Introduction: This study was conducted to evaluate the association between self-reported sleep characteristics and rapid decline of estimated glomerular filtration rate (eGFR) in adults with initially normal kidney function.

Methods: Data from participants in the reevaluation phase of the Fasa Adult Cohort Study (FACS) were analyzed. Rapid eGFR decline was defined as an annual decrease > 3 ml/min per 1.73 m² and rapid eGFR percent decline was defined as an annual decrease > 10th percentile of study sample. Daily sleep duration, daytime napping, sleep onset latency (SOL), the use of sleeping pills and daytime sleepiness were assessed at baseline through interviews conducted by trained nurses. Poisson regression models were applied to evaluate the risk of outcomes across sleep characteristics.

Results: A total of 2810 participants, of whom 53.7% were female, with a mean age of 49.8 (± 8.3) yrs and a baseline eGFR of 88.5 (± 10.6) were studied. Regular daytime napping was associated with a reduced risk of rapid eGFR decline in individuals aged > 50 yrs (adjusted relative risk [RR]: 0.64, 95% confidence interval [CI]: 0.48-0.86). Specifically, naps exceeding 90 minutes daily were associated with a 49% reduced risk compared with nonnappers (adjusted RR: 0.51, 95% CI: 0.33-0.81). Among participants aged < 50 yrs, sleeping < 7 h/d was linked to a higher likelihood of rapid eGFR percent decline (adjusted RR:1.78, 95% CI: 1.12-2.82).

Conclusion: Regular daytime napping, especially in older adults, may be protective against kidney function decline, whereas short sleep duration may accelerate eGFR decline in younger adults. Addressing sleep habits may aid in preventing chronic kidney disease (CKD).