Associations of cardiorespiratory fitness and parental history of diabetes with risk of type 2 diabetes

Abstract

Aims

We examined the independent and joint associations of cardiorespiratory fitness (CRF) and parental diabetes history on type 2 diabetes risk.

Methods

A cohort of 11,627 individuals aged 20–79 years was free of baseline diabetes, cardiovascular disease, and cancer. We measured CRF using a maximal treadmill exercise test, and parental diabetes by a medical history questionnaire.

Results

During an average 5.5 year follow-up, 572 cases of type 2 diabetes occurred. Compared with the least fit 20%, the multivariate hazard ratio (HR) (95% CI) was 0.59 (0.43–0.83) for the middle fit 40%, and 0.53 (0.38–0.75) for the high fit 40%. Those with parental diabetes had a 1.40-fold higher risk for developing type 2 diabetes. In combined analyses using fit, no parental diabetes as the referent, unfit with no parental diabetes was 1.79 (95% CI 1.25–2.57) times more likely to develop type 2 diabetes, while the risk with parental diabetes was 1.41 (95% CI 1.12–1.78) and 2.37 (95% CI 1.25–4.49) times higher in the fit and unfit, respectively.

Conclusions

While high CRF did not fully attenuate the risk of diabetes associated with parental diabetes, being fit reduces diabetes risk regardless of parental history.

Introduction

Type 2 diabetes is a major public health problem affecting approximately 7.8% of the U.S. population [1]. According to the American Diabetes Association, the total estimated cost of diabetes in 2007 in the U.S. was $174 billion [1]. The number of patients with type 2 diabetes is increasing rapidly, and it is projected that by 2025, there will be 380 million people with type 2 diabetes worldwide [2].

Two major risk factors for development of type 2 diabetes are low cardiorespiratory fitness (CRF) and family history of type 2 diabetes [3], [4], [5], [6], [7], [8]. These risk factors have been examined independently, however, there is limited research investigating the joint association of CRF and family diabetes history on risk of incident type 2 diabetes. As the number of individuals with type 2 diabetes increases, the proportion of individuals with family history of type 2 diabetes will also increase. It is therefore important to examine the joint association of CRF and family diabetes history to determine if CRF can attenuate the incident diabetes risk associated with family diabetes history.

Cardiorespiratory fitness, which can be objectively measured in a laboratory, provides quantitative data that is associated with physical activity. CRF is a stronger predictor of many health outcomes in comparison with self-reported physical activity [9]. Previous longitudinal studies have shown a strong inverse relationship between CRF and the incidence of type 2 diabetes [3], [4], [5], [6], [7] and randomized control trials have demonstrated that increased physical activity is accompanied by decreases in glucose and insulin, and a lower risk of developing type 2 diabetes [10], [11]. These data suggest that lifestyle modification may play a major role in the prevention of type 2 diabetes.

Type 2 diabetes is also known to have a strong genetic basis [8], and individuals with a family history of type 2 diabetes are more likely to have insulin resistance [12]. While family history is a non-modifiable risk factor, studies have demonstrated that CRF significantly reduces the risk of several health related outcomes, such as all-cause and cardiovascular disease mortality [13], [14], [15]. It is therefore worth exploring whether CRF can reduce the risk of incident diabetes in those with a family history of diabetes. The current study was designed to investigate the independent and joint associations of CRF and parental history of diabetes on the incidence of type 2 diabetes in men and women in the Aerobics Center Longitudinal Study (ACLS).