Joint association of coffee consumption and other factors to the risk of type 2 diabetes: a prospective study in Finland

Objective: To examine joint associations of coffee consumption and other factors ( including physical activity, obesity and alcohol consumption) with the risk of type 2 diabetes. Design: Prospective follow-up study. Subjects: In all, 10188 Finnish men and 11197 women aged 35-74 years without a history of stroke, coronary heart disease or diabetes at baseline. Measurement: A self-administered questionnaire data on coffee, tea, alcohol and other food consumption, physical activity, smoking, socio-economic factors and medical history, together with measured height, weight and blood pressure using standardized protocol. Results: During a mean follow-up of 13.4 years, there were 964 incident cases of type 2 diabetes. Multivariate-adjusted (age, study year, systolic blood pressure, education, smoking, physical activity, body mass index (BMI) and fruit, vegetable, sausage, bread, alcohol and tea consumption) hazard ratio of type 2 diabetes in participants who drank 0-2, 3-6 and >= 7 cups of coffee were 1.00, 0.77 and 0.66 (P = 0.022 for trend) in men, 1.00, 0.71 and 0.52 (P = 0.001 for trend) in women, and 1.00, 0.75 and 0.61 (P < 0.001 for trend) in men and women combined (adjusted also for sex), respectively. This inverse association was consistent in subjects with any joint levels of physical activity and BMI, and in alcohol drinkers and non-drinkers. Among obese and inactive people, coffee drinking of seven cups or more daily reduced the risk of type 2 diabetes to half. Conclusions: Coffee drinking was associated with a reduced risk of type 2 diabetes in both men and women, and this association was observed regardless of the levels of physical activity, BMI and alcohol consumption.