Background:
Obesity is associated with excessive daytime sleepiness, but causality remains unclear. Through a causal framework, we aim to assess the effect of weight change on daytime sleepiness, and the role of obstructive sleep apnea (OSA) in this relationship.
Methods:
From the Sleep Heart Health Study, we selected individuals who were: 1) 40 to 64 years old, with 2) body mass index (BMI) ≥18.5 kg/m2, 3) no history of stroke, treatment for OSA, and tracheostomy at baseline. We used multiple linear regression to assess the relationship between 5-year weight change and daytime sleepiness (assessed through Epworth Sleepiness Scale (ESS)) at 5 years, adjusting for potential confounders, in those with complete data (n=1,468). Potential confounders were identified through a directed acyclic graph, which include daytime sleepiness, demographics, diabetes, subjective sleep duration, sleep disturbance, smoking status, weight, and use of antidepressants and benzodiazepines at baseline. We further assessed the potential mediating role of OSA, physical health, mental health, and sleep duration in the relationship between weight change and daytime sleepiness.
Results:
At baseline, the study participants were on average 55 years old, 46% males, with mean BMI 28 kg/m2; and 25% had ESS>10. ESS at 5 years worsened by 0.36 units (95%CI 0.12 – 0.61, P=0.004) with every 10 kg weight gain. When stratified by sex, this relationship was only found in women (0.55, 95%CI 0.25-0.86, p<0.001; p-interaction=0.02). Approximately one-fifth of the relationship between weight change and daytime sleepiness was mediated by severity of OSA at 5 years, and around one-sixth by poor physical health.
Conclusions:
Weight gain has a detrimental effect on daytime sleepiness, mostly through pathways other than OSA. This study provides further evidence and understanding to the relationship between obesity and excessive daytime sleepiness, which may help in the management of obesity-related EDS.