Type 2 diabetes is associated with loss of HDL endothelium protective functions

Aims/Hypothesis

One of the hallmarks of diabetes is impaired endothelial function. Previous studies showed that HDL can exert protective effects on endothelium stimulating NO production and protecting from inflammation and suggested that HDL in obese people with diabetes and dyslipidemia may have lower endothelial protective function. We aimed to investigate whether type 2 diabetes impairs HDL endothelium protective functions in people with otherwise normal lipid profile.

Methods

In a case-control study (n = 41 per group) nested in the Cooper Center Longitudinal Study we tested the ability of HDL to protect endothelium by stimulating endothelial nitric oxide synthase activity and suppressing NFκB-mediated inflammatory response in endothelial cells. In parallel we measured HDL protein composition, sphinogosine-1-phosphate and P-selectin.

Results

Despite similar levels of plasma HDL-C the HDL in individuals with type 2 diabetes lost almost 40% of its ability to stimulate eNOS activity (P<0.001) and 20% of its ability to suppress TNFα-dependent NFκB-mediated inflammatory response in endothelial cells (P<0.001) compared to non-T2D controls despite similar BMI and lipid profile (HDL-C, LDL-C, TC, TG). Significantly, the ability of HDL to stimulate eNOS activity was negatively associated with plasma levels of P-selectin, an established marker of endothelial dysfunction (r = −0.32, P<0.001). Furthermore, sphingosine-1-phosphate (S1P) levels were decreased in diabetic plasma (P = 0.017) and correlated with HDL-mediated eNOS activation.

Conclusions/Interpretations

Collectively, our data suggest that HDL in individuals with type 2 diabetes loses its ability to maintain proper endothelial function independent of HDL-C, perhaps due to loss of S1P, and may contribute to development of diabetic complications.

Cardiorespiratory Fitness, Coronary Artery Calcium, and Cardiovascular Disease Events in a Cohort of Generally Healthy Middle-Age Men: Results From the Cooper Center Longitudinal Study

BACKGROUND

A robust literature demonstrates that coronary artery calcification (CAC) and cardiorespiratory fitness (CRF) are independent predictors of cardiovascular disease (CVD) events. Much less is known about the joint associations of CRF and CAC with CVD risk. In the setting of high CAC, high versus low CRF has been associated with decreased CVD events. The goal of this study was to assess the effect of continuous levels of CRF on CVD risk in the setting of increasing CAC burden.

METHODS

We studied 8425 men without clinical CVD who underwent preventive medicine examinations that included an objective measurement of CRF and CAC between 1998 and 2007. There were 383 CVD events during an average follow-up of 8.4 years. Parametric proportional hazards regression models based on a Gompertz mortality rule were used to estimate total CVD incidence rates at 70 years of age as well as hazard ratios for the included covariates.

RESULTS

CVD events increased with increasing CAC and decreased with increasing CRF. Adjusting for CAC level (scores of 0, 1-99, 100-399, and ≥400), for each additional MET of fitness, there was an 11% lower risk for CVD events (hazard ratio, 0.89; 95% confidence interval, 0.84-0.94). When CAC and CRF were considered together, there was a strong association between continuous CRF and CVD incidence rates in all CAC groups.

CONCLUSIONS

In a large cohort of generally healthy men, there is an attenuation of CVD risk at all CAC levels with higher CRF.

Moderate to High Levels of Cardiorespiratory Fitness Attenuate the Effects of Triglyceride to High-Density Lipoprotein Cholesterol Ratio on Coronary Heart Disease Mortality in Men

OBJECTIVE

To examine the prospective relationships among cardiorespiratory fitness (CRF), fasting blood triglyceride to high density lipoprotein cholesterol ratio (TG:HDL-C), and coronary heart disease (CHD) mortality in men.

METHODS

A total of 40,269 men received a comprehensive baseline clinical examination between January 1, 1978, and December 31, 2010. Their CRF was determined from a maximal treadmill exercise test. Participants were divided into CRF categories of low, moderate, and high fit by age group and by TG:HDL-C quartiles. Hazard ratios for CHD mortality were computed using Cox regression analysis.

RESULTS

A total of 556 deaths due to CHD occurred during a mean ± SD of 16.6±9.7 years (669,678 man-years) of follow-up. A significant positive trend in adjusted CHD mortality was shown across decreasing CRF categories (P for trend<.01). Adjusted hazard ratios were significantly higher across increasing TG:HDL-C quartiles as well (P for trend<.01). When grouped by CRF category and TG:HDL-C quartile, there was a significant positive trend (P=.04) in CHD mortality across decreasing CRF categories in each TG:HDL-C quartile.

CONCLUSION

Both CRF and TG:HDL-C are significantly associated with CHD mortality in men. The risk of CHD mortality in each TG:HDL-C quartile was significantly attenuated in men with moderate to high CRF compared with men with low CRF. These results suggest that assessment of CRF and TG:HDL-C should be included for routine CHD mortality risk assessment and risk management.

Lifelong Physical Activity Regardless of Dose Is Not Associated With Myocardial Fibrosis

BACKGROUND

Recent reports have suggested that long-term, intensive physical training may be associated with adverse cardiovascular effects, including the development of myocardial fibrosis. However, the dose-response association of different levels of lifelong physical activity on myocardial fibrosis has not been evaluated.

METHODS AND RESULTS

Seniors free of major chronic illnesses were recruited from predefined populations based on the consistent documentation of stable physical activity over >25 years and were classified into 4 groups by the number of sessions/week of aerobic activities ≥30 minutes: sedentary (group 1), <2 sessions; casual (group 2), 2 to 3 sessions; committed (group 3), 4 to 5 sessions; and Masters athletes (group 4), 6 to 7 sessions plus regular competitions. All subjects underwent cardiopulmonary exercise testing and cardiac magnetic resonance imaging, including late gadolinium enhancement assessment of fibrosis. Ninety-two subjects (mean age 69 years, 27% women) were enrolled. No significant differences in age or sex were seen between groups. Median peak oxygen uptake was 25, 26, 32, and 40 mL/kg/min for groups 1, 2, 3, and 4, respectively. Cardiac magnetic resonance imaging demonstrated increasing left ventricular end-diastolic volumes, end-systolic volumes, stroke volumes, and masses with increasing doses of lifelong physical activity. One subject in group 2 had late gadolinium enhancement in a noncoronary distribution, and no subjects in groups 3 and 4 had evidence of late gadolinium enhancement.

CONCLUSIONS

A lifelong history of consistent physical activity, regardless of dose ranging from sedentary to competitive marathon running, was not associated with the development of focal myocardial fibrosis.

Abstract 557: Type 2 Diabetes is Associated With Impaired High-Density Lipoprotein Endothelial Protective Function

Aim: One of the hallmarks of diabetes is impaired endothelial function. High density lipoproteins (HDL) can exert protective effects on endothelium stimulating NO production and protecting from inflammation. Previous study suggested that HDL in obese people with diabetes and metabolic syndrome and markedly low HDL-C lost endothelial protective function. We aimed to test whether type 2 diabetes impairs HDL endothelium protective functions in people with otherwise normal lipid profile.

Methods: In a case-control study (n=40 per group) nested in the Cooper Center Longitudinal Study, we isolated HDL and measured its ability to stimulate activity of endothelial nitric oxide synthase (eNOS; phosphorylation of Ser1177) in endothelial cells and the ability of HDL to suppress inflammatory response of endothelial cells (NFkB activation). Additionally, we also measured by LCMS levels of sphingosine-1-phosphate (S1P) and plasma P-selectin by ELISA.

Results: The HDL in people with type 2 diabetes lost almost 40% of its ability to stimulate eNOS activity (P<0.001) and 20% of its ability to suppress inflammation in endothelial cells ( P <0.001) compared to non-diabetic controls despite similar BMI and lipid profile (HDL-C, LDL-C, TC, TG).The ability of HDL to stimulate eNOS activity was negatively associated with plasma levels of P-selectin, an established marker of endothelial dysfunction (r=–0.32, P <0.001). Furthermore, sphingosine-1-phosphate (S1P) levels were decreased in plasma of people with diabetes ( P =0.017) and correlated strongly with HDL-mediated eNOS activation.

Conclusions: Collectively, our data suggest that HDL in individuals with type 2 diabetes loses its ability to maintain proper endothelial function independent of HDL-C, perhaps due to loss of S1P, and may contribute to development of diabetic complications.

Association Between Sitting Time and Cardiometabolic Risk Factors After Adjustment for Cardiorespiratory Fitness, Cooper Center Longitudinal Study, 2010-2013

Introduction

Objective estimates, based on waist-worn accelerometers, indicate that adults spend over half their day (55%) in sedentary behaviors. Our study examined the association between sitting time and cardiometabolic risk factors after adjustment for cardiorespiratory fitness (CRF).

Methods

A cross-sectional analysis was conducted with 4,486 men and 1,845 women who reported daily estimated sitting time, had measures for adiposity, blood lipids, glucose, and blood pressure, and underwent maximal stress testing. We used a modeling strategy using logistic regression analysis to assess CRF as a potential effect modifier and to control for potential confounding effects of CRF.

Results

Men who sat almost all of the time (about 100%) were more likely to be obese whether defined by waist girth (OR, 2.61; 95% CI, 1.25–5.47) or percentage of body fat (OR, 3.33; 95% CI, 1.35–8.20) than were men who sat almost none of the time (about 0%). Sitting time was not significantly associated with other cardiometabolic risk factors after adjustment for CRF level. For women, no significant associations between sitting time and cardiometabolic risk factors were observed after adjustment for CRF and other covariates.

Conclusion

As health professionals struggle to find ways to combat obesity and its health effects, reducing sitting time can be an initial step in a total physical activity plan that includes strategies to reduce sedentary time through increases in physical activity among men. In addition, further research is needed to elucidate the relationships between sitting time and CRF for women as well as the underlying mechanisms involved in these relationships.

Cardiorespiratory Fitness and Highly Sensitive Cardiac Troponin Levels in a Preventive Medicine Cohort

BACKGROUND

Cardiorespiratory fitness (CRF) and highly sensitive cardiac troponin T (hs-cTnT) are associated with risk of all-cause and cardiovascular mortality as well as incident heart failure. A link of low CRF to subclinical cardiac injury may explain this association. We hypothesized that CRF would be inversely associated with hs-cTnT measured in healthy adults over age 50.

METHODS AND RESULTS

We evaluated 2498 participants (24.7% female, mean age 58.7 years) from the Cooper Center Longitudinal Study between August 2008 and January 2012. Plasma specimens obtained shortly before CRF estimates by Balke treadmill testing were used for hs-cTnT assays. CRF was grouped into low CRF (category 1), moderate CRF (categories 2-3), and high CRF (categories 4-5). Multivariable logistic regression was used to estimate the association of CRF with hs-cTnT. The prevalence of measurable hs-cTnT (≥3 ng/L) was 78.5%. In multivariable analyses, low-fit individuals were significantly more likely than high-fit individuals to have elevated hs-cTnT (≥14 ng/L) (odds ratio 2.47, 95% CI 1.10-5.36).

CONCLUSIONS

In healthy older adults, CRF is inversely associated with hs-cTnT level adjusted for other risk factors. Prospective studies are needed to evaluate whether improving CRF is effective in preventing subclinical cardiac injury.

High Cardiorespiratory Fitness Is Associated with Reduced Risk of Low Bone Density in Postmenopausal Women

PURPOSE

The goal of this study was to determine the association between cardiorespiratory fitness (CRF) and bone mineral density (BMD) of the femoral neck (FN) in postmenopausal women using existing Cooper Center Longitudinal Study data.

MATERIALS AND METHODS

A cohort of 1,720 predominantly healthy Caucasian women (57.1 ± 6.9 years) underwent preventive medical examinations that included CRF assessment by maximal Balke treadmill testing and measurement of BMD by dual-energy X-ray absorptiometry. CRF was estimated from total treadmill time and categorized into five categories of CRF (further defined as fitness category 1 = low fitness, 2-3 = moderate fitness, and 4-5 = high fitness). Logistic regression was used to characterize the association between CRF and BMD, adjusting for age, weight, and resistance activity level.

RESULTS

Overall, the mean body-mass index (BMI) for all subjects was 25.0 ± 4.5 kg/m2, although BMI was in the obese range in the low fitness group. The prevalence of osteoporosis (T-score ≤ -2.5 at the FN) was greater in the low fit group than moderate or high fit (5.8% vs. 3.0% or 3.9%, respectively); with a similar pattern seen for prevalence of osteopenia (T-score > -2.5 and ≤ -1.0 at the FN) (47.5% vs. 46.4% or 44.8%, respectively). Higher age and lower weight were associated with low BMD. Fully adjusted logistic regression models showed an inverse association between CRF and low BMD of the FN. For T-score ≤ -1.0, the primary outcome, the odds ratio (OR) was 0.50 (95% confidence interval [CI] 0.32-0.79) for moderate fitness, and OR of 0.32 (95% CI 0.21-0.51) for high fitness was seen. For T-score ≤ -2.5 at the FN, OR was 0.30 (95% CI 0.11-0.80) for moderate fitness, and OR was 0.29 (95% CI 0.12-0.71) for high fitness.

CONCLUSION

Increased CRF levels are associated with reduced risk for low bone density in postmenopausal women.

The association between midlife cardiorespiratory fitness and later life chronic kidney disease: The Cooper Center Longitudinal Study

BACKGROUND

Chronic kidney disease (CKD) is a major public health problem, particularly in older age and in those with diabetes mellitus (DM), with high comorbidity and treatment costs.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

17,979 participants, 22% women with a mean age of 50.0 (SD 8.8), in the Cooper Center Longitudinal Study (CCLS) seen initially between 1971 to 2009 who also received Medicare coverage from 1999 to 2009.

PREDICTORS

Age, body mass index, blood pressure, cholesterol, glucose levels, current tobacco use, and cardiorespiratory fitness.

OUTCOMES

Incident CKD and DM were determined from Medicare administrative claims data.

RESULTS

During 116,973person-years of observation, 2022 cases of incident CKD occurred. Multivariable-adjusted proportional hazards models revealed a 24% lower risk of CKD among moderate fit (hazards ratio[HR] 0.76, 95% CI 0.67-0.85 compared to low fit) and a 34% lower risk of CKD among high fit (HR 0.66, 95% CI 0.58-0.76 compared to low fit). Even following the development of DM, fitness was associated with lower risk of CKD (HR 0.94, 95% CI 0.89-0.99) per 1-MET increment.

LIMITATIONS

Relatively homogeneous population of well-educated Caucasians.

CONCLUSION

Results of the present study suggest that higher fitness is associated with lower risk of CKD decades later even in at-risk populations such as diabetics. The findings support a role for enhancing fitness through regular physical activity in preventive strategies for CKD including those who may develop DM in later life.

Distinct Brain and Behavioral Benefits from Cognitive vs. Physical Training: A Randomized Trial in Aging Adults

Insidious declines in normal aging are well-established. Emerging evidence suggests that non-pharmacological interventions, specifically cognitive and physical training, may counter diminishing age-related cognitive and brain functions. This randomized trial compared effects of two training protocols: cognitive training (CT) vs. physical training (PT) on cognition and brain function in adults 56-75 years. Sedentary participants (N = 36) were randomized to either CT or PT group for 3 h/week over 12 weeks. They were assessed at baseline-, mid-, and post-training using neurocognitive, MRI, and physiological measures. The CT group improved on executive function whereas PT group's memory was enhanced. Uniquely deploying cerebral blood flow (CBF) and cerebral vascular reactivity (CVR) MRI, the CT cohort showed increased CBF within the prefrontal and middle/posterior cingulate cortex (PCC) without change to CVR compared to PT group. Improvements in complex abstraction were positively associated with increased resting CBF in dorsal anterior cingulate cortex (dACC). Exercisers with higher CBF in hippocampi bilaterally showed better immediate memory. The preliminary evidence indicates that increased cognitive and physical activity improves brain health in distinct ways. Reasoning training enhanced frontal networks shown to be integral to top-down cognitive control and brain resilience. Evidence of increased resting CBF without changes to CVR implicates increased neural health rather than improved vascular response. Exercise did not improve cerebrovascular response, although CBF increased in hippocampi of those with memory gains. Distinct benefits incentivize testing effectiveness of combined protocols to strengthen brain health.

The Relationship Between Cardiorespiratory Fitness and Bone Mineral Density in Men: A Cross-sectional Study

OBJECTIVE

To determine the relationship between estimated cardiorespiratory fitness (CRF) and femoral neck (FN) bone mineral density (BMD) in men.

PATIENTS AND METHODS

This cross-sectional study included 2569 men aged 50 to 90 years (mean, 63.5 years) who had at least 1 health examination at a preventive medicine clinic between January 27, 1998, and February 24, 2015. Maximal treadmill tests were conducted using the Balke protocol and were used to estimate CRF. We stratified patients into low, moderate, and high CRF categories. The FN BMD was measured by dual-energy x-ray absorptiometry. Odds ratios (ORs) for T-scores of -2.5 or less (osteoporosis) and -1.0 or less (low BMD) were calculated for categorical CRF and were adjusted for weight, age, and days per week of resistance activity.

RESULTS

The sample prevalence of osteoporosis in the FN was 4.1% and of low BMD was 49.4%. There was a significant inverse association between higher CRF category and osteoporosis measured at the FN (moderate vs low: OR=0.34; 95% CI, 0.16-0.74; high vs low: OR=0.19; 95% CI, 0.09-0.42) and low BMD (moderate vs low: OR=0.64; 95% CI, 0.43-0.96; high vs low: OR=0.43; 95% CI, 0.29-0.65).

CONCLUSION

In men, CRF is directly associated with BMD. These results suggest that moderate-to-high CRF levels attained through regular physical activity may attenuate age-related decline in BMD. Further studies are needed to determine whether this translates to a lower risk of osteoporotic fracture in more fit men.

Association between omega-3 fatty acids and serum prostate-specific antigen

We examined the association between omega-3 fatty acids (O3FAs) and prostate-specific antigen (PSA) in a cross-sectional analysis of 6219 men examined at the Cooper Clinic from 2009 to 2013. We assayed O3FAs from red blood cell membranes and measured PSA levels in study participants. Multiple logistic regression was used to examine the association between O3FAs and PSA. The mean age of study participants was 55.5 years (SD = 9.8) with a mean PSA level of 1.31 ng/mL (SD = 1.5). Unadjusted analyses indicated that there was a slight, direct association with PSA and each of the O3FAs tested. However, after adjusting for age and body mass index (BMI), the associations were reversed but nonsignificant [odds ratio (OR) for PSA > 4 ng/mL: total omega-3 OR = 0.98 per each 1% of total fatty acids, 95% confidence interval (CI) = 0.93-1.03; docosahexaenoic acid OR = 1.01, 95% CI = 0.92-1.11; omega-3 index OR = 0.99, 95% CI = 0.93-1.05). Similar results were obtained after age and BMI adjustment when the omega-3 index was divided into undesirable (0.01-3.99%), intermediate (4.0-7.99%), and desirable ranges ( ≥ 8.0%). Given that the study had >80% power to detect an odds ratio <0.9 or >1.1, we conclude that associations between O3FAs and PSA levels are either nonexistent or quite weak in the population that this healthy sample represents.

Association of Ideal Cardiovascular Health and Long-term Healthcare Costs

INTRODUCTION

The American Heart Association's (AHA's) 2020 Strategic Impact Goals introduced the concept of ideal cardiovascular (CV) health based on seven health factors and behaviors associated with lower CV disease (CVD) risk. The association between CV health and healthcare costs has not been reported; therefore, we evaluated the association between CV health profile and later-life healthcare costs.

METHODS

Cooper Center Longitudinal Study participants (N=4,906; mean age, 56 years) receiving Medicare coverage from 1999 to 2009 were included. CV health behaviors (diet, physical activity, BMI, smoking) and CV health factors (blood pressure, total cholesterol, blood glucose) were categorized as unfavorable (zero to two ideal components); intermediate (two to four); and favorable (five to seven). Healthcare costs were cumulated from Medicare claims data, adjusted for inflation. Associations between midlife CV health status and non-CVD and CVD-related costs were estimated using multivariable quantile regression. Analyses were conducted in 2013 and 2014.

RESULTS

Favorable CV health was prevalent in 14.8% of men and 30.1% of women, with <1% having ideal levels of all health metrics. After 31,945 person-years of Medicare follow-up, individuals with favorable CV health exhibited 24.9% (95% CI=11.7%, 36.0%) lower median annual non-CVD costs and 74.5% (57.5%, 84.7%) lower median CVD costs than those with unfavorable CV health. Annualized differences were greater for non-CVD costs than for CVD costs ($1,175 vs $566).

CONCLUSIONS

Having more ideal CV health components in middle age, as outlined by the AHA 2020 Goals, is associated with lower non-CVD and CVD healthcare costs in later life.

Standing, Obesity, and Metabolic Syndrome: Findings From the Cooper Center Longitudinal Study

OBJECTIVE

To examine the cross-sectional relationships between standing time, obesity, and metabolic syndrome alongside and independent of leisure-time physical activity (LTPA).

PARTICIPANTS AND METHODS

The primary study sample consisted of 7075 adult patients (aged 20-79 years) from Cooper Clinic (Dallas, Texas). In this cross-sectional study we assessed the associations between reported standing time and directly measured obesity (body mass index ≥ 30), elevated waist circumference (men: ≥ 102 cm; women: ≥ 88 cm), body fat percentage (men: ≥ 25%; women ≥ 30%), and metabolic syndrome (yes/no). In addition, the joint associations of standing and LTPA on each outcome were examined. Multivariable logistic regression adjusting for confounders was used for statistical analyses.

RESULTS

Standing a quarter of the time or more was significantly associated with reduced odds of an elevated body fat percentage in men (P < .001) and a reduced likelihood of obesity (P < .009) and abdominal obesity (P=.04) in women. In addition, joint association analyses indicated that compared with the reference group (ie, not meeting the physical activity guidelines/standing almost none of the time), men and women who met the physical activity guidelines had lower odds of all obesity outcomes and metabolic syndrome with incremental additions of standing time (ie, a dose-response relationship).

CONCLUSION

Standing a quarter of the time per day or more is associated with reduced odds of obesity. The inverse relationship of standing to obesity and metabolic syndrome is more robust when combined with health-promoting LTPA. Prospective studies are warranted to confirm these findings and establish a causal relationship.

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.

Exercise outcomes in prevalent users of stimulant medications

BACKGROUND

To compare users of stimulant medications with matched nonusers on exercise outcomes during a maximal treadmill exercise test.

METHODS

A cross-sectional study of a community-based cohort comparing propensity-score-matched stimulant medication users (n = 245) and nonusers (n = 735) who underwent a maximal treadmill exercise test in the Cooper Center Longitudinal Study cohort from January 1, 1995 to December 31, 2013. Main Outcomes were peak systolic blood pressure (SBP), average rise in SBP, peak heart rate (HR), and estimated VO2max during exercise. A linear mixed model analysis was used to evaluate the effect of stimulant exposure on each of the exercise outcomes. In a sensitivity analysis, users were compared against nonusers for risk of chronotropic incompetence. Analyses were adjusted for relevant covariates and multiple testing.

RESULTS

Peak HR during exercise was significantly lower in stimulant medication users (least square mean estimate 170.2 beats/minute) compared to nonusers (174.4 beats/minute; p < 0.0001). Moreover, stimulant medication users had an increased risk of chronotropic incompetence compared to nonusers (adjusted odds ratio 3.28, 95% confidence interval 1.70 to 6.34, p = 0.0008). No significant differences were observed in the outcomes of peak SBP, average SBP rise, and estimated VO2max between matched groups.

CONCLUSIONS

Stimulant medication use was associated with a significant decrease in peak HR and an increased risk of chronotropic incompetence. Further investigation is required to understand the clinical significance of chronotropic incompetence in stimulant medication users. Concerns that stimulant medication use may increase peak SBP and average SBP during exercise were not supported by this study.

Effect of fitness on incident diabetes from statin use in primary prevention

OBJECTIVE

To assess the effect of cardiorespiratory fitness on the association between the initiation of statin therapy and incident diabetes.

PATIENTS AND METHODS

In a prospective observational study, we studied 6519 generally healthy men and 2334 women with two preventive health examinations from December 15, 1998 through December 18, 2013 which included measurement of fitness levels, statin therapy, risk factors for diabetes, and incident diabetes.

RESULTS

93 cases of incident diabetes occurred during an average follow-up of 3.0 years. After multivariable adjustment, an increased odds of incident diabetes with statin use was observed in those patients with impaired fasting glucose at baseline (odds ratio [OR]: 2.15, [95% CI:1.26 to 3.67]), but not among individuals with normal glucose levels (OR:1.85, [95% CI: 0.76 to 4.52]). Cardiorespiratory fitness attenuated but did not eliminate the increased risk of incident diabetes with statin use.

CONCLUSION

In a population of relatively healthy patients, statin use was not associated with incident diabetes in patients with normal fasting glucose at baseline. However, it was associated with incident diabetes in those patients with impaired fasting glucose at baseline, though this risk was substantially reduced by increasing fitness. In addition, increasing cardiorespiratory fitness was inversely associated with incident diabetes whether or not a patient was treated with a statin.