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 [greater than or equal to]30 mg/g, chronic kidney disease (CKD) was defined as eGFR 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 1.5 h/day of daytime napping were 1.552 (1.444-1.668, P Conclusion The association of total sleep duration with renal health outcomes is U-shaped. Daytime napping has a negative effect on renal health.