Breakfast skipping is positively associated with incidence of type 2 diabetes mellitus: Evidence from the Aichi Workers' Cohort Study

Background: Skipping breakfast has been suspected as a risk factor for type 2 diabetes (T2DM), but the associations are not entirely consistent across ethnicities or sexes, and the issue has not been adequately addressed in the Japanese population. Methods: We followed 4631 participants (3600 men and 1031 women) in a work-site cohort of participants aged 35-66 years in 2002 through 2011 for T2DM development. Frequency of eating breakfast was self-reported and was subsequently dichotomized to breakfast skippers, who eat breakfast 3-5 times/week or less, and to eaters. Cox proportional hazards models were used to adjust for potential confounding factors, including dietary factors, smoking and other lifestyles, body mass index (BMI), and fasting blood glucose (FBG) at baseline. Results: During 8.9 years of follow-up, 285 T2DM cases (231 men and 54 women) developed. Compared to participants who reported eating breakfast every day, maximally-adjusted hazard ratios and 95% confidence intervals (CI) of those with the frequency of almost every day and 3-5, 1-2, and 0 days/week were: 1.06 (95% CI, 0.73-1.53), 2.07 (95% CI, 1.20-3.56), 1.37 (95% CI, 0.82-2.29), and 2.12 (95% CI, 1.19-3.76), respectively. In a dichotomized analysis, breakfast skipping was positively associated with T2DM incidence (maximally-adjusted hazard ratio 1.73; 95% CI, 1.24-2.42). The positive associations were found in both men and women, current and non-current smokers, normal weight and overweight (BMI ≥25 kg/m2), and normal glycemic status and impaired fasting glycemic status (FBG 110 to <126 mg/dL) individuals at baseline (Ps for interaction all >0.05). Conclusions: The present study in middle-aged Japanese men and women suggests that skipping breakfast may increase the risk of T2DM independent of lifestyles and baseline levels of BMI and FBG.