Longitudinal relationship between long sleep duration and future kidney function decline

Background: Evidence linking chronic kidney disease (CKD) and sleep duration is inconsistent. This study examined whether sleep duration is associated with a long-term risk of kidney function decline. Methods: This retrospective, longitudinal cohort study included 82 001 participants who visited a primary care centre in Japan. Participants were categorized into CKD risk groups and sleep duration categories according to their self-reported average nightly sleep duration. The relationship between average nightly sleep duration and the incidence of composite renal outcome comprised a ≥40% reduction in estimated glomerular filtration rate (eGFR) from baseline and a decline in eGFR to <15 mL/min/1.73 m² was evaluated. Results: The mean age and eGFR (±standard deviation) of the patient cohort were 45.8 (±12.4) years and 81.8 (±15.4) mL/min/1.73 m², respectively. A total of 41 891 participants (51.1%) were women. During the median follow-up of 5.1 years [interquartile range 2.2-9.6], 4214 (5.1%) participants achieved the composite renal outcome. Only the long and very long sleep durations (≥8 h/night) were associated with an increased incidence of the composite renal outcome compared with the reference duration (7 h/night) [adjusted odds ratio (OR) 1.22 and 1.44; 95% confidence interval (CI) 1.09-1.36 and 1.13-1.84, for long and very long sleep durations, respectively]. Furthermore, this association was significant for both long and very long sleep durations in the low CKD risk group but only for long sleep duration in the intermediate CKD risk group. The results of the sex-specific analysis showed that men had a decreased risk of achieving the composite renal outcome (OR 0.91; 95% CI 0.79-1.06), while there was an increased risk for women (OR 1.14; 95% CI 1.02-1.28). Conclusions: Average sleep durations ≥8 h/night were associated with an increased incidence of poor renal outcomes over time. However, a longitudinal cohort study is required to confirm whether sleep duration can prevent poor renal outcomes.