Editor's Note: Commentary based on Juraschek SP, Blaha MJ, Blumenthal RS, et al. Cardiorespiratory fitness and incident diabetes: the FIT (Henry Ford Exercise Testing) Project. Diabetes Care 2015;38:1075-81.

Background

Considerable evidence demonstrates the important role of cardiorespiratory fitness to prevent cardiovascular disease (CVD) risk factors, including type 2 diabetes mellitus (T2DM), and improve overall prognosis in many groups of patients. Although physical activity is the predominant mechanism to increase cardiorespiratory fitness, some of cardiorespiratory fitness may be genetically determined. Therefore, emphasis directed at improving cardiorespiratory fitness more so than increasing physical activity has been suggested.

Methods

Investigators studied a diverse sample of 47,000 individuals without T2DM (mean age 53 years; 48% women; 27% African American) at baseline from the Henry Ford Exercise Testing (FIT) Project to determine incident T2DM during a mean 5.2-year follow-up (2.6-8.3 years) on three consecutive encounters derived from electronic medical records or administrative claim files from a large health care system. Their analysis was performed with Cox proportional hazard models, which were adjusted for other potential T2DM risk factors.

Results

During follow-up, close to 7,000 patients (approximately 15%) developed T2DM. After adjusting for other T2DM risk factors, achieving ≥12 metabolic equivalents (METs) had a 54% lower risk of developing T2DM compared with those achieving <6 METs. The authors also found that each 1-MET increase was associated with an 8% lower risk of developing T2DM , and similar and consistent results were present across strata of age, gender, race, obesity, blood pressure, and lipids.

Conclusions

These data demonstrate that high levels of cardiorespiratory fitness are associated with considerably lower risk of T2DM.

Commentary/Perspective

These data from Juraschek et al. clearly demonstrate that higher levels of cardiorespiratory fitness are associated with considerably lower risk of T2DM in a very large cohort. This certainly suggests that greater efforts to increase cardiorespiratory fitness are needed to prevent the current T2DM epidemic. As the authors indicated, several prior studies, including several from the Aerobics Center Longitudinal Study from Steven Blair, PED and his colleagues,^1-4 have indicated a protective role of cardiorespiratory fitness in the development of T2DM. However, prior studies, including our own, were generally smaller and/or confined to more limited settings (single gender, Caucasian, or narrow age groups). On the other hand, this current study from the FIT Project demonstrated the importance of high cardiorespiratory fitness to protect against T2DM in one of the largest longitudinal studies and demonstrated that this was independent of many other major risk factors for T2DM. This study clearly demonstrated a very strong inverse linear association between cardiorespiratory fitness and T2DM risk, with a greater risk reduction in individuals with 10 METs or higher, realizing that gender and age also impact MET values. For example, women have approximately 2 METs lower cardiorespiratory fitness capacity than men, and cardiorespiratory fitness declines with age, and the rate of decline accelerates markedly with advancing age in healthy populations.⁵

Considerable evidence demonstrates the critical role of cardiorespiratory fitness to not only prevent T2DM and other major CVD risk factors but, particularly, to improve CVD – and all-cause mortality in patients with T2DM, CVD risk factors, and known CVD.^6,8 Therefore, greater efforts are needed to increase levels of physical activity and cardiorespiratory fitness throughout the health care system.^6,7,9

Although genetics may play a modest role in determining cardiorespiratory fitness, the major determinant of cardiorespiratory fitness by far is aerobic physical activity and exercise training.⁶ Although physical activity is important, cardiorespiratory fitness predicts the development of T2DM and subsequent prognosis considerably better than does physical activity levels.^6,7,8,10 Therefore, these results support recommendations for not only physical activity and exercise training in general, but also specifically physical activity/exercise training designed to provide effective increases in levels of cardiorespiratory fitness, which would go a long way to not only prevent T2DM but also major CVD events and mortality.^5-10

References

1. Wei M, Gibbons LW, Mitchell TL, et al. The association between cardiorespiratory fitness and impaired fasting glucose and type 2 diabetes mellitus in men. Ann Intern Med 1999;130:89-96.
2. Sui X, Hooker SP, Lee I-M, et al. A prospective study of cardiorespiratory fitness and risk of type 2 diabetes in women. Diabetes Care 2008;31:550-5.
3. Lee DC, Sui X, Church TS, Lee I-M, et al. Associations of cardiorespiratory fitness and obesity with risks of impaired fasting glucose and type 2 diabetes in men. Diabetes Care 2009;32:257-62.
4. Sieverdes JC, Sui X, Lee DC, et al. Physical activity, cardiorespiratory fitness and the incidence of type 2 diabetes in a prospective study of men. Br J Sports Med 2010;44:238-44.
5. Lee DC, Artero EG, Sui X, Blair SN. Mortality trends in the general population: the importance of cardiorespiratory fitness. J Psychopharmacol 2010;24:27-35.
6. Lavie CJ, Arena R, Swift DL, et al. Exercise and the cardiovascular system: clinical science and cardiovascular outcomes. Circ Res 2015;117:207-19.
7. Kaminsky LA, Arena R, Beckie TM, et al. The importance of cardiorespiratory fitness in the United States: the need for a national registry: a policy statement from the American Heart Association. Circulation 2013;127:652-62.
8. Lee DC, Sui X, Ortega FB, et al. Comparison of leisure-time physical activity and cardiorespiratory fitness as predictors of all-cause mortality in men and women. Br J Sports Med 2011;45:504-10.
9. Vuori IM, Lavie CJ, Blair SN. Physical activity promotion in the health care system. Mayo Clin Proc 2013;88:1446-61.
10. Myers J, McAuley P, Lavie CJ, et al. Physical activity and cardiorespiratory fitness as major markers of cardiovascular risk: their independent and interwoven importance to health status. Prog Cadiovasc Dis 2015;57:306-14.

Keywords: African Americans, Blood Pressure, Cardiovascular Diseases, Diabetes Mellitus, Type 2, Electronic Health Records, Exercise, Exercise Test, Follow-Up Studies, Lipids, Longitudinal Studies, Metabolic Equivalent, Obesity, Prognosis, Proportional Hazards Models, Research Personnel, Risk Factors, Risk Reduction Behavior

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