Causal relationship of sleep duration on risks for metabolic syndrome: a Mendelian randomization study

The cluster of cardiovascular risk factors, referred to as metabolic syndrome (MetS), represents a substantial risk factor for cardiovascular diseases and presents a significant public health challenge. However, previous epidemiological investigations exploring the link between sleep duration and MetS lack experimental evidence to establish a causal relationship. Hence, he objective of this study is to examine the association between sleep duration and MetS by employing the Mendelian randomization (MR) approach.

A cross-sectional study was conducted utilizing the Taiwan Biobank database, which comprised 33,270 predominantly Han Chinese individuals aged 30-70 years with no history of cancer and enrolled between 2008 and 2020. This study was conducted using Taiwan Biobank database. In MR analysis, we constructed weighted and unweighted genetic risk scores by calculating the SNP alleles significantly associated with sleep duration. Two-stage regression analysis was used to estimate odds ratio (OR) and 95% confidence interval (CI).

In the observational epidemiologic study, after multivariate adjustment, the OR for sleep durations of < 5, 8-9 and > 9 h compared to those with a sleep duration of 7 h were 1.23 (95% CI: 1.07, 1.43), 1.15 (95% CI: 1.06, 1.24) and 1.84 (95% CI: 1.43, 2.36), respectively. In the MR analyses after multivariate adjustment, the ORs of MetS per 1 standard deviation increase in the estimated sleep duration and the probability of long and short sleep durations derived from weighted genetic risk scores were 0.64 (95% CI: 0.63, 0.66), 1.55 (95% CI: 1.51, 1.59), and 1.66 (95% CI: 1.62, 1.70), respectively.

Observational and MR analyses demonstrated that short and long sleep durations are potential causal risk factors for MetS. Therefore, long and short sleep durations should be considered as risk factors in MetS-prevention strategies.