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The effects of smoking on the 8-year (1984-1992) incidence of non-insulin-dependent diabetes mellitus (NIDDM) were investigated in a cohort of 2,312 male employees of an electrical company in Japan. The incidence rate was 2.2/1,000 person-years. After controlling for other known risk factors for NIDDM, a proportional hazards regression analysis indicated that those who were currently smoking 16-25 cigarettes per day had a 3.27 times higher risk of developing NIDDM during the follow-up period than never smokers (p or = 26 cigarettes per day. Among ever smokers, proportional hazards regression analysis also indicated that younger age at starting smoking was associated with an increased risk of NIDDM (p for trend = 0.09). These findings suggest that number of cigarettes smoked per day is important in the relation between smoking and NIDDM incidence, although the risks did not increase above a given amount of smoking. Starting smoking at a younger age also might be independently associated with an increased risk of NIDDM.
Kawakami et al. (Wed,) studied this question.