articles
nature publishing group
See reviewer commentary page 1029
The Joint Effects of Cardiorespiratory Fitness and Adiposity on Mortality Risk in Men With Hypertension Paul A. McAuley1, Xuemei Sui2, Timothy S. Church3, James W. Hardin4, Jonathan N. Myers5 and Steven N. Blair2,4 Background Whether higher cardiorespiratory fitness (CRF) attenuates the mortality risk associated with higher adiposity in adults with hypertension (HTN) is poorly understood. Methods Participants were 13,155 men (mean age, 47.7 (s.d., 9.9) years) who completed a baseline health examination and maximal treadmill exercise test during 1974–2003. All men had HTN at baseline based on resting systolic blood pressure of ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg. CRF was quantified as the duration of a symptom-limited maximal treadmill exercise test, and was grouped for analysis as low (lowest 20%), moderate (middle 40%), and high (upper 40%). Distributions of body mass index (BMI), waist circumference (WC), and percent body fat (%BF) were grouped according to standard clinical guidelines.
Results During a mean follow-up of 12 years, 883 deaths (355 cardiovascular disease (CVD)) were recorded. Multivariate hazard ratios (HRs) (95% confidence interval) for all-cause mortality, using low-fitness as the reference group, were 0.58 (0.48–0.69) and 0.43 (0.35–0.54) for moderatefit and high-fit groups, respectively. We observed a similar pattern for CVD mortality. High-fit/obese men had no greater risk of all-cause (1.59 (0.95–2.67)) or CVD (1.23 (0.44–3.41)) death, high-fit/abdominal-obese men had no greater risk for all-cause (1.20 (0.80–1.78)) or CVD (0.62 (0.25–1.53)) death, and high-fit/percent body fat (%BF)-obese men had no greater risk for all-cause (1.19 (0.90–1.56)) or CVD (0.86 (0.52–1.43)) death compared with their high-fit/normal counterparts. Conclusions Fitness is a powerful effect modifier in the association of adiposity to mortality in men with HTN, negating the all-cause and CVD mortality risk associated with obesity. Am J Hypertens 2009; 22:1062-1069 © 2009 American Journal of Hypertension, Ltd.
Hypertension (HTN) is associated with increased all-cause and cardiovascular disease (CVD) mortality.1 Currently, nearly 30% of the US adult population is hypertensive.2 Higher levels of cardiorespiratory fitness (CRF)3–5 and physical activity6,7 can reduce the risk of HTN for healthy normotensive persons. Regular exercise can also lower resting blood pressure in hypertensive adults.8 However, the influence of fitness on all-cause and CVD mortality in people with HTN is not fully understood. Currently, over half of those with HTN are obese9 and the risk of HTN ranges from two10 to five times11 higher among 1Department of Human Performance and Sport Sciences, Winston-Salem State University, Winston-Salem, North Carolina, USA; 2Department of Exercise Science, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, USA; 3Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA; 4Department of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, USA; 5Department of Cardiology, Stanford University/ Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA. Correspondence: Paul A. McAuley (
[email protected])
Received 27 February 2009; first decision 12 April 2009; accepted 13 June 2009; advance online publication 16 July 2009 . doi:10.1038/ajh.2009.122 © 2009 American Journal of Hypertension, Ltd. 1062
obese individuals than among those of normal weight. Higher CRF reduces the mortality risks associated with both HTN12,13 and obesity.14–16 Few studies, however, have simultaneously examined the relation of fitness and adiposity to mortality in hypertensive persons and all of these studies assessed adiposity from body mass index (BMI).12,13,15 Although BMI is well correlated with %BF,17 at a given BMI there is considerable variation. For example, in subjects with a BMI of 25 kg/m2, body fat percentages can range from 20 to 50% (ref. 18). Therefore, other clinical measures of adiposity, such as %BF and waist circumference (WC), further elucidate associations among adiposity, fitness, and mortality in hypertensive persons. A previous report from our group provided compelling evidence that moderate to high levels of fitness can reduce all-cause mortality risk in hypertensive men.12 This report, however, did not examine the combined effects of fitness and adiposity on mortality. Such joint analyses may identify associations obscured in independent analyses alone. The purpose of this study was to examine the independent and joint effects of fitness and various clinical measures of adiposity (BMI, WC, and %BF) on all-cause and CVD mortality in men with HTN.
october 2009 | VOLUME 22 NUMBER 10 | 1062-1069 | AMERICAN JOURNAL OF HYPERTENSION
Fitness, Adiposity, and Mortality in Hypertension
Methods
Study population. The Aerobics Center Longitudinal Study is an ongoing, prospective epidemiologic study of patients examined at the Cooper Clinic in Dallas, Texas. Study participants came to the clinic for periodic preventive health examinations and for counseling regarding diet, exercise, and other lifestyle factors associated with increased risk of morbidity and mortality. Many participants were referred by their employers; others were referred by their physicians or were self-referred. Between 1974 and 2003, 35,151 men received a comprehensive medical examination and were enrolled in the study. Most participants are Caucasian and from middle and upper socioeconomic strata. The current analysis included participants who at baseline were free of self-report history of myocardial infarction or stroke, and cancer; had normal resting electrocardiograms, had complete data on all three adiposity measures, and were able to complete an exercise test to at least 85% of their agepredicted maximal heart rate. We excluded men with a BMI 102.0 cm); and %BF (normal
