JOURNAL OF CAFFEINE RESEARCH Volume 4, Number 1, 2014 ª Mary Ann Liebert, Inc. DOI: 10.1089/jcr.2013.0029
Eveningness Chronotype, Daytime Sleepiness, Caffeine Consumption, and Use of Other Stimulants Among Peruvian University Students Anjalene Whittier,1 Sixto Sanchez,2,3 Benjamı´n Castan˜eda,2 Elena Sanchez,3 Bizu Gelaye,1 David Yanez,4 and Michelle A. Williams1
Objectives: The aims of this study were to evaluate patterns of circadian preferences and daytime sleepiness, and to examine the extent to which the consumption of stimulant beverages is associated with daytime sleepiness and evening chronotype among Peruvian college-age students. Methods: A total of 2,581 undergraduate students completed a self-administered comprehensive questionnaire that gathered information about sleep habits, sociodemographic and lifestyle characteristics, and the use of caffeinated beverages. The Morningness–Eveningness Questionnaire (MEQ) and Epworth Sleepiness Scale (ESS) were used to assess chronotype and daytime sleepiness. We used multivariable linear and logistic regression procedures to estimate odds ratios (OR) and 95% confidence intervals (95% CI) for the associations of sleep disorders with sociodemographic and behavioral factors. Results: The prevalence of daytime sleepiness was 35% [95% CI 32.7–36.4] and eveningness chronotype was 10% [95% CI 8.8–11.1%]. Age, sex, cigarette smoking, and alcohol consumption were significantly associated with an evening chronotype. After adjusting for age, sex, smoking, body mass index, and physical activity, students who reported consumption of any stimulant beverages had 1.25 increased odds of excessive daytime sleepiness (OR = 1.25 [95% CI 1.03–1.53]) compared with students who did not consume stimulant beverages. Consumption of any stimulant beverages was not statistically significantly associated with being an evening chronotype (OR = 1.30 [95% CI 0.86–1.96]). Conclusions: Excessive daytime sleepiness and eveningness chronotype are common among Peruvian college students. MEQ scores were associated with age, sex, smoking, and alcohol consumption. Regular stimulant beverage consumption tended to be positively associated with excessive daytime sleepiness.
thermore, studies have shown that among Peruvian medical students, 58–74% have reported poor sleep quality and 26– 34% have reported excessive daytime sleepiness, with several students also reporting consuming caffeine and tobacco and using sleep aids.11,12 Roehrs and Roth13 suggested a bidirectional relationship of caffeine and daytime sleepiness. Namely, the authors noted that poor sleep quality can lead to caffeine consumption to combat sleepiness, which can in turn negatively impact sleep quality and increase sleepiness.13 Lund et al.14 noted that individuals in a ‘‘stimulant–sedation loop’’ may be at higher risk for developing a drug dependency. An emerging body of evidence has shown the impact of caffeinated drinks in disrupting an individual’s preferred sleep timing or chronotype.15 Sleep timing depends on both the length of prior wakefulness (homeostasis) and
Introduction
I
nsufficient sleep—sleep of shorter duration than the average 7–8 hours per night—negatively impacts many areas of life, including cognition, performance, safety, and health.1–3 In a recent multi-country sleep study, high levels of poor sleep quality were reported among Peruvian, Thai, Ethiopian, and Chilean university students.4–7 Each of the populations studied showed associations between poor sleep and the consumption of stimulant beverages.4–7 Taylor and Bramoweth8 found that 60% of university-age students reported consuming stimulant beverages (e.g., sodas and coffee) to combat daytime sleepiness.8 Approximately 96% of Peruvian medical students reported regular consumption of caffeinated drinks,9 and 34% of them reported using energy drinks.10 Fur1
Department of Epidemiology, Multidisciplinary International Research Training Program, Harvard School of Public Health, Boston, Massachusetts. 2 Universidad de San Martin de Porres, Lima, Peru. 3 Asociacion Civil Proyectos en Salud (PROESA), Lima, Peru. 4 Department of Biostatistics, University of Washington, Seattle, Washington.
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on the control of the circadian clock. Circadian clocks synchronize with their environment predominantly with the light–dark cycle of day and night.16 Three chronotypes have been identified—morningness, intermediate, and eveningness—and are based on peak times of day according to one’s circadian rhythm.17 Individuals classified with an evening chronotype have significantly later peak times than those with a morning chronotype.17 Taillard et al.18 noted that evening chronotypes: need more sleep, spend less time in bed during the week, spend more time in bed during the weekend, have generally more irregular sleep habits, and consume more caffeinated drinks.18 Nova et al.19 found that caffeinated drinks do not appear to affect wake after sleep onset in those with an evening chronotype. Evening chronotypes are associated with increased risk of behavioral problems, lower self-esteem, hyperactivity, and psychiatric disorders.20,21 Those with an evening chronotype are also more likely to have respiratory syndromes, bronchial asthma, and a higher body mass index (BMI).20,22 For university-age students, an evening chronotype has been positively associated with cognitive ability, and negatively associated with indicators of academic achievement.23 Eveningness preference compared with morningness has been associated with the consumption of alcoholic drinks, stimulants, and cigarettes.21,24,25 University students who use energy drinks and other caffeinated beverages have been associated with more sleep disturbances than those who do not use them.5,6,21 Although caffeine is the primary ingredient in energy drinks, some popular brands are more caffeinated; Red Bull, for instance, contains 80 mg of caffeine per serving.26 Energy drinks also contain additional ingredients that may have a stimulating effect. Commonly stated reasons for using stimulants included improving work performance and concentration, even though stimulant usage has been associated with lower grade-point averages.26,27 Given the increased consumption of energy drinks among college students and the limited studies6 that evaluate their possible adverse impact on sleep disorders among young Peruvian adults, we conducted this study to evaluate patterns of circadian rhythm characteristics and daytime sleepiness and to examine the extent to which the consumption of caffeinated beverages is associated with the evening chronotype and daytime sleepiness among Peruvian college-age students. Methods and Materials Study population
The data used in this study were collected from undergraduate students at the Universidad Nacional Mayor de San Marcos and the Universidad San Martin de Porres in Lima, Peru, from November 2010 through May 2011 as part of a larger, multi-country sleep study. A more detailed description of the study’s procedures including data collection, setting, and the study design has been provided previously.6 Individuals with missing information on sleep characteristics and energy drinks were excluded from the analyses. The final study sample used in the analyses included 2,581 students (1,579 female and 1,002 male). The procedures used in this study were approved by the institutional review boards of Dos de Mayo Hospital and Universidad Nacional Mayor de San Marcos in Lima, Peru, and the University of Washington, Seattle, WA. The Harvard School of Public Health Office of
WHITTIER ET AL.
Human Research Administration granted approval to use the de-identified data set for analysis. Data collection
Anonymous, self-administered surveys were given to participants to complete without time limits. Questions included demographic information and behavioral risk factors (e.g., cigarette smoking status, alcohol consumption, energy drink consumption, coffee consumption). After survey completion, trained research staff took measurements of participants’ waist, height, hip, and weight measurements in order to compute BMI values and other anthropometric measurements. Variable specification
Stimulant beverage consumption was defined as the usage of one or more caffeinated beverages (e.g., Coca-Cola, Pepsi, coffee) or energy drinks (e.g., Red Bull, Evolution, Turbo, Maretazo, Shark, Burn) per week during the past month. Participants were asked about their levels of alcohol consumption (
Eveningness Chronotype, Daytime Sleepiness, Caffeine Consumption, and Use of Other Stimulants Among Peruvian University Students Anjalene Whittier,1 Sixto Sanchez,2,3 Benjamı´n Castan˜eda,2 Elena Sanchez,3 Bizu Gelaye,1 David Yanez,4 and Michelle A. Williams1
Objectives: The aims of this study were to evaluate patterns of circadian preferences and daytime sleepiness, and to examine the extent to which the consumption of stimulant beverages is associated with daytime sleepiness and evening chronotype among Peruvian college-age students. Methods: A total of 2,581 undergraduate students completed a self-administered comprehensive questionnaire that gathered information about sleep habits, sociodemographic and lifestyle characteristics, and the use of caffeinated beverages. The Morningness–Eveningness Questionnaire (MEQ) and Epworth Sleepiness Scale (ESS) were used to assess chronotype and daytime sleepiness. We used multivariable linear and logistic regression procedures to estimate odds ratios (OR) and 95% confidence intervals (95% CI) for the associations of sleep disorders with sociodemographic and behavioral factors. Results: The prevalence of daytime sleepiness was 35% [95% CI 32.7–36.4] and eveningness chronotype was 10% [95% CI 8.8–11.1%]. Age, sex, cigarette smoking, and alcohol consumption were significantly associated with an evening chronotype. After adjusting for age, sex, smoking, body mass index, and physical activity, students who reported consumption of any stimulant beverages had 1.25 increased odds of excessive daytime sleepiness (OR = 1.25 [95% CI 1.03–1.53]) compared with students who did not consume stimulant beverages. Consumption of any stimulant beverages was not statistically significantly associated with being an evening chronotype (OR = 1.30 [95% CI 0.86–1.96]). Conclusions: Excessive daytime sleepiness and eveningness chronotype are common among Peruvian college students. MEQ scores were associated with age, sex, smoking, and alcohol consumption. Regular stimulant beverage consumption tended to be positively associated with excessive daytime sleepiness.
thermore, studies have shown that among Peruvian medical students, 58–74% have reported poor sleep quality and 26– 34% have reported excessive daytime sleepiness, with several students also reporting consuming caffeine and tobacco and using sleep aids.11,12 Roehrs and Roth13 suggested a bidirectional relationship of caffeine and daytime sleepiness. Namely, the authors noted that poor sleep quality can lead to caffeine consumption to combat sleepiness, which can in turn negatively impact sleep quality and increase sleepiness.13 Lund et al.14 noted that individuals in a ‘‘stimulant–sedation loop’’ may be at higher risk for developing a drug dependency. An emerging body of evidence has shown the impact of caffeinated drinks in disrupting an individual’s preferred sleep timing or chronotype.15 Sleep timing depends on both the length of prior wakefulness (homeostasis) and
Introduction
I
nsufficient sleep—sleep of shorter duration than the average 7–8 hours per night—negatively impacts many areas of life, including cognition, performance, safety, and health.1–3 In a recent multi-country sleep study, high levels of poor sleep quality were reported among Peruvian, Thai, Ethiopian, and Chilean university students.4–7 Each of the populations studied showed associations between poor sleep and the consumption of stimulant beverages.4–7 Taylor and Bramoweth8 found that 60% of university-age students reported consuming stimulant beverages (e.g., sodas and coffee) to combat daytime sleepiness.8 Approximately 96% of Peruvian medical students reported regular consumption of caffeinated drinks,9 and 34% of them reported using energy drinks.10 Fur1
Department of Epidemiology, Multidisciplinary International Research Training Program, Harvard School of Public Health, Boston, Massachusetts. 2 Universidad de San Martin de Porres, Lima, Peru. 3 Asociacion Civil Proyectos en Salud (PROESA), Lima, Peru. 4 Department of Biostatistics, University of Washington, Seattle, Washington.
21
22
on the control of the circadian clock. Circadian clocks synchronize with their environment predominantly with the light–dark cycle of day and night.16 Three chronotypes have been identified—morningness, intermediate, and eveningness—and are based on peak times of day according to one’s circadian rhythm.17 Individuals classified with an evening chronotype have significantly later peak times than those with a morning chronotype.17 Taillard et al.18 noted that evening chronotypes: need more sleep, spend less time in bed during the week, spend more time in bed during the weekend, have generally more irregular sleep habits, and consume more caffeinated drinks.18 Nova et al.19 found that caffeinated drinks do not appear to affect wake after sleep onset in those with an evening chronotype. Evening chronotypes are associated with increased risk of behavioral problems, lower self-esteem, hyperactivity, and psychiatric disorders.20,21 Those with an evening chronotype are also more likely to have respiratory syndromes, bronchial asthma, and a higher body mass index (BMI).20,22 For university-age students, an evening chronotype has been positively associated with cognitive ability, and negatively associated with indicators of academic achievement.23 Eveningness preference compared with morningness has been associated with the consumption of alcoholic drinks, stimulants, and cigarettes.21,24,25 University students who use energy drinks and other caffeinated beverages have been associated with more sleep disturbances than those who do not use them.5,6,21 Although caffeine is the primary ingredient in energy drinks, some popular brands are more caffeinated; Red Bull, for instance, contains 80 mg of caffeine per serving.26 Energy drinks also contain additional ingredients that may have a stimulating effect. Commonly stated reasons for using stimulants included improving work performance and concentration, even though stimulant usage has been associated with lower grade-point averages.26,27 Given the increased consumption of energy drinks among college students and the limited studies6 that evaluate their possible adverse impact on sleep disorders among young Peruvian adults, we conducted this study to evaluate patterns of circadian rhythm characteristics and daytime sleepiness and to examine the extent to which the consumption of caffeinated beverages is associated with the evening chronotype and daytime sleepiness among Peruvian college-age students. Methods and Materials Study population
The data used in this study were collected from undergraduate students at the Universidad Nacional Mayor de San Marcos and the Universidad San Martin de Porres in Lima, Peru, from November 2010 through May 2011 as part of a larger, multi-country sleep study. A more detailed description of the study’s procedures including data collection, setting, and the study design has been provided previously.6 Individuals with missing information on sleep characteristics and energy drinks were excluded from the analyses. The final study sample used in the analyses included 2,581 students (1,579 female and 1,002 male). The procedures used in this study were approved by the institutional review boards of Dos de Mayo Hospital and Universidad Nacional Mayor de San Marcos in Lima, Peru, and the University of Washington, Seattle, WA. The Harvard School of Public Health Office of
WHITTIER ET AL.
Human Research Administration granted approval to use the de-identified data set for analysis. Data collection
Anonymous, self-administered surveys were given to participants to complete without time limits. Questions included demographic information and behavioral risk factors (e.g., cigarette smoking status, alcohol consumption, energy drink consumption, coffee consumption). After survey completion, trained research staff took measurements of participants’ waist, height, hip, and weight measurements in order to compute BMI values and other anthropometric measurements. Variable specification
Stimulant beverage consumption was defined as the usage of one or more caffeinated beverages (e.g., Coca-Cola, Pepsi, coffee) or energy drinks (e.g., Red Bull, Evolution, Turbo, Maretazo, Shark, Burn) per week during the past month. Participants were asked about their levels of alcohol consumption (
