The aim of this study was to clarify an association between short sleep duration and smoking initiation.

Participants eligible for this retrospective cohort study were university students who were admitted to a single national university in Japan between 2007 and 2015. Baseline sleep duration and smoking status were measured using general questionnaires at health checkups at admission. During a 6-year observation period, smoking initiation was assessed using general questionnaires at annual health checkups. Cox proportional hazards models adjusted for clinically relevant factors were used to assess the association between sleep duration and smoking initiation.

Of 17,493 men, including 540, 5,568, 8,458, 2,507, and 420 men with sleep duration of < 5, 5–6, 6–7, 7–8, and ≥ 8 h, respectively, smoking initiation was observed in 16.1%, 12.5%, 11.2%, 10.0%, and 11.7%, respectively, during a median observation period of 3.0 years. Men with shorter sleep duration were at a higher risk of smoking initiation (adjusted hazard ratio 1.49 [95% confidence interval 1.19–1.85], 1.11 [1.01–1.22], 1.00 [reference], 0.92 [0.80–1.06], and 1.00 [0.75–1.34], respectively). Of 8,880 women, including 267, 3,163, 4,220, and 1,230 women with sleep duration of < 5, 5–6, 6–7, and ≥ 7 h, respectively, smoking initiation was observed in 4.9%, 2.3%, 2.0%, and 2.2%, respectively, during a median observation period of 3.0 years. A similar dose dependent association was ascertained in women (2.50 [1.39–4.49], 1.18 [0.86–1.62], 1.00 [reference], and 1.22 [0.79–1.89], respectively).

This study clarified that university students with short sleep duration were vulnerable to smoking initiation.