Nonrestorative sleep is a risk factor for metabolic syndrome in the general Japanese population

BACKGROUND: This longitudinal study aimed to investigate the effects of nonrestorative sleep on developing metabolic syndrome (MetS) and related diseases in a general Japanese middle-aged population. METHODS: Overall, 83,224 adults without MetS (mean age: 51.5 ± 3.5 years) from the Health Insurance Association in Japan were followed up for a maximum of 8 years between 2011 and 2019. The Cox proportional hazard method was used to determine whether nonrestorative sleep, assessed using a single-item question, was significantly associated with the respective development of MetS, obesity, hypertension, diabetes, and dyslipidemia. The MetS criteria were adopted by the Examination Committee for Criteria of Metabolic Syndrome in Japan. RESULTS: The mean follow-up duration was 6.0 years. The incidence rate of MetS was 50.1 person-years/1,000 during the study period. Data suggested that nonrestorative sleep was associated with MetS (hazard ratio [HR]: 1.12, 95% confidence interval [CI]: 1.08–1.16) and other disorders, such as obesity (HR: 1.07, 95% CI: 1.02–1.12), hypertension (HR: 1.07, 95% CI: 1.04–1.11), and diabetes (HR: 1.07, 95% CI: 1.01–1.12) but not with dyslipidemia (HR: 1.00, 95% CI: 0.97–1.03). CONCLUSIONS: Nonrestorative sleep is associated with the development of MetS and many of its core components in the middle-aged Japanese population. Therefore, assessing nonrestorative sleep may help identify individuals at a risk of MetS development. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13098-023-00999-x.