Sleep symptoms predict the development of the metabolic syndrome

Abstract

Background: Sleep complaints are highly prevalent and associated with cardiovascular disease (CVD) morbidity and mortality. This is the first prospective study to report the association between commonly reported sleep symptoms and the development of the metabolic syndrome, a key CVD risk factor.

Methods: Participants were from the community-based Heart Strategies Concentrating on Risk Evaluation study. The sample was comprised of 812 participants (36% African American; 67% female) who were free of metabolic syndrome at baseline, had completed a baseline sleep questionnaire, and had metabolic syndrome evaluated 3 years after baseline. Apnea-hypopnea index (AHI) was measured cross-sectionally using a portable monitor in a subset of 290 participants. Logistic regression examined the risk of developing metabolic syndrome and its components according to individual sleep symptoms and insomnia syndrome.

Results: Specific symptoms of insomnia (difficulty falling asleep [DFA] and "unrefreshing" sleep), but not a syndromal definition of insomnia, were significant predictors of the development of metabolic syndrome. Loud snoring more than doubled the risk of developing the metabolic syndrome and also predicted specific metabolic abnormalities (hyperglycemia and low high-density lipoprotein cholesterol). With further adjustment for AHI or the number of metabolic abnormalities at baseline, loud snoring remained a significant predictor of metabolic syndrome, whereas DFA and unrefreshing sleep were reduced to marginal significance.

Conclusion: Difficulty falling asleep, unrefreshing sleep, and, particularly, loud snoring, predicted the development of metabolic syndrome in community adults. Evaluating sleep symptoms can help identify individuals at risk for developing metabolic syndrome.

Keywords: Metabolic syndrome; insomnia, cardiovascular risk; sleep-disordered breathing.

Figure 1

Odds of developing the metabolic syndrome according to sleep symptoms with covariate adjustment. Filled diamonds depict adjusted odds ratios of developing the metabolic syndrome; filled circles depict lower and upper 95% confidence limits. Odds ratios are adjusted for age, sex, race (white/black), marital status (married/unmarried), study randomization, smoking status (ever/never), alcohol consumption (0-3 drinks per week/4 or more drinks per week), sedentary lifestyle (yes/no), and presence of clinically significant depressive symptoms (yes/no).

Figure 2

Effect of insomnia symptoms and loud snoring on metabolic syndrome incidence, with and without adjustment for AHI. Filled diamonds depict adjusted odds ratios of developing the metabolic syndrome; filled circles depict lower and upper 95% confidence limits. Odds ratios are adjusted for age, sex, race (white/black), marital status (married/unmarried), smoking status (ever/never), alcohol consumption (0-3 drinks per week/4 or more drinks per week), sedentary lifestyle (yes/no), and presence of clinically significant depressive symptoms (yes/no). AHI refers to Apnea Hypopnea Index (continuous, with n = 4 outliers removed). N for Models 1 and 2 = 805 due to missing data. N for Model 3 = 290 (subsample with AHI).