Fitness Trends in Young Adults and Incidence of Diabetes
What is the relationship between cardiorespiratory fitness (CRF) measured in young adulthood and middle age on development of prediabetes, defined as impaired fasting glucose and/or impaired glucose tolerance, or diabetes by middle age?
The 4,373 CARDIA (Coronary Artery Risk Development in Young Adults) study participants free from prediabetes/diabetes at baseline (year 0 [Y0]: 1985-1986, age 18-30 years) underwent CRF assessment using treadmill duration (converted to metabolic equivalents [METs]) at Y0, Y7, and Y20 (age 38-50 years) and prediabetes/diabetes status was assessed at Y0, Y7, Y10, Y15, Y20, and Y25. Body mass index (BMI) was included as a time-varying covariate. The outcome was development of either prediabetes or diabetes after Y0. Components of the models included age, race, sex, field center, coronary risk factors, BMI, smoking, energy intake, alcohol intake, education, systolic blood pressure (BP), BP medication use, and lipid profile.
Compared with CARDIA participants who did not develop prediabetes or diabetes by Y25, the participants who developed prediabetes or diabetes by Y25 tended to be older, black race and male sex, were more likely to take BP medication and to smoke, have higher weight, BMI, waist circumference, systolic BP, low-density lipoprotein cholesterol, daily alcohol intake and caloric intake, and show a decline in treadmill duration over 20 years. Higher fitness was associated with lower risk for developing incident prediabetes/diabetes (difference of 1 MET: hazard ratio [HR], 0.998; 95% confidence interval [CI], 0.998, 0.999, p < 0.01), which persisted (difference of 1 MET: HR, 0.998; 95% CI, 0.998, 0.999; p < 0.01) when adjusting for covariates. Fitness was associated with lower risk for developing prediabetes/diabetes, when adjusting for BMI over this time period.
The findings emphasize the importance of fitness in reducing the health burden of prediabetes and diabetes.
Among the strengths of CARDIA was the balance of age, race, sex, and educational and socioeconomic levels. Maintaining or improving fitness over time from young to middle-aged adults is worth it. It takes about 8 months of 1000 kcal/week of aerobic exercise to improve CRF by 1 MET in sedentary obese/overweight men and women with a mean age of 51 years.
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