Poor Physical Fitness May Hike Type 2 Diabetes Risk Later in Life

After an 18-year study of more than 1.5 million Swedish soldiers, researchers have concluded that young men with poor physical fitness were more likely to develop type 2 diabetes later in life.

In results published in the Annals of Internal Medicine, Casey Crump, MD, PhD, of Icahn School of Medicine at Mount Sinai in New York, and colleagues determined that the combination of low aerobic capacity and poor muscle strength at age 18 was associated with a 3-fold increased risk later in life (adjusted hazard ratio [HR]=3.07; 95% CI, 2.8-3.27).

“We found that low aerobic capacity and muscle strength at age 18 years were independently associated with a higher risk for type 2 diabetes in adulthood among men with either normal or high BMI,” the researchers wrote. “These findings suggest that interventions to improve aerobic and muscle fitness levels early in life could help reduce risk for type 2 diabetes in adulthood.”

From 1969 to 1987, researchers enrolled more than 1.53 million 18-year-old Swedish military conscripts. At baseline, participants were evaluated for:

• Aerobic capacity*
• Muscle strength*
• BMI
• Height
• Weight
• Family history of diabetes
• Education
• Neighborhood socioeconomic status

Median age at the end of follow-up was 46.1 years and median age at diagnosis was 46.8 years. Mean follow-up was 25.7 years.

The absolute difference in cumulative incidence of type 2 diabetes 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%-0.25%), 0.76% at 30 years (95% CI, 0.71%- 0.81%), and 3.97% at 40 years (95% CI, 3.87%- 4.06%).

Low aerobic capacity was associated with significantly increased cumulative incidence of type 2 diabetes at 10, 20, 30, and 40 years of follow-up, regardless of strength level. Among men with low or medium aerobic capacity, low muscle strength was associated with increased cumulative incidence after 40 years of follow-up.

Men with both low aerobic capacity and muscle strength demonstrated the highest cumulative incidence of disease, up to 4.45% at 40 years. The risk difference relative to high aerobic capacity and muscle strength was 3.97% (95% CI, 3.87%-4.06%; P<.001).

In secondary analyses, researchers found an additive, but not multiplicative, connection between either low aerobic capacity or muscle strength and high BMI in relation to type 2 diabetes (P<.001). Data showed that even men with normal BMI who had low aerobic capacity and poor muscle strength were at increased risk for disease

In an accompanying editorial, Peter T. Katzmarzyk, PhD, chair of pediatric obesity and diabetes and associate executive director for population and public health sciences with Pennington Biomedical Research Center in Baton Rouge, Louisiana, wrote that the data show that fitness measures have significant inverse associations with the risk for type 2 diabetes in overweight and obese men, as well as in normal-weight men.

“These results indicate that enhancing physical fitness can potentially provide additional protection against type 2 diabetes at any body weight,” he said. “Given the global increase in type 2 diabetes prevalence, there is a pressing need for intervention strategies that reduce the progression of the disease as well as the risk for related complications and premature death.”

* per kilogram of body weight

References

1. Crump C, Sundquist J, Winkleby MA, Sieh W, Sundquist K. Physical Fitness Among Swedish Military Conscripts and Long-Term Risk for Type 2 Diabetes Mellitus: A Cohort Study. Ann Intern Med. 2016. doi:10.7326/M15-2002.
2. Katzmarzyk PT. Physical Fitness and Risk for Type 2 Diabetes Mellitus: Reducing Risk at Any Weight. Ann Intern Med. 2016. doi:10.7326/M16-0269.