Leisure-Time, Occupational, and Commuting Physical Activity and Risk of Type 2 Diabetes in Japanese Workers: A Cohort Study

Toru Honda; Keisuke Kuwahara; Tohru Nakagawa; Shuichiro Yamamoto; Takeshi Hayashi; Tetsuya Mizoue

Disclosures

BMC Public Health. 2015;15(1004) 

In This Article

Results

In the present study, the participants who remained main analysis were less likely to include women (12.9 % vs. 22.5 %) and to have family history of diabetes (13.9 % vs. 17.4 %) and they had a lower HbA1c level compared with the excluded participants (n = 15,701). Included participants were more likely to engage in shift work (18.8 % vs. 13.3 %) and walk for commuting and worked longer hours (monthly overtime work of ≥45 h: 36.5 % vs. 26.6 %). Other variables including age, BMI, hypertension, smoking, alcohol use, sleep duration, occupational physical activity were not materially different between the excluded and included participants. Overall, the mean age of was 45.3 years (standard deviation: 8.4) and the BMI was 23.4 (standard deviation: 3.2) among the participants who remained analysis. Table 1 shows the characteristics of the participants according to the dose of leisure-time exercise. Compared with workers who engaged in a lower dose of leisure-time exercise, those who engaged in a higher dose of leisure-time exercise were older, had a higher BMI, tended to engage in sedentary work, and slept more, but were less likely to be a female, a shift worker or a smoker and walked less during commuting. Other factors, including alcohol use, having hypertension, and a family history of diabetes, were not materially different across the category of leisure-time exercise (P for trend >0.1).

During a mean follow-up of 5.2 years with 139,739 person-years, 1,770 workers developed type 2 diabetes. As shown in Table 2, there was a significant inverse association between the dose of leisure-time exercise and the risk of type 2 diabetes in the age- and sex-adjusted model. The HRs (95 % CIs) were 1.00 (reference), 0.83 (0.73, 0.95), 0.89 (0.76, 1.05), and 0.78 (0.65, 0.93) for increasing doses of leisure-time exercise (P for trend = 0.003). Further adjustment for other potential confounders, including physical activities during work and commuting as well as BMI, slightly attenuated the association (P for trend = 0.024). The corresponding HRs (95 % CIs) were 1.00 (reference), 0.87 (0.76, 1.00), 0.92 (0.78, 1.08), and 0.83 (0.69, 0.99).

Table 3 shows the HRs of incident cases of diabetes associated with exercise intensity according to the dose of leisure-time exercise. Vigorous-intensity exercise alone or vigorous-intensity exercise combined with moderate-intensity exercise yielded greater health benefits in terms of risk reduction for incident diabetes compared with moderate-intensity exercise alone at the same dose of activity. It should be noted that not all of the reductions were statistically significant. The sensitivity analysis showed similar results in which 3,457 workers with short follow-up terms (<3 years) were excluded (data not shown).

When we calculated the risk of diabetes associated the dose of moderate-intensity exercise, the multivariable-adjusted HRs (95 % CIs) were 1.00 (reference), 0.91 (0.80, 1.28), 1.08 (0.91, 1.28), and 0.90 (0.72, 1.13) with increasing dose of moderate-intensity exercise without BMI adjustment (Additional file 1: Table S1 http://www.biomedcentral.com/1471-2458/15/1004/additional). The corresponding risk of diabetes associated with the dose of vigorous-intensity exercise were 1.00 (reference), 0.67 (0.51, 0.88). 0.81 (0.58, 1.13), and 0.83 (0.62, 1.11) (P for trend = 0.063) with increasing dose of vigorous-intensity exercise as shown in Additional file 1: Table S1 http://www.biomedcentral.com/1471-2458/15/1004/additional.

Of 18 items of exercise during leisure, approximately 20 to 50 % risk reduction was observed for jogging, aerobics, tennis, soccer, and swimming, although most of the reductions did not reach statistical significance (Additional file 1: Table S2 http://www.biomedcentral.com/1471-2458/15/1004/additional).

Occupational physical activity and walking for commuting to and from work were not associated with risk of type 2 diabetes in any models (Table 4).

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