Joint Associations Of Cardiorespiratory Fitness And Body Mass Index With Mortality In Women

Abstract

The joint associations of low cardiorespiratory fitness (CRF) and body mass index (BMI) with mortality in women need further evaluation. PURPOSE To examine the associations among CRF, BMI, and other health indicators with all-cause and cardiovascular disease (CVD) mortality in adult women. METHODS Participants were 15,787 women (mean±SD: age 45±10 yrs; BMI 23±4, range 18.5–58.6 kg/m2) who had a medical examination between 1970 and 1998. CRF was quantified as the duration of a symptom-limited maximal treadmill exercise test. Women in the lowest fifth of the age-normalized distribution of exercise duration were classified as unfit; women in the upper four fifths of the distribution were classified as fit. BMI was computed from measured height and weight; women were grouped as normal weight (NW), overweight (OW) and obese (OB) according to NIH guidelines. Mortality surveillance was through December 31, 1998. RESULTS There were 418 deaths (101 CVD deaths) during an average follow-up of 12 years and 193,622 womanyears of exposure. The prevalence of NW, OW and OB was 80.5%, 14.6%, and 4.9% respectively. Age and exam year adjusted death rates (per 10,000 woman-yrs) in NW, OW, and OB women, respectively, were 22.0, 18.7, and 28.4 for all-cause mortality (P=0.78) and were 5.4, 3.3, and 9.6 for CVD mortality (P=0.25). Death rates in fit and unfit women were 20.5 and 31.1 for all-cause mortality (P<0.001) and were 4.8 and 8.1 for CVD mortality (P=0.03). Rates of all-cause and CVD mortality were lower in fit than unfit women in each stratum of BMI. A consistent pattern of higher all-cause mortality risk was seen in unfit women in each BMI stratum, however mortality risk was not consistently higher in the presence of conventional health indicators such as dyslipidemia, hypertension, and abnormal fasting glucose. CONCLUSIONS Overweight and OB were not associated with higher mortality risk; but low CRF was a significant mortality predictor in women. Low fitness was a more consistent predictor of higher mortality risk than conventional risk factors in each BMI-defined weight category. Supported by NIH Grant AG06945 and HL62508