Stephen W. Farrell

Cardiorespiratory Fitness Levels Among US Adults 20–49 Years of Age: Findings From the 1999–2004 National Health and Nutrition Examination Survey

Data from the 1999-2004 National Health and Nutrition Examination Survey were used to describe the distribution of cardiorespiratory fitness and its association with obesity and leisure-time physical activity (LTPA) for adults 20-49 years of age without physical limitations or indications of cardiovascular disease. A sample of 7,437 adults aged 20-49 years were examined at a mobile examination center. Of 4,860 eligible for a submaximal treadmill test, 3,250 completed the test and were included in the analysis. The mean maximal oxygen uptake ( max) was estimated as 44.5, 42.8, and 42.2 mL/kg/minute for men 20-29, 30-39, and 40-49 years of age, respectively. For women, it was 36.5, 35.4, and 34.4 mL/kg/minute for the corresponding age groups. Non-Hispanic black women had lower fitness levels than did non-Hispanic white and Mexican-American women. Regardless of gender or race/ethnicity, people who were obese had a significantly lower estimated maximal oxygen uptake than did nonobese adults. Furthermore, a positive association between fitness level and LTPA participation was observed for both men and women. These results can be used to track future population assessments and to evaluate interventions. The differences in fitness status among population subgroups and by obesity status or LTPA can also be used to develop health policies and targeted educational campaigns.

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.

Cardiorespiratory Fitness, Different Measures of Adiposity, and Cancer Mortality in Men

Objective: The purpose was to examine the prospective relationship among cardiorespiratory fitness level (CRF), different measures of adiposity, and cancer mortality in men.

Cardiorespiratory fitness, adiposity, and all-cause mortality in women.

PURPOSE To determine the prospective associations among cardiorespiratory fitness (CRF), different measures of adiposity, and all-cause mortality in women. METHODS A total of 11,335 women completed a comprehensive baseline examination between 1970 and 2005. Clinical measures included body mass index (BMI), waist circumference (WC), waist-to-height ratio (W/HT), waist-to-hip ratio (W/Hip), percent body fat (%BF), and CRF quantified as duration of a maximal exercise test. Participants were classified by CRF as low (lowest 20%), moderate (middle 40%), and high (highest 40%) as well as by standard clinical cut points for adiposity measures. Hazard ratios (HR) were computed using Cox regression analysis. RESULTS During a mean follow-up of 12.3 ± 8.2 yr, 292 deaths occurred. HR for all-cause mortality were 1.0, 0.60, and 0.54 for low, moderate, and high fit groups, respectively (P for trend G0.01). Adjusted death rates of overweight/obese women within each adiposity exposure were somewhat higher compared with normal-weight women and approached statistical significance for BMI, %BF, and W/HT (P = 0.08, P = 0.08, and P = 0.07, respectively). When grouped for joint analyses into categories of fit and unfit (upper 80% and lower 20% of CRF distribution, respectively), HR were significantly higher in unfit women within each stratum of BMI compared with fit–normal BMI women. Fit women with high %BF (HR = 1.0), high WC (HR = 0.9), and high W/HT (HR = 1.2) had no greater risk of death compared with fit–normal-weight women (referent). CONCLUSIONS Low CRF in women was a significant independent predictor of all-cause mortality. Higher CRF was associated with lower mortality within each category of each adiposity exposure. Using adiposity measures as predictors of all-cause mortality in women may be misleading unless CRF is also considered.

Cardiorespiratory Fitness and Metabolic Risk

The present study sought to evaluate the relation between cardiovascular risk factors and cardiorespiratory fitness (CRF) in a large population. Low CRF has been associated with increased total mortality and cardiovascular mortality. The mechanisms underlying greater cardiovascular mortality have not yet been determined. A series of cardiovascular risk factors were measured in 59,820 men and 22,192 women who had undergone determinations of CRF with maximal exercise testing. The risk factor profiles were segregated into 5 quintiles of CRF. With decreasing CRF, increases occurred in obesity, triglycerides, non-high-density lipoprotein cholesterol, triglyceride/high-density lipoprotein ratios, blood pressure, metabolic syndrome, diabetes, and cigarette smoking. Self-reported physical activity declined with decreasing levels of CRF. In conclusion, it appears likely that the enrichment of cardiovascular risk factors, especially metabolic risk factors, account for a portion of the increased cardiovascular mortality in low-fitness subjects. The mechanisms responsible for this enrichment in subjects with a low CRF represent a challenge for future research.

Impact of Body Mass Index, Physical Activity, and Other Clinical Factors on Cardiorespiratory Fitness (from the Cooper Center Longitudinal Study)

Cardiorespiratory fitness (CRF) is widely accepted as an important reversible cardiovascular risk factor. In the present study, we examined the nonmodifiable and modifiable determinants of CRF within a large healthy Caucasian population of men and women. The study included 20,239 patients presenting to Cooper Clinic (Dallas, Texas) for a comprehensive medical examination from 2000 through 2010. CRF was determined by maximal treadmill exercise testing. Physical activity categories were 0 metabolic equivalent tasks (METs)/min/week (no self-reported moderate or vigorous intensity physical activity), 1 to 449 METs/min/week (not meeting physical activity guideline), 450 to 749 METs/min/week (meeting guideline), and ≥750 METs/min/week (exceeding guideline). Linear regression modeling was used to determine the most robust clinical factors associated with achieved treadmill time. Age, gender, body mass index (BMI), and physical activity were the most important factors associated with CRF, explaining 56% of the variance (R(2) = 0.56). The addition of all other factors combined (current smoking, systolic blood pressure, blood glucose, high-density and low-density lipoprotein cholesterol, health status) were associated with CRF (p <0.05) but additively only improved R(2) by 2%. There was a significant interaction between BMI and physical activity on CRF, such that normal-weight (BMI <25 kg/m(2)) subjects achieved higher CRF for a given level of physical activity compared to obese subjects (BMI ≥30 kg/m(2)). Percent body fat, not lean body mass, was the key factor driving this interaction. In conclusion, BMI was the most important clinical risk factor associated with CRF other than nonmodifiable risk factors age and gender. For a similar amount of physical activity, normal-weight subjects achieved a higher CRF level compared to obese subjects. These data suggest that obesity may offset the benefits of physical activity on achieved CRF, even in a healthy population of men and women.

Midlife Cardiorespiratory Fitness, Incident Cancer, and Survival After Cancer in Men: The Cooper Center Longitudinal Study

IMPORTANCE Cardiorespiratory fitness (CRF) as assessed by formalized incremental exercise testing is an independent predictor of numerous chronic diseases, but its association with incident cancer or survival following a diagnosis of cancer has received little attention. OBJECTIVE To assess the association between midlife CRF and incident cancer and survival following a cancer diagnosis. DESIGN, SETTING, AND PARTICIPANTS This was a prospective, observational cohort study conducted at a preventive medicine clinic. The study included 13 949 community-dwelling men who had a baseline fitness examination. All men completed a comprehensive medical examination, a cardiovascular risk factor assessment, and incremental treadmill exercise test to evaluate CRF. We used age- and sex-specific distribution of treadmill duration from the overall Cooper Center Longitudinal Study population to define fitness groups as those with low (lowest 20%), moderate (middle 40%), and high (upper 40%) CRF groups. The adjusted multivariable model included age, examination year, body mass index, smoking, total cholesterol level, systolic blood pressure, diabetes mellitus, and fasting glucose level. Cardiorespiratory fitness levels were assessed between 1971 and 2009, and incident lung, prostate, and colorectal cancer using Medicare Parts A and B claims data from 1999 to 2009; the analysis was conducted in 2014. MAIN OUTCOMES AND MEASURES The main outcomes were (1) incident prostate, lung, and colorectal cancer and (2) all-cause mortality and cause-specific mortality among men who developed cancer at Medicare age (≥65 years). RESULTS Compared with men with low CRF, the adjusted hazard ratios (HRs) for incident lung, colorectal, and prostate cancers among men with high CRF were 0.45 (95% CI, 0.29-0.68), 0.56 (95% CI, 0.36-0.87), and 1.22 (95% CI, 1.02-1.46), respectively. Among those diagnosed as having cancer at Medicare age, high CRF in midlife was associated with an adjusted 32% (HR, 0.68; 95% CI, 0.47-0.98) risk reduction in all cancer-related deaths and a 68% reduction in cardiovascular disease mortality following a cancer diagnosis (HR, 0.32; 95% CI, 0.16-0.64) compared with men with low CRF in midlife. CONCLUSIONS AND RELEVANCE There is an inverse association between midlife CRF and incident lung and colorectal cancer but not prostate cancer. High midlife CRF is associated with lower risk of cause-specific mortality in those diagnosed as having cancer at Medicare age.

Cardiorespiratory Fitness, Body Mass Index, and Heart Failure Mortality in Men: Cooper Center Longitudinal Study

Background—We evaluated the individual and joint associations among cardiorespiratory fitness (CRF), body mass index, and heart failure (HF) mortality, as well as the additive effect of an increasing number of cardiovascular risk factors on HF mortality in fit versus unfit men. Methods and Results—A total of 44 674 men without a history of cardiovascular disease underwent a baseline examination between 1971 and 2010. Measures included body mass index and CRF quantified as duration of maximal treadmill exercise testing. Participants were divided into age-specific low, moderate, and high CRF categories. Hazard ratios were computed with Cox regression analysis. During a mean follow-up of 19.8±10.4 years, 153 HF deaths occurred. Adjusted hazard ratios across high, moderate, and low CRF categories were 1.0, 1.63, and 3.97, respectively, whereas those of normal, overweight, and obese body mass index categories were 1.0, 1.56, and 3.71, respectively (P for trend <0.0001 for each). When grouped into categories of fit and unfit (upper 80% and lower 20% of CRF distribution, respectively), hazard ratios were significantly lower in fit compared with unfit men in normal and overweight body mass index strata (P<0.002) but not in obese men. Within men matched for the same number of HF risk factors, fit men had significantly lower HF mortality than unfit men (P⩽0.02). Conclusions—Higher baseline CRF is associated with lower HF mortality risk in men, regardless of the number of HF risk factors present. Men should be counseled on physical activity with the goal of achieving at least a moderate level of CRF, thereby presumably decreasing their risk of HF mortality.

Cardiorespiratory fitness, adiposity, and serum 25-dihydroxyvitamin D levels in women: the Cooper Center Longitudinal Study.

PURPOSE We examined the cross-sectional associations among cardiorespiratory fitness (CRF), different measures of adiposity, and serum vitamin D levels in women. METHODS Between 2007 and 2010, 1320 women completed a health examination. Measures included body mass index (BMI), waist circumference (WC), waist/hip ratio, percent body fat, CRF based on a maximal treadmill exercise test, and measurement of serum vitamin D. Participants were classified by CRF as unfit (lowest 20%) and fit (remaining 80%) based on age, as well as by clinical cutoff points for adiposity measures, and by categories of serum vitamin D. We examined trends of CRF and adiposity exposures across serum vitamin D categories. We calculated odds ratios (OR) of serum vitamin D insufficiency or deficiency across levels of adiposity exposures before and after adjustment for CRF. RESULTS We observed a significant positive trend for CRF across incremental serum vitamin D categories (p<0.001). When compared to ORs for normal weight women, ORs for serum vitamin D insufficiency or deficiency were significantly higher for overweight women within each adiposity exposure (p<0.05). When grouped into categories of fit and unfit (upper 80% and lower 20% of CRF distribution, respectively), serum vitamin D was significantly lower in unfit than in fit women within each stratum of WC and waist/hip ratio and within the normal weight BMI stratum. CONCLUSIONS Serum vitamin D levels are positively associated with CRF and negatively associated with different measures of adiposity in women. Higher CRF attenuates the relationship between adiposity level and serum vitamin D. Future prospective studies are warranted.

Cardiorespiratory Fitness, LDL Cholesterol, and CHD Mortality in Men

INTRODUCTION There are no published data regarding the joint association of cardiorespiratory fitness (CRF) and LDL cholesterol concentration with subsequent CHD mortality in men. METHODS A total of 40,718 healthy men received a comprehensive baseline clinical examination between 1971 and 2006. CRF was determined from a maximal treadmill exercise test. Participants were divided into categories of low (quintile 1), moderate (quintiles 2-3), and high (quintiles 4-5) CRF by age group, as well as by Adult Treatment Panel III-defined LDL categories. HRs for CHD mortality were computed with Cox regression analysis. RESULTS A total of 557 deaths due to CHD occurred during 16.7 ± 9.0 yr (681,731 man-years) of follow-up. After adjustment for age, examination year, smoking status, family history, and body mass index, a significant positive trend in CHD mortality was shown across decreasing categories of CRF. HRs with 95% confidence interval were 1.0 (referent), 1.18 (0.94-1.47), and 2.10 (1.65-2.67) for high, moderate, and low fit groups, P trend <0.0001. Adjusted HRs were significantly higher across increasing LDL categories: 1.0 (referent), 1.30 (0.87-1.95), 1.54 (1.04-2.28), 2.16 (1.45-3.21), and 2.02 (1.31-3.13), P trend <0.0001. When grouped by CRF category as well as by LDL category, there was a significant positive trend (P < 0.02) in adjusted mortality across decreasing categories of CRF within each LDL category. CONCLUSIONS CRF is strongly and inversely associated with CHD mortality in men. Compared with men with low CRF, at a moderate to high level of CRF, the risk of mortality within each LDL category is significantly attenuated. This study suggests that measurement of CRF should be considered for routine cardiovascular risk assessment and risk management.