The Influence of Age and Gender on the Relationship between Sleep Duration and Metabolic Syndrome in Korean Adults

Abstract

ObjectiveA growing number of studies have reported that both short and long sleep duration are associated with an increased risk for abdominal obesity, dyslipidemia, raised blood pressure, glucose dysregulation. The latter being the components of metabolic syndrome, it is of interest the relationship that sleep duration has on the development of metabolic syndrome. Previous studies performed on the Korean adult population found short and long sleep duration to be related to an increased risk of metabolic syndrome. However, these analyses were done utilizing a limited number of participants and were not age- or gender-specific. The present study evaluated the effect of sleep duration on prevalent metabolic syndrome in Korean adults utilizing nationally representative data, and investigated if gender and age modify this relationship.MethodsA cross-sectional analysis of the Korean National Health and Nutrition Examination Survey was performed on a final population of 24,511 participants (59.2% female) aged 20-79 years. Sleep duration was categorized into five groups: ≤ 5, 6, 7 (referent), 8, and ≥ 9 h/day. The effect of age and sex on the relationship between sleep and metabolic syndrome was investigated using the log likelihood test. The ages of men and women were categorized into 20-39 y, 40-59 y, and 60-79 y after discovering age was a significant effect modifier. Logistic regression analysis was used to test the hypothesis that sleep duration is significantly associated with the presence of metabolic syndrome in adults.ResultsThe prevalence of metabolic syndrome by sleep category demonstrated a U-shaped pattern among the total population. Women sleeping ≤ 5 h/day had the highest prevalence compared to 7 h/day (36% vs. 21%). After adjustment for potential confounders, women sleeping ≥ 9 h/day had a 1.43 times higher odds (95% CI, 1.18-1.74) of prevalent metabolic syndrome compared to those sleeping 7 h/day. Young women (20-39y) sleeping ≥ 9 h/day were the most likely to have metabolic syndrome with a 2.13 higher odds (95% CI, 1.38-3.38) compared with young women sleeping 7 h/day. The relationship persisted in middle-aged women (40-59y) who were long sleepers (OR = 1.63; 95% CI 1.21-2.21). Only in the total male population was there an increased risk for metabolic syndrome if sleeping ≥ 9 h/day (OR = 1.26; 95% CI 1.01-1.57).ConclusionThese data suggest that sleep duration is associated with metabolic syndrome; however, age and gender significantly modify the relationship. For the total population, long and short sleep duration was associated with metabolic syndrome in the unadjusted model. However, the relationship only remained significant for long sleepers after adjusting for significant confounding variables. Young and middle aged women were found to be at increased odds of metabolic syndrome if sleeping long hours. Short sleep duration was not associated with metabolic syndrome in this study population. Additional studies are needed to investigate the temporal relationship between these measures in the Korean population.