Daily sleep duration and the risk of incident disability among younger elderly Japanese adults in the New Integrated Suburban Seniority Investigation Project: A prospective study using competing event analysis

Aim This study aimed to investigate the association between daily sleep duration and incident disability among younger elderly individuals in Japan. Methods We carried out a prospective cohort study, the New Integrated Suburban Seniority Investigation Project, including 1895 (962 men and 933 women) Japanese physically and socially independent individuals aged ≥65 years. Information on daily sleep duration, demographic, lifestyle characteristics and medical status were collected by questionnaire and health checkup every year from 1996 through 2005. Dates of incident disability were confirmed using the certification for the long‐term care insurance in Japan. We treated censored cases due to death as competing events. A competing risk model was used to calculate the hazard ratio and 95% confidence interval for incident disability. Results During a median of 12.7 years of follow up, 256 participants (114 men and 142 women) reported incident disability. Compared with a sleep duration of 7–7.9 h/day, sleeping