The start of smoking and prior lifestyles among Japanese college students: a retrospective cohort study.

INTRODUCTION

Using annual health checkup questionnaire data, the present study aimed to explore the relationship between lifestyles and subsequent new smoking of college students.

METHODS

Among the all undergraduate students who entered Kyoto University from 2000 through 2004, those who had never smoked until the beginning of their 2nd year were enrolled in the study. A Cox proportional-hazards regression analysis was performed to reveal the association between lifestyle characteristics at the beginning of the 2nd year and the start of smoking during the 2nd and 3rd years.

RESULTS

A total of 12,872 participants were enrolled in the analyses, 865 of whom started smoking during the subsequent 2 years. Among the lifestyle characteristics we examined, skipping breakfast 2-4 times a week (hazard ratio [HR] = 1.6; 95% CI = 1.4-1.9) or ≥ 5 times a week (HR = 2.0; 95% CI = 1.6-2.5), eating out for supper 2-4 times a week (HR = 1.4; 95% CI = 1.2-1.7) or ≥ 5 times a week (HR = 1.4; 95% CI = 1.2-1.8), drinking occasionally (HR = 1.7; 95% CI = 1.5-2.0) or almost everyday (HR = 4.1; 95% CI = 3.1-5.7), and sleeping < 6 hr a day (HR = 1.3; 95% CI = 1.1-1.6) were significant risk factors for the start of smoking. However, exercising ≥ 5 times a week (HR = 0.5; 95% CI = 0.4-0.7) was a protective factor.

DISCUSSION

Our results suggested that even never-smoking undergraduates with poor life habits are likely to start smoking and would make good candidates for preventive intervention.