Background: Sleep duration affects health in various ways. The objective of the present study was to investigate the relationships among sleep duration, daytime napping and kidney function in a middle-aged apparently healthy Chinese population.
Methods: According to self-reported total sleep and daytime napping durations, 33,850 participants who were 38-90 years old and recruited from eight regional centers were divided into subgroups. Height, weight, waist circumference, hip circumference, blood pressure, biochemical indexes, fasting blood glucose (FBG), postprandial blood glucose (PBG), HbA1c, creatinine and urinary albumin-creatinine ratio (UACR) were measured and recorded for each subject. Microalbuminuria was defined as UACR ≥30 mg/g, chronic kidney disease (CKD) was defined as eGFR <60 ml/min, and hyperfiltration was defined as eGFR ≥135 ml/min. Multiple logistic regression was applied to investigate the association between sleep and kidney function.
Results: Compared to sleeping for 7-8 h/day, the ORs for microalbuminuria for sleeping for >9 h/day, 8-9 h/day 6-7 h/day and <6 h/day were 1.343 (1.228-1.470, P<0.001), 1.223 (1.134-1.320, P<0.001), 1.130 (1.003-1.273, P = 0.045) and 1.140 (0.908-1.431, P = 0.259), respectively. The eGFR levels exhibited a U-shaped association with sleep duration among subjects with an eGFR ≥90 ml/min and an N-shaped association with sleep duration among subjects with an eGFR <90 ml/min. The OR for hyperfiltration for >9 h/day of sleep was 1.400 (1.123-1.745, P = 0.003) among participants with an eGFR ≥90 ml/min. Daytime napping had a negative effect on renal health. Compared to the absence of a napping habit, the ORs for microalbuminuria for 0-1 h/day, 1-1.5 h/day and >1.5 h/day of daytime napping were 1.552 (1.444-1.668, P<0.001), 1.301 (1.135-1.491, P<0.001) and 1.567 (1.353-1.814, P<0.001), respectively.
Conclusion: The association of total sleep duration with renal health outcomes is U-shaped. Daytime napping has a negative effect on renal health.