Physical Fitness Among Swedish Military Conscripts and Long-Term Risk for Type 2 Diabetes Mellitus: A Cohort Study.

BACKGROUND

Early-life physical fitness has rarely been examined in relation to type 2 diabetes mellitus (DM) in adulthood because of the lengthy follow-up required. Elucidation of modifiable risk factors at young ages may help facilitate earlier and more effective interventions.

OBJECTIVE

To examine aerobic capacity and muscle strength at age 18 years in relation to risk for type 2 DM in adulthood.

DESIGN

National cohort study.

SETTING

Sweden.

PARTICIPANTS

1 534 425 military conscripts from 1969 to 1997 (97% to 98% of all men aged 18 years nationwide) without prior type 2 DM.

MEASUREMENTS

Aerobic capacity and muscle strength (measured in watts and newtons per kilogram of body weight, respectively) were examined in relation to type 2 DM identified from outpatient and inpatient diagnoses from 1987 to 2012 (maximum age, 62 years).

RESULTS

34 008 men were diagnosed with type 2 DM in 39.4 million person-years of follow-up. Low aerobic capacity and muscle strength were independently associated with increased risk for type 2 DM. The absolute difference in cumulative incidence of type 2 DM between the lowest and highest tertiles of both aerobic capacity and strength was 0.22% at 20 years of follow-up (95% CI, 0.20% to 0.25%), 0.76% at 30 years (CI, 0.71% to 0.81%), and 3.97% at 40 years (CI, 3.87% to 4.06%). Overall, the combination of low aerobic capacity and muscle strength was associated with a 3-fold risk for type 2 DM (adjusted hazard ratio, 3.07 [CI, 2.88 to 3.27]; P < 0.001), with a positive additive interaction (P < 0.001). These associations were seen even among men with normal body mass index.

LIMITATION

This cohort did not include women and did not measure physical fitness at older ages.

CONCLUSION

In this large cohort of Swedish male military conscripts, low aerobic capacity and muscle strength at age 18 years were associated with increased long-term risk for type 2 DM, even among those with normal body mass index.

PRIMARY FUNDING SOURCE

National Institutes of Health.