Carolyn E. Barlow

Influences of cardiorespiratory fitness and other precursors on cardiovascular disease and all-cause mortality in men and women

OBJECTIVE To quantify the relation of cardiorespiratory fitness to cardiovascular disease (CVD) mortality and to all-cause mortality within strata of other personal characteristics that predispose to early mortality. DESIGN--Observational cohort study. We calculated CVD and all-cause death rates for low (least fit 20%), moderate (next 40%), and high (most fit 40%) fitness categories by strata of smoking habit, cholesterol level, blood pressure, and health status. SETTING Preventive medicine clinic. STUDY PARTICIPANTS Participants were 25341 men and 7080 women who completed preventive medical examinations, including a maximal exercise test. MAIN OUTCOME MEASURES Cardiovascular disease and all-cause mortality. RESULTS There were 601 deaths during 211996 man-years of follow-up, and 89 deaths during 52982 woman-years of follow-up. Independent predictors of mortality among men, with adjusted relative risks (RRs) and 95% confidence intervals (CIs), were low fitness (RR, 1.52;95% CI, 1.28-1.82), smoking (RR, 1.65; 95% CI, 1.39-1.97), abnormal electrocardiogram (RR, 1.64;95% CI, 1.34-2.01), chronic illness (RR, 1.63;95% CI, 1.37-1.95), increased cholesterol level (RR, 1.34; 95% CI, 1.13-1.59), and elevated systolic blood pressure (RR, 1.34; 95% CI, 1.13-1.59). The only statistically significant independent predictors of mortality in women were low fitness (RR, 2.10; 95% Cl, 1.36-3.21) and smoking (RR, 1.99; 95% Cl, 1.25-3.17). Inverse gradients were seen for mortality across fitness categories within strata of other mortality predictors for both sexes. Fit persons with any combination of smoking, elevated blood pressure, or elevated cholesterol level had lower adjusted death rates than low-fit persons with none of these characteristics. CONCLUSIONS Low fitness is an important precursor of mortality. The protective effect of fitness held for smokers and nonsmokers, those with and without elevated cholesterol levels or elevated blood pressure, and unhealthy and healthy persons. Moderate fitness seems to protect against the influence of these other predictors on mortality. Physicians should encourage sedentary patients to become physically active and thereby reduce the risk of premature mortality.

Cardiorespiratory Fitness Is Inversely Associated With the Incidence of Metabolic Syndrome A Prospective Study of Men and Women

Background—Few studies have reported the relationship between cardiorespiratory fitness and metabolic syndrome incidence, particularly in women. Methods and Results—We prospectively studied 9007 men (mean±SD age, 44±9 years; body mass index, 25±3 kg/m2) and 1491 women (age, 44±9 years; body mass index, 22±2 kg/m2) who were free of metabolic syndrome and for whom measures of waist girth, resting blood pressure, fasting lipids, and glucose were taken during baseline and follow-up examinations. Baseline cardiorespiratory fitness was quantified as duration of a maximal treadmill test. Metabolic syndrome was defined with NCEP ATP-III criteria. During a mean follow-up of 5.7 years, 1346 men and 56 women developed metabolic syndrome. Age-adjusted incidence rates were significantly lower (linear trend, P<0.001) across incremental thirds of fitness in men and women. After further adjustment for potential confounders, multivariable hazard ratios for incident metabolic syndrome among men in the low, middle, and upper thirds of fitness, were 1.0 (referent), 0.74 (95% CI, 0.65 to 0.84), and 0.47 (95% CI, 0.40 to 0.54) (linear trend P<0.001); in women, they were 1.0 (referent), 0.80 (95% CI, 0.44 to 1.46), and 0.37 (95% CI, 0.18 to 0.80) (linear trend P=0.01), respectively. Similar patterns of significant inverse associations between fitness and metabolic syndrome incidence were seen when men were stratified on categories of body mass index, age, and number of baseline metabolic risk factors, but patterns were variable in women. Conclusions—Low cardiorespiratory fitness is a strong and independent predictor of incident metabolic syndrome in women and men. Clinicians should consider the potential benefits of greater cardiorespiratory fitness in the primary prevention of metabolic syndrome, particularly among patients who have already begun to cluster metabolic syndrome components.

Associations Between Cardiorespiratory Fitness and C-Reactive Protein in Men

Objective—This study examined the association between cardiorespiratory fitness and C-reactive protein (CRP), with adjustment for weight and within weight categories. Methods and Results—We calculated median and adjusted geometric mean CRP levels, percentages of individuals with an elevated CRP (≥2.00 mg/L), and odds ratios of elevated CRP across 5 levels of cardiorespiratory fitness for 722 men. CRP values were adjusted for age, body mass index, vitamin use, statin medication use, aspirin use, the presence of inflammatory disease, cardiovascular disease, and diabetes, and smoking habit. We found an inverse association of CRP across fitness levels (P for trend<0.001), with the highest adjusted CRP value in the lowest fitness quintile (1.64 [1.27 to 2.11] mg/L) and the lowest adjusted CRP value in the highest fitness quintile (0.70 [0.60 to 0.80] mg/L). Similar results were found for the prevalence of elevated CRP across fitness quintiles. We used logistic regression to model the adjusted odds for elevated CRP and found that compared with the referent first quintile, the second (odds ratio [OR] 0.43, 95% CI 0.22 to 0.85), third (OR 0.33, 95% CI 0.17 to 0.65), fourth (OR 0.23, 95% CI 0.12 to 0.47), and fifth (OR 0.17, 95% CI 0.08 to 0.37) quintiles of fitness had significantly lower odds of elevated CRP. Similar results were found when examining the CRP-fitness relation within categories of body fatness (normal weight, overweight, and obese) and waist girth (<102 or ≥102 cm). Conclusions—Cardiorespiratory fitness levels were inversely associated with CRP values and the prevalence of elevated CRP values in this sample of men from the Aerobics Center Longitudinal Study.

Associations of muscle strength and fitness with metabolic syndrome in men

PURPOSE To examine the associations for muscular strength and cardiorespiratory fitness with the prevalence of metabolic syndrome among men. METHODS Participants were 8570 men (20-75 yr) for whom an age-specific muscular strength score was computed by combining the body weight adjusted one-repetition maximum measures for the leg press and the bench press. Cardiorespiratory fitness was quantified by age-specific maximal treadmill exercise test time. RESULTS Separate age and smoking adjusted logistic regression models revealed a graded inverse association for metabolic syndrome prevalence with muscular strength (beta = -0.37, P < 0.0001) and cardiorespiratory fitness (beta = -1.2, P < 0.0001). The association between strength and metabolic syndrome was attenuated (beta = -0.08, P < 0.01) when further adjusted for cardiorespiratory fitness. The association between cardiorespiratory fitness and metabolic syndrome was unchanged (beta = -1.2, P < 0.0001) after adjusting for strength. Muscular strength added to the protective effect of fitness among men with low (P trend = 0.0002) and moderate (P trend < 0.0001) fitness levels. Among normal weight (BMI < 25), overweight (BMI 25-30), and obese (BMI >or= 30) men, respectively, being strong and fit was associated with lower odds (73%, 69%, and 62% respectively, P < 0.0001) of having prevalent metabolic syndrome. CONCLUSIONS Muscular strength and cardiorespiratory fitness have independent and joint inverse associations with metabolic syndrome prevalence.

Physical activity, physical fitness, and all-cause and cancer mortality: A prospective study of men and women

We studied physical fitness and physical activity in relation to all-cause and cancer mortality in a cohort of 7080 women and 25,341 men examined at the Cooper Clinic in Dallas, Texas, during 1970 to 1989. Physical fitness was assessed at baseline by a maximal treadmill exercise test, while physical activity was self-reported on the attendant health habits questionnaire. Both men and women averaged about 43 years of age at baseline (range, 20 to 88 years), and they were followed for approximately 8 years on average. Through the end of 1989, the women contributed 52,982 person-years of observation and incurred 89 deaths, including 44 deaths due to cancer. The men contributed 211,996 person-years and incurred 601 deaths, with 179 due to cancer. After adjustment for baseline differences in age, examination year, cigarette habit, chronic illnesses, and electrocardiogram abnormalities, we found a strong inverse association between risk of all-cause mortality and level of physical fitness in both men and women (P for trend < 0.001). Physically active men also were at lower risk of all-cause mortality than were sedentary ones (P for trend = 0.01). Among women, however, self-reported physical activity was not significantly related to risk of death from all causes. The risk of mortality from cancer declined sharply across increasing levels of fitness among men (P for trend < 0.001), whereas among women the gradient was suggestive but not significant (P for trend = 0.07). Physically active men also were at lower risk of death from cancer than were sedentary men (P for trend = 0.002), but among women physical activity was unrelated to cancer mortality.

Influences of cardiorespiratory fitness levels and other predictors on cardiovascular disease mortality in men

PURPOSE This investigation quantifies the relation between cardiorespiratory fitness levels and cardiovascular disease (CVD) mortality within strata of other CVD predictors. METHODS Participants included 25,341 male Cooper Clinic patients who underwent a maximal graded exercise test. CVD death rates were determined for low (least fit one-fifth), moderate (next two-fifths), and high (top two-fifths) cardiorespiratory fitness categories by strata of smoking habit, blood cholesterol level, resting blood pressure, and health status. There were 226 cardiovascular deaths during 211,996 man-years of follow-up. RESULTS For individuals with none of the major CVD predictors (smoking, elevated resting systolic blood pressure, elevated blood cholesterol), there was a strong inverse relation (P = 0.001) between fitness level and CVD mortality. An inverse relation between CVD mortality and fitness level was seen within strata of cholesterol levels and health status. No evidence of a trend (P = 0.60) for decreased mortality was seen across fitness levels for individuals with elevated systolic blood pressure; however, a strong inverse gradient (P < 0.001) was seen across fitness levels for individuals with normal systolic blood pressure. There was a tendency for association between high levels of fitness and decreased CVD mortality in smokers compared with low and moderately fit smokers (P < 0.076). There was no significant association between level of fitness and CVD mortality for individuals with multiple (two or more) predictors (P = 0.325). Approximately 20% of the 226 CVD deaths in the population studied were attributed to low fitness level. CONCLUSIONS Moderate and high levels of cardiorespiratory fitness seem to provide some protection from CVD mortality, even in the presence of well established CVD predictors.

Usefulness of Cardiorespiratory Fitness as a Predictor of All-Cause and Cardiovascular Disease Mortality in Men With Systemic Hypertension

There is an inverse gradient of mortality across levels of cardiorespiratory fitness in healthy adults; however, the association of fitness to mortality in persons with comorbidities such as hypertension is not fully understood. This study quantifies the relation of cardiorespiratory fitness to all-cause mortality and cardiovascular disease (CVD) mortality in hypertensive men. In this observational cohort study, we calculated death rates for low, moderate, and high fitness categories in normotensive (n = 15,726) and hypertensive (n = 3,184) men, and in men without a history of hypertension but with elevated blood pressure (BP) (systolic BP > or = 140 or diastolic BP > or = 90 mm Hg) at baseline (n = 3,257). The participants were 22,167 men (average age 42.6 +/- 9.2 years [mean +/- SD]) who underwent a medical examination that included a maximal exercise test during 1970 to 1993, with mortality follow-up to December 31, 1994. We identified 628 deaths (188 from CVD) during 224,173 man-years of observation. There was an inverse linear trend across fitness groups for all-cause and CVD mortality. The relative risk (95% confidence interval [CI]), using the low fitness group as reference, for all-cause mortality in hypertensive men was 0.45 (95% CI 0.31 to 0.65) and 0.42 (95% CI 0.27 to 0.66) for moderate and high fitness groups, respectively, and in men with elevated BP, 0.49 (95% CI 0.34 to 0.70) and 0.44 (95% CI 0.29 to 0.68) for moderate and high fitness groups, respectively. The pattern of results was similar for CVD mortality. There was an inverse linear relation between fitness and death rate for all-cause mortality in both the uncontrolled and controlled hypertensive groups. This study provides evidence that moderate to high levels of cardiorespiratory fitness provide protection against all-cause and CVD mortality in hypertensive men and men without a history of hypertension but with elevated BP at examination.

Physical activity, physical fitness, and all-cause mortality in women: do women need to be active?

Physical inactivity is associated with higher mortality rates in most studies in men, but studies in women are more equivocal. The purpose of this study was to evaluate the relationship of sedentary living habits to all-cause mortality in women. A group of 3,120 adult women completed a preventive medical examination, and were followed for approximately 8 years for mortality. There were 43 deaths and a total of 25,433 person-years observed during follow-up. Physical fitness was assessed at baseline by a maximal exercise test on a treadmill, and physical activity was estimated by a self-administered questionnaire. Age-adjusted all-cause mortality rates were significantly inversely associated with physical fitness. Death rates were 40, 16, and 7 per 10,000 person-years of follow-up across low, moderate, and high categories of physical fitness, respectively. However, death rates did not differ across low, moderate, and high categories of physical activity. These findings are different than for men in the same study, where both physical activity and physical fitness were inversely associated with mortality risk. We attribute the lack of association between physical activity and mortality in women to be due to inadequate assessment of activity, and that this also is the likely explanation for the difference in results between women and men in published studies of physical activity and mortality.

Physical activity versus cardiorespiratory fitness: two (partly) distinct components of cardiovascular health?

Physical activity (PA) and cardiorespiratory fitness (CRF) both have inverse relationships to cardiovascular (CV) morbidity and mortality. Recent position papers and guidelines have identified the important role of both of these factors in CV health. The benefits of PA and CRF in the prevention of CV disease and risk factors are reviewed. In addition, assessment methodology and utilization in the research and clinical arenas are discussed. Finally, the benefits, methodology, and utilization are compared and contrasted to better understand the two (partly) distinct components and their impact on CV health.

Lifetime risks for cardiovascular disease mortality by cardiorespiratory fitness levels measured at ages 45, 55, and 65 years in men. The Cooper Center Longitudinal Study.

OBJECTIVES The purpose of this study was to determine the association between fitness and lifetime risk for cardiovascular disease (CVD). BACKGROUND Higher levels of traditional risk factors are associated with marked differences in lifetime risks for CVD. However, data are sparse regarding the association between fitness and the lifetime risk for CVD. METHODS We followed up 11,049 men who underwent clinical examination at the Cooper Institute in Dallas, Texas, before 1990 until the occurrence of CVD death, non-CVD death, or attainment of age 90 years (281,469 person-years of follow-up, median follow-up 25.3 years, 1,106 CVD deaths). Fitness was measured by the Balke protocol and categorized according to treadmill time into low, moderate, and high fitness, with further stratification by CVD risk factor burden. Lifetime risk for CVD death determined by the National Death Index was estimated for fitness levels measured at ages 45, 55, and 65 years, with non-CVD death as the competing event. RESULTS Differences in fitness levels (low fitness vs. high fitness) were associated with marked differences in the lifetime risks for CVD death at each index age: age 45 years, 13.7% versus 3.4%; age 55 years, 34.2% versus 15.3%; and age 65 years, 35.6% versus 17.1%. These associations were strongest among persons with CVD risk factors. CONCLUSIONS A single measurement of low fitness in mid-life was associated with higher lifetime risk for CVD death, particularly among persons with a high burden of CVD risk factors.