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The Relationship of Cardiorespiratory Fitness and Diabetes

Apr 3, 2015

Higher fitness may be linked to a lower risk of incident diabetes…

Many cross-sectional studies have observed a relationship between reduced cardiorespiratory fitness and glucose intolerance or diabetes risk. Other large cohort studies have also demonstrated that low fitness may precede the development of insulin resistance and diabetes. However, not much data has shown if demographic characteristics (age, sex, and race) or other diabetes-related risk factors such as (obesity, hypertension, and hyperlipidemia) alter the relationship between fitness and incident type diabetes.

Prior evidence has linked higher cardiorespiratory fitness with a lower risk of diabetes in ambulatory populations. Therefore, the objective of this study was to use a demographically diverse study sample, and examine the association of fitness with incident diabetes in 46,979 patients from The Henry Ford Exercise Testing (FIT) Project without diabetes at baseline.

In order to measure fitness, a clinician-referred treadmill stress test was performed between 1991 and 2009. Incident type diabetes was defined as a new diagnosis of diabetes ICD-9 codes on three separate consecutive encounters which were derived by utilizing electronic medical records or administrative claims files. Cardiorespiratory fitness, expressed in metabolic equivalents (METs), was based on the workload derived from the maximal speed and grade achieved during the total treadmill time. MET results were categorized into four groups based on the distribution of the data as follows: <6, 6–9, 10–11, and ≥12 METs. All other analyses were performed with Cox proportional hazards models and were adjusted for diabetes risk factors. P values < 0.05 were considered statistically significant.

Results observed show that study patients without diabetes (n = 46,979) had an average age of 52.5 years with 48% women and 27% black patients. Mean metabolic equivalents (METs) achieved was 9.5 (SD 3.0). The most common indications for stress testing were chest pain (52%), “rule out” ischemia (11%), and shortness of breath (9%). During a median follow-up period of 5.2 years (interquartile range 2.6–8.3 years), there were 6,851 new diabetes cases (14.6%). After adjustments were made, patients achieving ≥12 METs had a 54% lower risk of incident diabetes compared with patients achieving <6 METs (hazard ratio 0.46 [95% CI 0.41, 0.51]; P value trend of < 0.001). This relationship was preserved across strata of age, sex, race, obesity, hypertension, and hyperlipidemia.

In conclusion, the data collected did demonstrate that higher fitness is associated with a lower risk of incident type diabetes regardless of demographic characteristics and baseline risk factors.

Practice Pearls:

  • Greater fitness at a younger age was associated with the lowest risk of developing diabetes.
  • The author noted that results of this study may imply that there is greater benefit to being fit at a young age.
  • With regard to race, a lower risk of incident type diabetes was observed among the more fit white patients compared to the more fit black patients.

Stephen P. Juraschek, Michael J. Blaha, RogerS. Blumenthal, et al. “Cardiorespiratory Fitness and Incident Diabetes: The FIT (Henry Ford Exercise Testing) Project”. Diabetes Care. March 12, 2015.