Women & Health, 55:419–431, 2015 Copyright © Taylor & Francis Group, LLC ISSN: 0363-0242 print/1541-0331 online DOI: 10.1080/03630242.2015.1022686
Physical Activity in Adolescence and Abdominal Obesity in Adulthood: A Case-Control Study Among Women Shift Workers ANDERSON DA SILVA GARCEZ, MS Post-Graduate Program in Collective Health, University of Vale do Rio dos Sinos, São Leopoldo, Brazil
MARIA TERESA ANSELMO OLINTO, PhD Post-Graduate Program in Collective Health, University of Vale do Rio dos Sinos, São Leopoldo; and Department of Nutrition, Federal University of Health Science of Porto Alegre, Porto Alegre, Brazil
RAQUEL CANUTO, PhD Department of Social Medicine, Federal University of Rio Grande do Sul State, Porto Alegre, Brazil
BEATRIZ ANSELMO OLINTO, PhD Post-Graduate Program in History, Unicentro, Paraná, Brazil
MARCOS PASCOAL PATTUSSI, PhD and VERA MARIA VIEIRA PANIZ, PhD Post-Graduate Program in Collective Health, University of Vale do Rio dos Sinos, São Leopoldo, Brazil
Physical activity may have a protective effect against abdominal obesity, an important risk factor for cardiometabolic diseases. Thus, the aim of this study was to examine the association between the practice of physical activities in adolescence and abdominal obesity in adulthood among women shift workers in Southern Brazil in 2011. This case-control study included 215 cases (waist circumference greater than or equal to 88 cm) and 326 controls. For both the case and control groups, participation in leisure-time physical Received November 21, 2013; revised June 4, 2014; accepted June 21, 2014. Address correspondence to Vera Maria Vieira Paniz, PhD, Post-Graduate Program in Collective Health, University of Vale do Rio dos Sinos, Av. Unisinos 950, C.P. 275, São Leopoldo, RS 93022-000, Brazil. E-mail: [email protected] 419
420
A. da Silva Garcez et al.
activities was most frequent in adolescence and was significantly less in adulthood. After adjusting for potential confounding factors, women who participated in five or more physical activities in adolescence were 50 percent less likely to have abdominal obesity than women who participated in one activity or no physical activities (Odds Ratio = 0.50; 95% confidential interval: 0.27–0.93, p value = .029). Participation in various types of leisure-time physical activities in adolescence may protect against abdominal obesity in adulthood, even if the number of physical activities decreases over time. This finding demonstrated the importance of physical activity as well as the period of life in which these should be encouraged for the prevention of health disorders, such as abdominal obesity. KEYWORDS abdominal circumference, women
obesity,
physical
activity,
waist
INTRODUCTION Abdominal obesity is considered one of the most harmful types of obesity because it is an independent risk factor for cardiometabolic diseases (Cameron et al. 2008; Klein et al. 2007). As a result, abdominal obesity has been directly linked to increased overall mortality independent of overall obesity (Jacobs et al. 2010; Pischon et al. 2008). The prevalence of abdominal obesity has increased in recent decades (Visscher and Seidell 2004; Walls et al. 2011), and this condition is more common in women than in men (Arambepola, Ekanayake, and Fernando 2007; Linhares et al. 2012; Macagnan et al. 2012). One behavioral factor that affects population health is physical activity, as inactivity is related to the increasing prevalence of chronic noncommunicable diseases and appointed as one of the major causes of death worldwide (Lee et al. 2012). Recognizing the importance of the practice of physical activity, a series of recommendations was developed to increase physical activity during various stages of life (World Health Organization [WHO] 2010). Population-based studies have shown that low levels of physical activity, particularly from adolescence to adulthood, are correlated with increased abdominal obesity, especially in women (Hankinson et al. 2010; Tammelin, Laitinen, and Näyhä 2004; Yang et al. 2006). A recent study also reported that higher levels of physical activity independently predicted lower levels of abdominal adiposity regardless of changes in overall body weight (Ekelund et al. 2011). In addition, regular physical activity, particularly in adolescence, may be associated with a physically active lifestyle in adulthood, which helps
Physical Activity and Abdominal Obesity in Women
421
prevent health problems (Hallal et al. 2006). On the other hand, we are unaware of any studies that have examined the relationship between physical activity across the lifespan, especially during adolescence, and abdominal obesity in adulthood among women shift workers. However, shift workers reported more difficulty remaining physically active than other workers, with barriers including lack of time, lack of opportunities, and increased fatigue due to the nature of their work schedules (Atkinson et al. 2008; Kaliterna, Prizmic, and Zganec 2004). Thus, the aim of this study was to examine the association between the practice of physical activities in adolescence and abdominal obesity in adulthood among women shift workers.
METHODS Study Participants An unmatched case-control study was conducted with women from a poultry processing plant that operates 24 hours per day in Southern Brazil. Women who were ≥18 years old and worked a total of 44 hours per week in fixed shifts on the company’s assembly line were included in the study. Poultry processing involves repetitive movements of the upper limbs alternating between sitting and standing positions. The study population was selected from a sample of 1,206 workers who participated in a previous cross-sectional study, conducted at the company in 2010. After removing the men from the sample, all of the women (n = 786) were considered eligible for participation and were enrolled in this case-control study, conducted between January and April 2011. The cases and controls were selected based on anthropometric measures. All of the women with abdominal obesity, defined as a waist circumference greater than or equal to 88 cm (WHO 2008), were identified as cases. In-home interviews were conducted, and the waist circumference of each woman was re-measured to confirm her placement in the case or control group. No women refused to participate. A control group of 1.5 controls per case was selected from the group of women not identified as cases. This control group size increased the precision of the study while taking into account study efficiency and logistical considerations. Women who reported that they were pregnant (at any gestational stage) were excluded from the study because of the changes in their waist circumferences.
Data Collection Information about physical activity and the participants’ demographic, socioeconomic, and occupational characteristics were evaluated using a precoded and pre-tested questionnaire developed by the authors based on standard questionnaires.
422
A. da Silva Garcez et al.
Participation in physical activity was determined using a set of questions about the practice of physical activities in adolescence (until the age of 17 years) and adulthood. This questionnaire was based on an instrument designed to assess lifetime physical activity (Chasan-Taber et al. 2002). Every woman answered about her current participation in physical activities (in adulthood) and in adolescence. The frequency of participation in four domains of physical activity (leisure-time, transportation, domestic, and rural work) was evaluated. Leisure-time included eleven types of physical activities performed for recreation or sport and included walking, running, cycling, volleyball, basketball, handball, soccer, swimming, dance, gymnastics, or other activities. Transportation encompassed two types of physical activity (walking and cycling) performed for at least ten continuous minutes to move from one place to another (e.g., from home to school or work). The domestic and rural work domain had only one question for each, including tasks such as cooking, dishwashing, washing clothes, house cleaning, and gardening for domestic work, and activities such as planting, harvesting, plowing, and raising animals for rural work. For all physical activity items and domains a Likert scale ranging from 0 (never) to 4 (always) was used for responses. An overall score was obtained by summing the number of leisure activities practiced frequently or always and categorizing the number into quartiles (I = 0–1 activity, II = 2 activities, III = 3–4 activities, and IV = 5 or more activities). The value of Cronbach’s α coefficient was 0.635 for questions of the leisure-time physical activity score, with an average inter-item correlation of 0.179. Questions were developed to assess demographic, socioeconomic, and occupational characteristics to characterize the sample, to analyze the distribution of the outcomes and exposures of interest, and to control for confounding and/or interacting factors. The demographic variables included age (collected as a continuous variable and categorized into three age groups), race (self-reported by the interviewees and categorized as white or non-white), and marital status (living with or without a partner). The socioeconomic variables were education (years of study completed, divided into three categories: primary education incomplete—less than 7 years, primary education complete and secondary education incomplete—8 to 10 years, secondary education complete and higher education incomplete or complete—11 or more years) and economic class (categorized using the Economic Classification Criterion of the Brazilian Association of Research Companies—ABEP). This classification criterion estimated the buying power of individuals and families including the possession of household items and the education level of the householder. Occupational characteristics included shift work based on starting time (night: shift beginning between 18:00 and 04:00; day: shift beginning between 05:00 and 14:00) and duration of employment with the company (in completed months, categorized into tertiles). Waist circumference was measured halfway between the last rib
Physical Activity and Abdominal Obesity in Women
423
and the iliac crest using a non-extendable metric measuring tape accurate to 1 mm. Measurements were taken twice for each participant, and the average between the two values was used for the analysis (WHO 2008). All of the women signed an informed consent form accepting to participate in the study, and the study protocol was approved by a Research Ethics Committee (protocol number 3153/2009).
Data Analyses Descriptive statistics were used to describe the sample characteristics comparing cases and controls. The association between abdominal obesity, physical activities, and potential confounding factors were examined using Pearson’s chi-square or Fisher’s exact test for heterogeneity of proportions or linear trend, according to the variable type. Continuous measures were explored by means and standard deviations using Student’s t-test for independent samples. The distribution of physical activities was described by absolute and relative numbers between cases and controls. The domains of physical activity (leisure-time, transportation, domestic and rural work) were analyzed separately because previous studies indicated no interrelationship between the domains of physical activity in relation to the health effects (Abu-Omar and Rütten 2008; Rombaldi et al. 2010). According to the distribution of the data, we investigated the association of leisure-time physical activities with abdominal obesity because it was the only domain that showed variability in the sample. To investigate the association between leisure-time physical activities (categorized into quartiles) and abdominal obesity, an unconditional logistic regression analysis was performed using three models. This analysis demonstrated a good fit, verified by the nonsignificant Hosmer-Lemeshow test (p ≥ .05). Model I was unadjusted, and the other two models were multivariable. Model II was adjusted for demographic variables only, and Model III was adjusted for demographic, socioeconomic, and occupational factors. Just those variables associated with the exposure and the outcome at p < .2 were considered confounding factors and were included in the multivariable analysis. The data analysis was performed using Stata, version 12.0 (StataCorp, College Station, TX, USA).
RESULTS A total of 553 women were selected for the study. Eleven women (2.0 percent) were excluded because they were pregnant, and one (0.2 percent) was excluded because she had an extreme value for her age (60 years old). In the end, 541 women (215 cases and 326 controls) between the ages of 18 and 53 years (average of 33.7 years, Standard Deviation [SD]: ±8.6 years) were included in the analysis. Using a control-to-case ratio of 1.5 and a 95%
424
A. da Silva Garcez et al.
confidence level, the final sample had 80 percent statistical power to detect an odds ratio of 1.83 for the effect of physical activity. A significant difference was observed in the waist circumferences between cases and controls (p < .001), as expected due to the methods to define cases and controls. The average waist circumference was 97.5 cm (SD: ±8.5 cm) among the cases and 78.7 (SD: ±5.7 cm) among the controls, with the minimum and maximum values being 88 and 133 cm among cases and 62.5 and 87.5 cm among controls. A significant difference in age was also observed between cases and controls (p < .001). The average ages of the cases and the controls were 35.2 years (SD: ±8.6 years) and 32.6 years (SD: ±8.4 years), respectively. The minimum and maximum values of age among the cases were 19 and 53 years and among the controls were 18 and 51 years. No difference was observed in waist circumferences between the night and day shift workers (86.3 ± 11.6 cm versus 85.9 ± 11.3 cm, p = .68). Statistically significant differences were also observed in the education levels between the groups of cases and controls (p < .001), with a larger proportion of cases than controls having 7 years of education or less (44.2 percent versus 27.3 percent, respectively). No other significant differences (p ≥ .05) were observed between the cases and the controls in demographic characteristics (Table 1). The number of leisure-time activities decreased in adulthood when compared with the period of adolescence. The controls played soccer significantly more often than the cases both in adolescence (36.8 percent versus 27.9 percent, p = .032) and in adulthood (7.7 percent versus 2.8 percent, p = .017) (Table 2). No statistically significant differences were observed in the frequency of the other leisure-time activities performed by cases and controls. Overall, in adolescence, a higher percentage of the controls participated in leisure-time activities compared to the cases. For both the cases and the controls, the frequency of transportation by bicycle or walking and performing rural work were more prevalent in adolescence. In contrast, the frequency of domestic chores was highly prevalent in both periods of life, with an identical prevalence for both the cases and the controls (Table 2). Based on the score calculated from the number of different leisuretime activities practiced frequently or always in adolescence, in unadjusted analyses, women who participated in five or more physical activities were 50 percent less likely to have abdominal obesity than women who participated in one activity or no physical activities (Odds Ratio [OR] = 0.50; 95% Confidential Interval [95% CI]: 0.27 to 0.89, p = .018). This result remained the same in Model III after adjusting for age, marital status, and education (OR = 0.52; 95% CI: 0.29 to 0.95, p = .033) (Table 3).
Physical Activity and Abdominal Obesity in Women
425
TABLE 1 Demographic, Socioeconomic and Occupational Characteristics of Cases of Abdominal Obesity and Controls Among Women Shift Workers (n = 541) Variables Demographic Age (years) 18 to 30 31 to 40 41 to 53 Race White Other Marital status Without partner With partner Socioeconomic Education (years of school) ≤7 8 to 10 ≥11 Economic class (ABEP)c B (higher) C D (lower) Occupationald Shift work Night shift Day shift Duration of employment (tertile) ≤55 months 56 to 102 months ≥103 months
Casesa (n = 215) n (%)
Controlsa (n = 326) n (%)
76 (35.3) 66 (30.7) 73 (34.0)
153 (47.0) 109 (33.4) 64 (19.6)
192 (89.3) 23 (10.7)
283 (86.8) 43 (13.2)
42 (19.5) 173 (80.5)
82 (25.2) 244 (74.8)
95 (44.2) 37 (17.2) 83 (38.6)
89 (27.3) 67 (20.6) 170 (52.1)
38 (17.7) 167 (77.7) 10 (4.6)
50 (15.3) 257 (78.8) 19 (5.9)
142 (71.4) 57 (28.6)
203 (66.6) 102 (33.4)
73 (36.7) 58 (29.1) 68 (34.2)
97 (31.8) 110 (36.1) 98 (32.2)
p Valueb .001
.386 .128
Physical Activity in Adolescence and Abdominal Obesity in Adulthood: A Case-Control Study Among Women Shift Workers ANDERSON DA SILVA GARCEZ, MS Post-Graduate Program in Collective Health, University of Vale do Rio dos Sinos, São Leopoldo, Brazil
MARIA TERESA ANSELMO OLINTO, PhD Post-Graduate Program in Collective Health, University of Vale do Rio dos Sinos, São Leopoldo; and Department of Nutrition, Federal University of Health Science of Porto Alegre, Porto Alegre, Brazil
RAQUEL CANUTO, PhD Department of Social Medicine, Federal University of Rio Grande do Sul State, Porto Alegre, Brazil
BEATRIZ ANSELMO OLINTO, PhD Post-Graduate Program in History, Unicentro, Paraná, Brazil
MARCOS PASCOAL PATTUSSI, PhD and VERA MARIA VIEIRA PANIZ, PhD Post-Graduate Program in Collective Health, University of Vale do Rio dos Sinos, São Leopoldo, Brazil
Physical activity may have a protective effect against abdominal obesity, an important risk factor for cardiometabolic diseases. Thus, the aim of this study was to examine the association between the practice of physical activities in adolescence and abdominal obesity in adulthood among women shift workers in Southern Brazil in 2011. This case-control study included 215 cases (waist circumference greater than or equal to 88 cm) and 326 controls. For both the case and control groups, participation in leisure-time physical Received November 21, 2013; revised June 4, 2014; accepted June 21, 2014. Address correspondence to Vera Maria Vieira Paniz, PhD, Post-Graduate Program in Collective Health, University of Vale do Rio dos Sinos, Av. Unisinos 950, C.P. 275, São Leopoldo, RS 93022-000, Brazil. E-mail: [email protected] 419
420
A. da Silva Garcez et al.
activities was most frequent in adolescence and was significantly less in adulthood. After adjusting for potential confounding factors, women who participated in five or more physical activities in adolescence were 50 percent less likely to have abdominal obesity than women who participated in one activity or no physical activities (Odds Ratio = 0.50; 95% confidential interval: 0.27–0.93, p value = .029). Participation in various types of leisure-time physical activities in adolescence may protect against abdominal obesity in adulthood, even if the number of physical activities decreases over time. This finding demonstrated the importance of physical activity as well as the period of life in which these should be encouraged for the prevention of health disorders, such as abdominal obesity. KEYWORDS abdominal circumference, women
obesity,
physical
activity,
waist
INTRODUCTION Abdominal obesity is considered one of the most harmful types of obesity because it is an independent risk factor for cardiometabolic diseases (Cameron et al. 2008; Klein et al. 2007). As a result, abdominal obesity has been directly linked to increased overall mortality independent of overall obesity (Jacobs et al. 2010; Pischon et al. 2008). The prevalence of abdominal obesity has increased in recent decades (Visscher and Seidell 2004; Walls et al. 2011), and this condition is more common in women than in men (Arambepola, Ekanayake, and Fernando 2007; Linhares et al. 2012; Macagnan et al. 2012). One behavioral factor that affects population health is physical activity, as inactivity is related to the increasing prevalence of chronic noncommunicable diseases and appointed as one of the major causes of death worldwide (Lee et al. 2012). Recognizing the importance of the practice of physical activity, a series of recommendations was developed to increase physical activity during various stages of life (World Health Organization [WHO] 2010). Population-based studies have shown that low levels of physical activity, particularly from adolescence to adulthood, are correlated with increased abdominal obesity, especially in women (Hankinson et al. 2010; Tammelin, Laitinen, and Näyhä 2004; Yang et al. 2006). A recent study also reported that higher levels of physical activity independently predicted lower levels of abdominal adiposity regardless of changes in overall body weight (Ekelund et al. 2011). In addition, regular physical activity, particularly in adolescence, may be associated with a physically active lifestyle in adulthood, which helps
Physical Activity and Abdominal Obesity in Women
421
prevent health problems (Hallal et al. 2006). On the other hand, we are unaware of any studies that have examined the relationship between physical activity across the lifespan, especially during adolescence, and abdominal obesity in adulthood among women shift workers. However, shift workers reported more difficulty remaining physically active than other workers, with barriers including lack of time, lack of opportunities, and increased fatigue due to the nature of their work schedules (Atkinson et al. 2008; Kaliterna, Prizmic, and Zganec 2004). Thus, the aim of this study was to examine the association between the practice of physical activities in adolescence and abdominal obesity in adulthood among women shift workers.
METHODS Study Participants An unmatched case-control study was conducted with women from a poultry processing plant that operates 24 hours per day in Southern Brazil. Women who were ≥18 years old and worked a total of 44 hours per week in fixed shifts on the company’s assembly line were included in the study. Poultry processing involves repetitive movements of the upper limbs alternating between sitting and standing positions. The study population was selected from a sample of 1,206 workers who participated in a previous cross-sectional study, conducted at the company in 2010. After removing the men from the sample, all of the women (n = 786) were considered eligible for participation and were enrolled in this case-control study, conducted between January and April 2011. The cases and controls were selected based on anthropometric measures. All of the women with abdominal obesity, defined as a waist circumference greater than or equal to 88 cm (WHO 2008), were identified as cases. In-home interviews were conducted, and the waist circumference of each woman was re-measured to confirm her placement in the case or control group. No women refused to participate. A control group of 1.5 controls per case was selected from the group of women not identified as cases. This control group size increased the precision of the study while taking into account study efficiency and logistical considerations. Women who reported that they were pregnant (at any gestational stage) were excluded from the study because of the changes in their waist circumferences.
Data Collection Information about physical activity and the participants’ demographic, socioeconomic, and occupational characteristics were evaluated using a precoded and pre-tested questionnaire developed by the authors based on standard questionnaires.
422
A. da Silva Garcez et al.
Participation in physical activity was determined using a set of questions about the practice of physical activities in adolescence (until the age of 17 years) and adulthood. This questionnaire was based on an instrument designed to assess lifetime physical activity (Chasan-Taber et al. 2002). Every woman answered about her current participation in physical activities (in adulthood) and in adolescence. The frequency of participation in four domains of physical activity (leisure-time, transportation, domestic, and rural work) was evaluated. Leisure-time included eleven types of physical activities performed for recreation or sport and included walking, running, cycling, volleyball, basketball, handball, soccer, swimming, dance, gymnastics, or other activities. Transportation encompassed two types of physical activity (walking and cycling) performed for at least ten continuous minutes to move from one place to another (e.g., from home to school or work). The domestic and rural work domain had only one question for each, including tasks such as cooking, dishwashing, washing clothes, house cleaning, and gardening for domestic work, and activities such as planting, harvesting, plowing, and raising animals for rural work. For all physical activity items and domains a Likert scale ranging from 0 (never) to 4 (always) was used for responses. An overall score was obtained by summing the number of leisure activities practiced frequently or always and categorizing the number into quartiles (I = 0–1 activity, II = 2 activities, III = 3–4 activities, and IV = 5 or more activities). The value of Cronbach’s α coefficient was 0.635 for questions of the leisure-time physical activity score, with an average inter-item correlation of 0.179. Questions were developed to assess demographic, socioeconomic, and occupational characteristics to characterize the sample, to analyze the distribution of the outcomes and exposures of interest, and to control for confounding and/or interacting factors. The demographic variables included age (collected as a continuous variable and categorized into three age groups), race (self-reported by the interviewees and categorized as white or non-white), and marital status (living with or without a partner). The socioeconomic variables were education (years of study completed, divided into three categories: primary education incomplete—less than 7 years, primary education complete and secondary education incomplete—8 to 10 years, secondary education complete and higher education incomplete or complete—11 or more years) and economic class (categorized using the Economic Classification Criterion of the Brazilian Association of Research Companies—ABEP). This classification criterion estimated the buying power of individuals and families including the possession of household items and the education level of the householder. Occupational characteristics included shift work based on starting time (night: shift beginning between 18:00 and 04:00; day: shift beginning between 05:00 and 14:00) and duration of employment with the company (in completed months, categorized into tertiles). Waist circumference was measured halfway between the last rib
Physical Activity and Abdominal Obesity in Women
423
and the iliac crest using a non-extendable metric measuring tape accurate to 1 mm. Measurements were taken twice for each participant, and the average between the two values was used for the analysis (WHO 2008). All of the women signed an informed consent form accepting to participate in the study, and the study protocol was approved by a Research Ethics Committee (protocol number 3153/2009).
Data Analyses Descriptive statistics were used to describe the sample characteristics comparing cases and controls. The association between abdominal obesity, physical activities, and potential confounding factors were examined using Pearson’s chi-square or Fisher’s exact test for heterogeneity of proportions or linear trend, according to the variable type. Continuous measures were explored by means and standard deviations using Student’s t-test for independent samples. The distribution of physical activities was described by absolute and relative numbers between cases and controls. The domains of physical activity (leisure-time, transportation, domestic and rural work) were analyzed separately because previous studies indicated no interrelationship between the domains of physical activity in relation to the health effects (Abu-Omar and Rütten 2008; Rombaldi et al. 2010). According to the distribution of the data, we investigated the association of leisure-time physical activities with abdominal obesity because it was the only domain that showed variability in the sample. To investigate the association between leisure-time physical activities (categorized into quartiles) and abdominal obesity, an unconditional logistic regression analysis was performed using three models. This analysis demonstrated a good fit, verified by the nonsignificant Hosmer-Lemeshow test (p ≥ .05). Model I was unadjusted, and the other two models were multivariable. Model II was adjusted for demographic variables only, and Model III was adjusted for demographic, socioeconomic, and occupational factors. Just those variables associated with the exposure and the outcome at p < .2 were considered confounding factors and were included in the multivariable analysis. The data analysis was performed using Stata, version 12.0 (StataCorp, College Station, TX, USA).
RESULTS A total of 553 women were selected for the study. Eleven women (2.0 percent) were excluded because they were pregnant, and one (0.2 percent) was excluded because she had an extreme value for her age (60 years old). In the end, 541 women (215 cases and 326 controls) between the ages of 18 and 53 years (average of 33.7 years, Standard Deviation [SD]: ±8.6 years) were included in the analysis. Using a control-to-case ratio of 1.5 and a 95%
424
A. da Silva Garcez et al.
confidence level, the final sample had 80 percent statistical power to detect an odds ratio of 1.83 for the effect of physical activity. A significant difference was observed in the waist circumferences between cases and controls (p < .001), as expected due to the methods to define cases and controls. The average waist circumference was 97.5 cm (SD: ±8.5 cm) among the cases and 78.7 (SD: ±5.7 cm) among the controls, with the minimum and maximum values being 88 and 133 cm among cases and 62.5 and 87.5 cm among controls. A significant difference in age was also observed between cases and controls (p < .001). The average ages of the cases and the controls were 35.2 years (SD: ±8.6 years) and 32.6 years (SD: ±8.4 years), respectively. The minimum and maximum values of age among the cases were 19 and 53 years and among the controls were 18 and 51 years. No difference was observed in waist circumferences between the night and day shift workers (86.3 ± 11.6 cm versus 85.9 ± 11.3 cm, p = .68). Statistically significant differences were also observed in the education levels between the groups of cases and controls (p < .001), with a larger proportion of cases than controls having 7 years of education or less (44.2 percent versus 27.3 percent, respectively). No other significant differences (p ≥ .05) were observed between the cases and the controls in demographic characteristics (Table 1). The number of leisure-time activities decreased in adulthood when compared with the period of adolescence. The controls played soccer significantly more often than the cases both in adolescence (36.8 percent versus 27.9 percent, p = .032) and in adulthood (7.7 percent versus 2.8 percent, p = .017) (Table 2). No statistically significant differences were observed in the frequency of the other leisure-time activities performed by cases and controls. Overall, in adolescence, a higher percentage of the controls participated in leisure-time activities compared to the cases. For both the cases and the controls, the frequency of transportation by bicycle or walking and performing rural work were more prevalent in adolescence. In contrast, the frequency of domestic chores was highly prevalent in both periods of life, with an identical prevalence for both the cases and the controls (Table 2). Based on the score calculated from the number of different leisuretime activities practiced frequently or always in adolescence, in unadjusted analyses, women who participated in five or more physical activities were 50 percent less likely to have abdominal obesity than women who participated in one activity or no physical activities (Odds Ratio [OR] = 0.50; 95% Confidential Interval [95% CI]: 0.27 to 0.89, p = .018). This result remained the same in Model III after adjusting for age, marital status, and education (OR = 0.52; 95% CI: 0.29 to 0.95, p = .033) (Table 3).
Physical Activity and Abdominal Obesity in Women
425
TABLE 1 Demographic, Socioeconomic and Occupational Characteristics of Cases of Abdominal Obesity and Controls Among Women Shift Workers (n = 541) Variables Demographic Age (years) 18 to 30 31 to 40 41 to 53 Race White Other Marital status Without partner With partner Socioeconomic Education (years of school) ≤7 8 to 10 ≥11 Economic class (ABEP)c B (higher) C D (lower) Occupationald Shift work Night shift Day shift Duration of employment (tertile) ≤55 months 56 to 102 months ≥103 months
Casesa (n = 215) n (%)
Controlsa (n = 326) n (%)
76 (35.3) 66 (30.7) 73 (34.0)
153 (47.0) 109 (33.4) 64 (19.6)
192 (89.3) 23 (10.7)
283 (86.8) 43 (13.2)
42 (19.5) 173 (80.5)
82 (25.2) 244 (74.8)
95 (44.2) 37 (17.2) 83 (38.6)
89 (27.3) 67 (20.6) 170 (52.1)
38 (17.7) 167 (77.7) 10 (4.6)
50 (15.3) 257 (78.8) 19 (5.9)
142 (71.4) 57 (28.6)
203 (66.6) 102 (33.4)
73 (36.7) 58 (29.1) 68 (34.2)
97 (31.8) 110 (36.1) 98 (32.2)
p Valueb .001
.386 .128
