in this study conducted on the local community population. There are two possible reasons for this result. First, the majority of preceding studies were performed on teachers (8,10,13,14) or on people who had visited medical institutions (19). Given that there are people who do not visit medical institutions even when they recognize their voice problems, there is a possibility that the prevalence rate of laryngeal disorders for the actual population may differ from those recorded in the data of medical institutions. Second, women are more likely a group that tends to take precautionary actions against diseases than a group susceptible to laryngeal disorders. Women are likely to evaluate their health status more negatively than men (20), they are more precautionary (21), and they are more likely to visit medical institutions for their voice problems (19,22). Thus, although women visited medical institutions more frequently than men, in actuality, it is judged that there is no gender difference in the prevalence rate of BVFD for the general population. In this study, there were gender differences in risk factors related to BVFD. The BVFD risk factor for men was self-reported voice problems, and, for women, smoking and self-reported voice problems were predictive factors. Self-reported voice problems had a significant association for both men and women. In preceding studies that investigated risk factors of dysphonia, self-reported voice problems were a major predictive factor for dysphonia even after the adjustment of gender (1,23). Moreover, the risk of dysphonia was 5.2 times higher in the group that recognized their own voice problems (13). This consistent trend in preceding studies supports the result of this study that subjective recognition of voice problems is a significant predictive factor of BVFD for both men and women. Meanwhile, smoking was a risk factor of BVFD only for women. In many studies, smoking has been reported to be a risk factor for laryngeal disorders. Smoking is not just the major cause of Reinke’s edema (24,25), but it also has a significant relationship with chronic laryngitis, laryngeal keratosis, and laryngeal leukoplakia (26,27). Moreover, in an epidemiological study on senior citizens, those who were currently smoking had a 2.2 times greater risk of laryngeal lesions than those who were not (1). The result of the analysis on risk factors of BVFD based
on gender indicated that only women smokers had twice the risk of BVFD, which is likely the result of the difference in the smoking rate between men and women. In this study, the proportion of men who were currently smoking (41.6%) was around 8 times higher than that of women (5.4%), and the proportion of past smokers for men (40.8%) was about 7 times higher than that for women (6.0%). On the other hand, the proportion of non-smoking women (88.6%) was about 5 times higher than that for men (17.6%). The BVFD prevalence rate also showed gender differences; women smokers had double the prevalence rate of BVFD than non-smoking women, whereas the prevalence rates for non-smoking and smoking men did not differ. Since gender is a major factor affecting health risk behaviors (9), analyses that take gender into consideration are required in future studies on health risk behaviors related to BVFD. The limitations of this study are as follows. First, there may be potential confounding factors related to BVFD other than those included in this study. Second, because this study was cross-sectional in nature, the results cannot be translated as indicating a causal relationship. Third, in this epidemiological study, medical history of thyroid disease and arthritis which can affect dysphonia was not surveyed, which is required in the future studies.
Conclusion In this cross-sectional study, gender differences in BVFD risk factors were found. The BVFD risk factor for men was self-reported voice problems, while for women the risk factors were smoking and self-reported voice problems. In order to prevent BVFD, the enactment of guidelines reflecting gender differences is required. Furthermore, in order to explore the causal relationship among identified risk factors, longitudinal studies are also required.
Acknowledgements The author wishes to thank the Korea Centers for Disease Control and Prevention for providing the raw data for analysis. Declaration of interest: The authors declare that they have no competing interest. References 1. Byeon H, Lee Y. Laryngeal pathologies in older Korean adults and their association with smoking and alcohol consumption. Laryngoscope. 2013;123:429–33.
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