Cardiorespiratory fitness and regular physical activity are inversely associated with the risk of hypertension, and exercise training has been shown to lower elevated blood pressure (BP). Genetic factors contribute significantly to the interindividual differences in endurance training-induced changes in BP. However, similar data on the genotype-by-fitness interactions on the risk of hypertension are scarce.
In 2000, we started a systematic collection of blood samples from all consenting subjects of the Aerobics Center Longitudinal Study (ACLS) with a goal to generate a resource for studies addressing genotype-by-fitness interaction effects on various health-related end points. Here, we introduce the rationale and design of the first study based on the ACLS genetics resource focusing on hypertension as the health outcome (HYPGENE study), and we report the associations of cardiorespiratory fitness and body mass index (BMI) with the risk of hypertension. All HYPGENE subjects (N = 1234) were healthy and normotensive at their first clinic visit. Cases (N = 629) developed hypertension during the follow-up period (mean 8.7 yr), whereas controls (N = 605) remained normotensive (mean follow-up 10.1 yr).
Cardiorespiratory fitness was the strongest predictor of the hypertension risk, with each maximal metabolic equivalent unit being associated with a 19% lower risk (95% confidence interval [95% CI], 12-24%). Each baseline BMI unit was associated with a 9% higher hypertension risk (95% CI, 4-13%). However, the association of BMI was greatly attenuated (odds ratio 1.04 [95% CI, 0.99-1.09]) when fitness also was included in the model.
The HYPGENE study will provide an excellent resource to address hypotheses regarding the genetic basis of hypertension while taking cardiorespiratory fitness level into account.
1Human Genomics Laboratory and 2Preventive Medicine Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA; 3Division of Biostatistics and Department of Psychiatry, Washington University School of Medicine, St. Louis, MO; 4Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, SC; and 5Cooper Institute, Dallas, TX
Address for correspondence: Tuomo Rankinen, Ph.D., Human Genomics Laboratory, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808; E-mail: email@example.com.
Submitted for publication January 2007.
Accepted for publication May 2007.