Seven-year changes in physical fitness, physical activity, and lipid profile in the CARDIA study. Coronary Artery Risk Development in Young Adults

Blood lipid markers are associated with hippocampal viscoelastic properties and memory in humans

Age-related memory loss shares similar risk factors as cardiometabolic diseases including elevated serum triglycerides (TGs) and low-density lipoprotein cholesterol (LDL-C) and reduced high-density lipoprotein cholesterol (HDL-C). The mechanisms linking these aberrant blood lipids to memory loss are not completely understood but may be partially mediated by reduced integrity of the hippocampus (HC), the primary brain structure for encoding and recalling memories. In this study, we tested the hypothesis that blood lipid markers are independently associated with memory performance and HC viscoelasticity-a noninvasive measure of brain tissue microstructural integrity assessed by high-resolution magnetic resonance elastography (MRE). Twenty-six individuals across the adult lifespan were recruited (14 M/12 F; mean age: 42 ± 15 y; age range: 22-78 y) and serum lipid profiles were related to episodic memory and HC viscoelasticity. All subjects were generally healthy without clinically abnormal blood lipids or memory loss. Episodic memory was negatively associated with the TG/HDL-C ratio. HC viscoelasticity was negatively associated with serum TGs and the TG/HDL-C ratio, independent of age and in the absence of associations with HC volume. These data, although cross-sectional, suggest that subtle differences in blood lipid profiles in healthy adults may contribute to a reduction in memory function and HC tissue integrity.

Walking in the Light: How History of Physical Activity, Sunlight, and Vitamin D Account for Body Fat-A UK Biobank Study

OBJECTIVE

The high prevalence of vitamin D deficiency and obesity drives the need for successful strategies that elevate vitamin D levels, prevent adipogenesis, and stimulate lipolysis. This study provides a theoretical model to evaluate how physical activity (PA) and sunlight exposure influence serum vitamin D levels and regional adiposity. This study hypothesized a posteriori that sunlight is associated with undifferentiated visceral adiposity by increasing the ratio of brown to white adipose tissue.

METHODS

Using 10-year longitudinal data, accelerometry, a sun-exposure questionnaire, and regional adiposity quantified by dual-energy x-ray absorptiometry imaging, a structural-equation mediation model of growth curves was constructed with a data-driven methodology.

RESULTS

Sunlight and PA conjointly increased serum vitamin D. Changes in vitamin D levels partially mediated how sunlight and PA impacted adiposity in visceral and subcutaneous regions within a subjective PA model. In an objective PA model, vitamin D was a mediator for subcutaneous regions only. Interestingly, sunlight was associated with less adiposity in subcutaneous regions but greater adiposity in visceral regions.

CONCLUSIONS

Sunlight and PA may increase vitamin D levels. For the first time, this study characterizes a positive association between sunlight and visceral adiposity. Further investigation and experimentation are necessary to clarify the physiological role of sunlight exposure on adipose tissue.

Effects of obesity on cholesterol metabolism and its implications for healthy ageing

The last few decades have witnessed a global rise in the number of older individuals. Despite this demographic shift, morbidity within this population group is high. Many factors influence healthspan; however, an obesity pandemic is emerging as a significant determinant of older people's health. It is well established that obesity adversely affects several metabolic systems. However, due to its close association with overall cardiometabolic health, the impact that obesity has on cholesterol metabolism needs to be recognised. The aim of the present review is to critically discuss the effects that obesity has on cholesterol metabolism and to reveal its significance for healthy ageing.

The association of religious affiliation with cholesterol levels among South Asians: the Mediators of Atherosclerosis in South Asians Living in America study

Background

South Asians have disproportionately high rates of cardiovascular disease. Dyslipidemia, a contributing factor, may be influenced by lifestyle, which can vary by religious beliefs. Little is known about South Asian religions and associations with dyslipidemia.

Methods

Cross-sectional analyses of the MASALA study (n = 889). We examined the associations between religious affiliation and cholesterol levels using multivariate linear regression models. We determined whether smoking, alcohol use, physical activity, and dietary pattern mediated these associations.

Results

Mean LDL was 112 ± 32 mg/dL, median HDL was 48 mg/dL (IQR:40–57), and median triglycerides was 118 mg/dL (IQR:88–157). Muslims had higher LDL and triglycerides, and lower HDL, while participants with no religious affiliation had lower LDL and higher HDL. The difference in HDL between Muslims and those with no religious affiliation was partly explained by alcohol consumption.

Conclusions

Religion-specific tailoring of interventions designed to promote healthy lifestyle to reduce cholesterol among South Asians may be useful.

Ten-Year Changes in Accelerometer-Based Physical Activity and Sedentary Time During Midlife: The CARDIA Study

We describe 10-year changes in accelerometer-determined physical activity (PA) and sedentary time in a midlife cohort of the Coronary Artery Risk Development in Young Adults Study, within and by race and sex groups. Participants (n = 962) wore the accelerometer with valid wear (≥4 of 7 days, ≥10 hours per day) at baseline (2005-2006; ages 38-50 years) and 10-year follow-up (2015-2016; ages 48-60 years). Data were calibrated to account for accelerometer model differences. Participants (mean age = 45.0 (standard deviation, 3.5) years at baseline) had reduced accelerometer counts overall (mean = -65.5 (standard error (SE), 10.2) counts per minute/day), and within race and sex groups (all P < 0.001). Sedentary time increased overall (mean = 37.9 (SE, 3.7) minutes/day) and within race and sex groups, whereas light-intensity PA (mean = -30.6 (SE, 2.7) minutes/day) and moderate- to vigorous-intensity PA (mean = -7.5 (SE, 0.8) minutes/day) declined overall and within race and sex groups (all P < 0.001). Significant differences in 10-year change estimates were noted by race and sex groups for accelerometer counts, sedentary time, and moderate- to vigorous-intensity PA bouts; black men had the greatest reductions in PA compared with other groups. PA declines during midlife were characterized by reductions in light-intensity PA with increases in sedentary time, which may have important health consequences. Targeted efforts are needed to preserve PA, regardless of intensity level, across midlife.

Exercise capacity and clinical outcomes in adults followed in the Cooperative Study of Sickle Cell Disease (CSSCD)

OBJECTIVES

To determine the factors associated with exercise capacity in adults with sickle cell disease (SCD) and its relationship to hospitalizations and mortality.

METHODS

A total of 223 participants in the Cooperative Study of Sickle Cell Disease (CSSCD) (64% female, 70% hemoglobin SS/Sβ⁰ thalassemia, mean age 43.3 ± 7.5 years) underwent maximal exercise testing using a treadmill protocol with a mean duration of 11.6 ± 5.2 minutes.

RESULTS

Female sex (β = -3.34, 95% CI [-1.80, -4.88], P < 0.001), older age (β = -0.14, 95% CI [-0.24, -0.04], P = 0.005), higher body mass index (β = -0.23, 95% CI [-0.37, -0.10]; P = 0.001), and lower hemoglobin (β = 0.56, 95% CI [0.08, 1.04], P = 0.02) were independently associated with lower fitness, while there was a trend with abnormal pulmonary function testing (β = -1.42, 95% CI [-2.92, 0.07]; P = 0.06). Lower percent-predicted forced expiratory volume in 1 second (FEV₁ ) was independently associated with lower fitness (β = 0.08, 95% CI [0.03, 0.13], P = 0.001). Genotype and hospitalization rates for pain and acute chest syndrome (ACS) prior to testing were not associated with exercise capacity. Baseline exercise capacity predicted neither future pain or ACS nor survival in our cohort. Adults with SCD tolerated maximal exercise testing.

CONCLUSIONS

Prospective studies are needed to further evaluate the impact of regular exercise and improved fitness on clinical outcomes and mortality in SCD.

The impact of changes in leisure time physical activity on changes in cardiovascular risk factors: results from The Finnmark 3 Study and SAMINOR 1, 1987-2003

Objective: The aim of this study was to examine the associations between changes in leisure time physical activity and changes in cardiovascular risk factors over 16 years and whether they differ between two ethnic groups in Norway.

Methods: Data were extracted from two population-based studies. Altogether, 3671 men and women participated in both surveys, and 30% reported being of Sami ethnicity. Leisure time physical activity was self-reported, and cardiovascular risk factors were measured. ANCOVA analysis was used to examine associations between changes in physical activity and changes in cardiovascular risk factors.

Results: After adjustment for age, sex, smoking, ethnicity and respective baseline values, favourable changes in body mass index (BMI) and levels of triglycerides were most pronounced in those who were active in both surveys (p < 0.05) whereas the opposite was the situation for cholesterol levels (p = 0.003). Changes in systolic blood pressure, diastolic blood pressure and resting heart rate were not significantly associated with change in physical activity. Ethnicity did not influence the associations between physical activity and cardiovascular risk factors.

Conclusion: Traditional cardiovascular risk factors were to a small extent associated with change in leisure time physical activity. Persistent physical activity was associated with beneficial changes in BMI and triglycerides.

The Hospital for Special Surgery Pediatric Functional Activity Brief Scale (HSS Pedi-FABS): Normative Data

BACKGROUND

Recent data have shown an increase in youth sports participation at younger ages, which may be linked to greater musculoskeletal injury risk. The Hospital for Special Surgery Pediatric Functional Activity Brief Scale (HSS Pedi-FABS) is a validated 8-item instrument designed to quantify the activity of children between 10 and 18 years old. Normative data on pediatric and adolescent activity level are unknown.

PURPOSE

To establish normative activity-level data for American youth and to determine if there is a natural decrease in activity level during adolescence.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A cross-sectional investigation was performed among 2002 US children and adolescents equally split by sex and age and representing census-weighted distributions of state of residency, race/ethnicity, and health insurance status. Respondents completed the HSS Pedi-FABS, as well as survey questions on demographics and sports participation. Normative data were reported with descriptive statistics. Linear regression analysis was performed to determine if there was an effect of age on activity level during adolescence.

RESULTS

A total of 2002 respondents completed the survey; the mean age of the respondents at the time of survey completion was 14.0 ± 2.6 years. Mean weekly amount of reported physical activity was 9.3 ± 8.4 hours. HSS Pedi-FABS scores were normally distributed with a mean of 15.4 ± 8.5 points (out of 30 possible points). There was a modest but statistically significant decrease in HSS Pedi-FABS activity scores with increasing age ( r = -0.175, P < .001), corresponding to a linear decrease in activity scores by 27% on average from age 10 to 18 years.

CONCLUSION

The current study provides baseline normative data for activity level in a census-weighted representative population sample of 2002 American youth through the use of a validated activity score (HSS Pedi-FABS). There was a modest but statistically significant decrease in activity scores with increasing age. These results will aid future research by providing normative, representative population-level activity data and will help to quantify the natural rate of decreased activity during adolescence.

The Influence of Life Events and Psychological Stress on Objectively Measured Physical Activity: A 12-Month Longitudinal Study

BACKGROUND

This study examined how life event occurrences and stressfulness influence objectively measured light through vigorous physical activity (PA) among young adults.

METHODS

Every 3 months over a 12-month period, 404 healthy young adults completed questionnaires on the occurrence and stress of 16 life events and wore an accelerometer for 10 days.

RESULTS

A modest positive relationship was seen between cumulative life event occurrences [between effect: β = 22.2 (9.7) min/d, P = .02] and cumulative stress [between effect: β = 7.6 (2.9) min/d, P = .01] with light through vigorous PA among men. When considering events individually, job change, starting a first job, beginning a mortgage, and changes in a relationship influenced men's PA. For women, mortgage, starting a first job, job change, and engagement had significant associations. Life event stressfulness influenced PA in women more than in men. For men, stress from changes in a relationship or job positively influenced PA. Stress of a mortgage, quitting a job, changing jobs or a first job influenced women's PA.

CONCLUSION

Considering each life event individually was more informative than the summation of life events or summation of stress. Specific life events substantially altered PA, and this change varied by gender, direction of association, and PA intensity and duration.

The Impact of Cardiorespiratory Fitness Levels on the Risk of Developing Atherogenic Dyslipidemia

BACKGROUND

Low cardiorespiratory fitness has been established as a risk factor for cardiovascular-related morbidity. However, research about the impact of fitness on lipid abnormalities, including atherogenic dyslipidemia, has produced mixed results. The purpose of this investigation is to examine the influence of baseline fitness and changes in fitness on the development of atherogenic dyslipidemia.

METHODS

All participants completed at least 3 comprehensive medical examinations performed by a physician that included a maximal treadmill test between 1976 and 2006 at the Cooper Clinic in Dallas, Texas. Atherogenic dyslipidemia was defined as a triad of lipid abnormalities: low high-density-lipoprotein cholesterol ([HDL-C] <40 mg/dL), high triglycerides ([TGs] ≥200 mg/dL), and high low-density-lipoprotein cholesterol ([LDL-C] ≥160 mg/dL).

RESULTS

A total of 193 participants developed atherogenic dyslipidemia during an average of 8.85 years of follow-up. High baseline fitness was protective against the development of atherogenic dyslipidemia in comparison with those with low fitness (odds ratio [OR] 0.57; 95% confidence interval [CI], 0.37-0.89); however, this relationship became nonsignificant after controlling for baseline HDL-C, LDL-C, and TG levels. Participants who maintained fitness over time had lower odds of developing atherogenic dyslipidemia than those with a reduction in fitness (OR 0.56; 95% CI, 0.34-0.91) after adjusting for baseline confounders and changes in known risk factors.

CONCLUSIONS

High fitness at baseline and maintenance of fitness over time are protective against the development of atherogenic dyslipidemia.

Does a family history of coronary heart disease modify the relationship between physical activity and blood pressure in young adults?

BACKGROUND

The purpose of this study was to examine the relationships between physical activity, a family history (FH) of coronary heart disease (CHD), and blood pressure (BP) in young adults. We were specifically interested in determining whether the relationship between moderate-to-vigorous physical activity and BP was modified by a FH of CHD.

METHODS

Subjects were 230 (103 males, 127 females) university students. Family history was self-reported and habitual physical activity was assessed with a 3-day activity diary. Indicators of habitual physical activity included estimated daily energy expenditure (EE) and EE in moderate-to-vigorous physical activity (MVPA) [median metabolic equivalent (MET) > or =4.8] and inactivity (IA) (MET<2.8). Blood pressure was measured by an automated device according to standard procedures.

RESULTS

A large proportion of the sample (63% of males and 68% of females) reported a FH of CHD. In general, correlations between physical activity and BP were low (r<0.30), but in the expected direction (i.e., positive for IA and negative for MVPA and EE). In males IA was significantly related to BP (r =0.25-0.29), but MVPA was not significantly related to BP (r= -0.01 to -0.16). In females diastolic BP was significantly related to IA (r= -0.21) and total EE (r= -0.18). Total EE was significantly correlated to DBP (r= -0.22) in males and to mean arterial pressure (r= -0.18) in females. No significant differences in BP were found between subjects with or without a FH of CHD. Slightly stronger correlations emerged between MVPA and BP for subjects with a negative FH of CHD compared to those with a positive FH of CHD.

CONCLUSION

These data show a significant association between sedentary behavior and blood pressure in young adults. It is suggestive that the magnitude of the relationship between MVPA and BP may be modified by a FH of CHD. Thus, individuals with a FH of CHD may not be as responsive to increased levels of MVPA compared to those without a FH of CHD.

Ready to be Physically Active? The Effects of a Course Preparing Low-Income Multiethnic Women to be more Physically Active

The purpose of this study is to evaluate the effect of a preintervention physical activity preparatory course on physical activity, and social, cognitive, and transtheoretical constructs. The sample included 82 low-income, multiethnic women (75% Latina) who completed an 8-week course designed to prepare them to become more active prior to randomization into a 10-month physical activity intervention. Participants completed precourse and postcourse measures. Paired-comparison t tests showed increases in knowledge, perceived social support for exercise, minutes of walking per week, and total cognitive and behavioral processes following the preparatory course. Perceived barriers and self-efficacy for exercise did not change from precourse to postcourse. Preintervention preparatory courses may be an effective way to increase social and cognitive constructs associated with physical activity behavior, potentially yielding a greater effect from subsequent interventions.

Association of Fitness With Incident Dyslipidemias Over 25 Years in the Coronary Artery Risk Development in Young Adults Study

INTRODUCTION

Few studies have examined the longitudinal associations of fitness or changes in fitness on the risk of developing dyslipidemias. This study examined the associations of (1) baseline fitness with 25-year dyslipidemia incidence and (2) 20-year fitness change on dyslipidemia development in middle age in the Coronary Artery Risk Development in Young Adults Study (CARDIA).

METHODS

Multivariable Cox proportional hazards regression models were used to test the association of baseline fitness (1985-1986) with dyslipidemia incidence over 25 years (2010-2011) in CARDIA (N=4,898). Modified Poisson regression models were used to examine the association of 20-year change in fitness with dyslipidemia incidence between Years 20 and 25 (n=2,487). Data were analyzed in June 2014 and February 2015.

RESULTS

In adjusted models, the risk of incident low high-density lipoprotein cholesterol (HDL-C); high triglycerides; and high low-density lipoprotein cholesterol (LDL-C) was significantly lower, by 9%, 16%, and 14%, respectively, for each 2.0-minute increase in baseline treadmill endurance. After additional adjustment for baseline trait level, the associations remained significant for incident high triglycerides and high LDL-C in the total population and for incident high triglycerides in both men and women. In race-stratified models, these associations appeared to be limited to whites. In adjusted models, change in fitness did not predict 5-year incidence of dyslipidemias, whereas baseline fitness significantly predicted 5-year incidence of high triglycerides.

CONCLUSIONS

Our findings demonstrate the importance of cardiorespiratory fitness in young adulthood as a risk factor for developing dyslipidemias, particularly high triglycerides, during the transition to middle age.

Physical activity patterns and risk of depression in young adulthood: a 20-year cohort study since childhood

PURPOSE

Little is known about how physical activity patterns during childhood and adolescence are associated with risk of subsequent depression. We examined prospective and retrospective associations between leisure physical activity patterns from childhood to adulthood and risk of clinical depression in young adulthood.

METHODS

Participants (759 males, 871 females) in a national survey, aged 9-15 years, were re-interviewed approximately 20 years later. Leisure physical activity was self-reported at baseline (1985) and follow-up (2004-2006). To bridge the interval between the two time-points, historical leisure activity from age 15 years to adulthood was self-reported retrospectively at follow-up. Physical activity was categorized into groups that, from a public health perspective, compared patterns that were least beneficial (persistently inactive) with those increasingly beneficial (decreasing, increasing and persistently active). Depression (major depressive or dysthymic disorder) was assessed using the Composite International Diagnostic Interview.

RESULTS

Compared with those persistently inactive, males who were increasingly and persistently active had a 69 and 65 % reduced risk of depression in adulthood, respectively (all p < 0.05). In retrospective analyses, females who were persistently active had a 51 % reduced risk of depression in adulthood (p = 0.01). Similar but non-significant trends were observed for leisure physical activity in females and historical leisure activity in males. Results excluded those with childhood onset of depression and were adjusted for various sociodemographic and health covariates.

CONCLUSIONS

Findings from both prospective and retrospective analyses indicate a beneficial effect of habitual discretionary physical activity since childhood on risk of depression in young adulthood.

PACES: a Physical Activity Campus Environmental Supports Audit on university campuses

PURPOSE

This study evaluated the policy and built and recreation environmental supports for physical activity on 13 university campuses.

DESIGN

Environmental audit survey.

SETTING

Thirteen U.S. universities, 2009. Subjects. University policies, recreation programs and facilities, and at least five additional buildings per campus.

MEASURES

The Physical Activity Campus Environmental Supports Audit was developed for this study.

ANALYSIS

Analysis of variance with post hoc Tukey's B and χ(2) assessed differences by institution and building type.

RESULTS

The mean obesogenic policy score was significantly lower than the desired score, ≥7 (p = .002), with only one campus scoring 10. The mean built environment audit score (5.4 ± 1.7) was low, with significant differences between institutions (p < .001) and only three campuses scoring above the desired score, ≥7. Although generally stairwells were clean and well lighted, there was a lack of signage to encourage stair use (p < .001). Overall, recreation programs (7.1 ± .7) and facilities (7.1 ± 1.2) scored well, but amenities scores were lower for satellite (2.8 ± 1.6) versus main (4.1 ± 1.8) recreation facilities (p = .04).

CONCLUSION

On these 13 university campuses, recreation programs and facilities were supportive of healthful lifestyles for obesity prevention, but policies and the built environment were not. This physical activity environmental audit survey requires testing in a wider sample of postsecondary institutions to corroborate its utility and provide evidence to support initiatives to improve campus environments for physical activity.

Eccentric endurance exercise economically improves metabolic and inflammatory risk factors

INTRODUCTION

Exercise is a cornerstone of cardiovascular prevention. Because many individuals are not willing or not able to perform regular exercise, new methods of exercise (like eccentric exercise) are necessary. Eccentric endurance exercise is supposed to be less strenuous than concentric exercise but its effects on glucose and lipid metabolism in relation to energy expenditure are unclear.

METHODS

We randomly allocated 45 healthy sedentary individuals to one of two groups, each hiking upwards or downwards for 2 months, with a crossover for a further 2 months; for the opposite way, a cable car was used. The difference in altitude was 540 metres; the distance was covered between three and five times a week. Energy expenditure was assessed for each hiking period.

RESULTS

Both eccentric and concentric endurance exercise improved glucose tolerance vs. baseline (by 4.1%, p = 0.136; 6.2%, p = 0.023, respectively). Of note, adjustment for energy expenditure per exercise unit (127 ± 22 kcal/unit with eccentric and 442 ± 78 kcal/unit with concentric exercise) revealed a significantly greater improvement of glucose tolerance per kilocalorie spent by eccentric than by concentric exercise (4-times more economical; 0.1123 mg h/dl/kcal vs. 0.0245 mg h/dl/kcal; p = 0.038). Also the decrease of low-density lipoprotein (LDL) cholesterol per kilocalorie spent was significantly stronger with eccentric exercise (0.0982 mg/dl/kcal vs. 0.0346 mg/dl/kcal, p = 0.014). Serum levels of C-reactive protein and creatine kinase activity were reduced in both groups.

CONCLUSION

Eccentric endurance exercise economically improves glucose tolerance and LDL cholesterol. It therefore is a promising new exercise modality for individuals who are not able to participate in more strenuous exercise regimens.

Financial strain and impaired fasting glucose: the moderating role of physical activity in the Coronary Artery Risk Development in Young Adults study

OBJECTIVES

Physical activity and financial strain are independent, and opposite, predictors of disease. This study examines whether physical activity modifies the concurrent and prospective relation between financial strain and impaired fasting glucose.

METHODS

Participants were part of the Coronary Artery Risk Development in Young Adults study, a prospective study examining the development of disease. Participants were recruited in 1985 to 1986 and followed up for 20 years. The outcome measures were fasting glucose (FG) levels at Years 7 and 20. FG was available at Years 7 and 20 from 3991 and 3500 participants, respectively.

RESULTS

The effects of financial strain on elevated glucose levels differed by physical activity levels as indicated by the significant interaction terms for the analyses of covariance at Year 7 (p = .02) and Year 20 (p = .04). Planned contrast comparisons demonstrated that FG levels in financially strained participants who were physically inactive were significantly different from financially strained participants who were active, and all participants with low financial strain. Specifically, in less active participants, the adjusted mean FG levels were higher in financially strained participants (2.27 mg/dL at Year 7 and 5.86 mg/dL at Year 20). In active participants, these differences were -1.78 mg/dL at Year 7 and negligible at Year 20.

CONCLUSIONS

In adults burdened by financial strain, physical activity is associated with a reduced risk of developing impaired FG up to 13 years later. This adds to a growing literature showing the potential of physical activity to moderate stress-related disease processes.

The triglyceride paradox in people of African descent

Even though insulin resistance, cardiovascular disease (CVD), and type 2 diabetes (T2D) are associated with hypertriglyceridemia, blacks with these conditions usually have normal triglyceride (TG) levels. This is often called a lipid paradox. More precisely, it is a "TG paradox." The pathways that lead to hypertriglyceridemia have been intensively explored. Yet, the pathways that allow TG levels to be normal in the presence of insulin resistance have received little attention and this is problematic. Tests designed for the early detection of insulin-resistant conditions often use elevated TG levels as a diagnostic criterion. However, insulin resistance, CVD, and T2D are not usually associated with hypertriglyceridemia in people of African descent; therefore, the widespread use of TG levels to predict these conditions needs re-evaluation. This review focuses on black-white differences in: (1) the lipid profile across North America, Europe, and Africa; (2) the efficacy of TG-based screening tests, specifically the metabolic syndrome and its two abbreviated versions, the hypertriglycerdemic waist and TG/high-density lipoprotein cholesterol (HDL-C) ratio; and (3) the mechanisms that allow TG to be normal even in the presence of insulin resistance. Overall, a broader understanding of how TG physiology varies by race could lead to better diagnostic tests and improved health outcomes.

Physical (in)activity over 20 y in adulthood: associations with adult lipid levels in the 1958 British birth cohort

OBJECTIVES

To investigate associations between physical (in)activity at different life-stages and lipids in mid-adulthood, examining the role of potential confounding and mediating factors, such as adiposity.

METHODS

Data from the 1958 British birth cohort (n=7824) were examined. Using linear regression, we analysed prospectively reported frequency of activity and TV-viewing (23, 33, 42 and 45 y) in relation to total, LDL-, HDL-cholesterol and triglycerides, at 45 y.

RESULTS

Activity at different ages was associated with HDL-cholesterol and triglycerides at 45 y: e.g. in men, a 1 day/week greater activity frequency at 42 y was associated with 0.006 mmol/L higher HDL-cholesterol and 1.4% lower triglycerides. Most associations attenuated, but were not entirely explained by adjustment for covariates (life-styles and socio-economic factors): e.g. among men, the estimated 2.0% lower triglycerides per 1 day/week greater frequency at 33 y reduced to 1.8% after adjustment. Among women, though not men, activity at both 23 and 45 y contributed cumulatively to HDL-cholesterol. For sedentary behaviour, associations were found for sitting at work: a 1 h/day greater sitting among men was associated with a 0.012 mmol/L lower HDL-cholesterol after adjustment for covariates. Associations were seen for TV-viewing: e.g. in men, a 0.04 mmol/L lower HDL-cholesterol and 5.9% higher triglycerides per hour/day greater TV-viewing at 45 y, attenuated, respectively, to 0.03 mmol/L and 4.6% after adjustment for covariates. Associations attenuated further after adjustment for current BMI. Associations for total and LDL-cholesterol were less consistent.

CONCLUSION

Activity and sedentary behaviour at different adult ages were associated with HDL-cholesterol and triglycerides in mid-adulthood. Associations were partly mediated by other life-style factors and by BMI.

Convergence of prevalence rates of diabetes and cardiometabolic risk factors in middle and low income groups in urban India: 10-year follow-up of the Chennai Urban Population Study

AIM

The aim of this study was to look for temporal changes in the prevalence of diabetes and cardiometabolic risk factors in two residential colonies in Chennai.

METHODS

Chennai Urban Population Study (CUPS) was carried out between 1996-1998 in Chennai in two residential colonies representing the middle income group (MIG) and lower income group (LIG), respectively. The MIG had twice the prevalence rate of diabetes as the LIG and higher prevalence rates of hypertension, obesity, and dyslipidemia. They were motivated to increase their physical activity, which led to the building of a park. The LIG was given standard lifestyle advice. Follow-up surveys of both colonies were performed after a period of 10 years.

RESULTS

In the MIG, the prevalence of diabetes increased from 12.4 to 15.4% (24% increase), while in the LIG, it increased from 6.5 to 15.3% (135% increase, p < .001). In the LIG, the prevalence rates of central obesity (baseline vs follow-up, male: 30.8 vs 50.9%, p < .001; female: 16.9 vs 49.8%, p < .001), hypertension (8.4 vs 20.1%, p < .001), hypercholesterolemia (14.2 vs. 20.4%, p < .05), and hypertriglyceridemia (8.0 vs 23.5%, p < .001) significantly increased and became similar to that seen in the MIG.

CONCLUSION

There is a rapid reversal of socioeconomic gradient for diabetes and cardiometabolic risk factors in urban India with a convergence of prevalence rates among people in the MIG and LIG. This could have a serious economic impact on poor people in developing countries such as India.

Changes in CVD risk factors in the activity counseling trial

Primary care facilities may be a natural setting for delivering interventions that focus on behaviors that improve cardiovascular disease (CVD) risk factors. The purpose of this study was to examine the 24-month effects of the Activity Counseling Trial (ACT) on CVD risk factors, to examine whether changes in CVD risk factors differed according to baseline risk factor status, and to examine whether changes in fitness were associated with changes in CVD risk factors. ACT was a 24-month multicenter randomized controlled trial to increase physical activity. Participants were 874 inactive men and women aged 35-74 years. Participants were randomly assigned to one of three arms that varied by level of counseling, intensity, and resource requirements. Because there were no significant differences in change over time between arms on any of the CVD risk factors examined, all arms were combined, and the effects of time, independent of arm, were examined separately for men and women. Time × Baseline risk factor status interactions examined whether changes in CVD risk factors differed according to baseline risk factor status. Significant improvements in total cholesterol, high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol, the ratio of total cholesterol to HDL-C, and triglycerides were seen in both men and women who had high (or low for HDL-C) baseline levels of risk factors, whereas significant improvements in diastolic blood pressure were seen only in those men with high baseline levels. There were no improvements in any risk factors among participants with normal baseline levels. Changes in fitness were associated with changes in a number of CVD risk factors. However, most relationships disappeared after controlling for changes in body weight. Improvements in lipids from the ACT interventions could reduce the risk of coronary heart disease in people with already high levels of lipids by 16%-26% in men and 11%-16% in women. Interventions that can be implemented in health care settings nationwide and result in meaningful population-wide changes in CVD risk factors are needed. The ACT physical activity interventions produced substantial improvements among men and women with elevated CVD risk factors.

Association of single-nucleotide polymorphisms from 17 candidate genes with baseline symptom-limited exercise test duration and decrease in duration over 20 years: the Coronary Artery Risk Development in Young Adults (CARDIA) fitness study

BACKGROUND

It is not known whether the genes involved with endurance performance during young adulthood are also involved with changes in performance. We examined the associations of gene variants with symptom-limited exercise test duration at baseline and decrease in duration over 20 years.

METHODS AND RESULTS

A total of 3783 (1835 black, 1948 white) and 2335 (1035 black, 1300 white) participants from the Coronary Artery Risk Development in Young Adults study were included in the baseline and 20-year models, respectively. Two hundred seventeen single-nucleotide polymorphisms (SNPs) in black participants and 171 in white participants from 17 genes were genotyped. In blacks, 5 SNPs in the ATP1A2, HIF1A, NOS3, and PPARGC1A loci tended to be associated (P<0.05) with baseline duration in a multivariate regression model. Blacks (n=99) with at least 4 of the most-favorable genotypes at these loci had an ≈2-minute longer baseline duration than those with only 2 such genotypes (P<0.0001). In whites, the HIF1A rs1957757 and PPARGC1A rs3774909 markers tended to be associated with baseline duration, but the association of a multimarker construct of the most-favorable genotypes at both SNPs with baseline duration was not statistically significant. In whites, 4 SNPs in the AGT, AMPD1, ANG, and PPARGC1A loci tended to be associated with decrease in exercise duration over 20 years, and those with all 4 favorable genotypes (n=40) had a 0.8-minute less decline in duration compared with those with none or 1 (n=232) (P<0.0001).

CONCLUSIONS

In multimarker constructs, alleles at genes related to skeletal muscle Na(+)/K(+) transport, hypoxia, and mitochondrial metabolism are associated with symptom-limited exercise test duration over time in adults.

Effect of a primary health-care-based controlled trial for cardiorespiratory fitness in refugee women

BACKGROUND

Refugee women have a high risk of coronary heart disease with low physical activity as one possible mediator. Furthermore, cultural and environmental barriers to increasing physical activity have been demonstrated. The aim of the study was to evaluate the combined effect of an approximate 6-month primary health care- and community-based exercise intervention versus an individual written prescription for exercise on objectively assessed cardiorespiratory fitness in low-active refugee women.

METHODS

A controlled clinical trial, named "Support for Increased Physical Activity", was executed among 243 refugee women recruited between November 2006 and April 2008 from two deprived geographic areas in southern Stockholm, Sweden. One geographic area provided the intervention group and the other area the control group. The control group was on a higher activity level at both baseline and follow-up, which was taken into consideration in the analysis by applying statistical models that accounted for this. Relative aerobic capacity and fitness level were assessed as the two main outcome measures.

RESULTS

The intervention group increased their relative aerobic capacity and the percentage with an acceptable fitness level (relative aerobic capacity > 23 O2 mlxkgxmin-1) to a greater extent than the control group between baseline and the 6-month follow-up, after adjusting for possible confounders (P = 0.020).

CONCLUSIONS

A combined primary health-care and community-based exercise programme (involving non-profit organizations) can be an effective strategy to increase cardiorespiratory fitness among low-active refugee women.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT00747942.

Do birth cohorts matter? Age-period-cohort analyses of the obesity epidemic in the United States

Many studies have cited the importance of secular changes or "period effects" as causes of the U.S. obesity epidemic. Unfortunately, relatively little attention has been devoted to the possible influence of cohort-related mechanisms. To address this current gap in the scientific literature, this investigation utilized the responses from 1.7 million participants in the 1976-2002 National Health Interview Surveys to determine how birth cohorts may have contributed to the rapid increase in the prevalence of obesity. Results from hierarchical age-period-cohort (HAPC) models confirmed that period effects are principally responsible for the U.S. obesity epidemic. However, HAPC models also demonstrated that birth cohort membership is influential. Independent of age and period effects, the predicted probability of obesity at age 25 increased by 30% for cohorts born between 1955 and 1975. Our results also showed that age, period and cohort effects varied by race/gender and educational attainment. For instance, increases in the predicted probabilities of obesity were particularly sharp for recent cohorts of Black females. Our investigation successfully demonstrated that both secular change and birth cohort membership have independently contributed to elevated odds of obesity among recent generations of Americans, suggesting that cohort-specific strategies may be needed to combat disconcertingly high rates of obesity in the U.S.

Association of 20-year changes in cardiorespiratory fitness with incident type 2 diabetes: the coronary artery risk development in young adults (CARDIA) fitness study

OBJECTIVE

To test the association of fitness changes over 7 and 20 years on the development of diabetes in middle age.

RESEARCH DESIGN AND METHODS

Fitness was determined based on the duration of a maximal graded exercise treadmill test (Balke protocol) at up to three examinations over 20 years from 3,989 black and white men and women from the Coronary Artery Risk Development in Young Adults study. Relative fitness change (percent) was calculated as the difference between baseline and follow-up treadmill duration/baseline treadmill duration. Diabetes was identified as fasting glucose >or=126 mg/dl, postload glucose >or=200 mg/dl, or use of diabetes medications.

RESULTS

Diabetes developed at a rate of 4 per 1,000 person-years in women (n = 149) and men (n = 122), and lower baseline fitness was associated with a higher incidence of diabetes in all race-sex groups (hazard ratios [HRs] from 1.8 to 2.3). On average, fitness declined 7.6% in women and 9.2% in men over 7 years. The likelihood of developing diabetes increased per SD decrease (19%) from the 7-year population mean change (-8.3%) in women (HR 1.22 [95% CI 1.09-1.39]) and men (1.45 [1.20-1.75]) after adjustment for age, race, smoking, family history of diabetes, baseline fitness, BMI, and fasting glucose. Participants who developed diabetes over 20 years experienced significantly larger declines in relative fitness over 20 years versus those who did not.

CONCLUSIONS

Low fitness is significantly associated with diabetes incidence and explained in large part by the relationship between fitness and BMI.

Population-based incidence of Type 2 diabetes and its associated risk factors: results from a six-year cohort study in Iran

Background

The Middle East is estimated to have the largest increase in prevalence of diabetes by 2030; yet there is lack of published data on the incidence of Type 2 diabetes in this region. This study aimed to estimate Type 2 diabetes incidence and its associated risk factors in an Iranian urban population.

Methods

Among 3307 non-diabetics ≥ 20 years (mean age 42 ± 13 years, 42% males), glucose tolerance test was performed at baseline in 1999–2001 and at two consecutive phases in 2001–2005 and 2005–2008. Diabetes and glucose tolerance status were defined according to the ADA 1997 criteria. Logistic regression was used to determine the independent variables associated with incident diabetes and their odds ratios (OR).

Results

After median follow-up of 6 years, 237 new cases of diabetes were ascertained corresponding to an age and sex standardized cumulative incidence of 6.4% (95%CI: 5.6–7.2) and incidence rate of 10.6 (9.2–12.1) per 1000 person years. Besides classical diabetes risk factors, female sex and low education level significantly increased risk of diabetes in age adjusted models. In full model, the independent predictors were age [OR, 95%CI: 1.2 (1.1–1.3)], family history of diabetes [1.8 (1.3–2.5)], body mass index ≥ 30 kg/m² [2.3 (1.5–3.6)], abdominal obesity [1.9 (1.4–2.6)], high triglyceride [1.4 (1.1–1.9)], Isolated impaired fasting glucose (IFG) [7.4 (3.6–15.0)], Isolated impaired glucose tolerance (IGT) [5.9 (4.2–8.4)] and combined IFG and IGT [42.2 (23.8–74.9)].

Conclusion

More than 1% of the Iranian urban population older than 20 years develops Type 2 diabetes each year. Combination of IFG and IGT was the strongest predictor of incident diabetes among the modifiable risk factors.

Longitudinal impact of physical activity on lipid profiles in middle-aged adults: the Atherosclerosis Risk in Communities Study

Evidence exists that increased levels of physical activity decrease the population burden of cardiovascular disease (CVD). Although risk factors for CVD, including plasma lipids and lipoproteins, have been associated with physical activity, studies including a sizeable number of minority participants are lacking. Our purpose was to interrogate the longitudinal effect of physical activity on plasma lipids and lipoproteins in the African American and white participants of the Atherosclerosis Risk in Communities (ARIC) Study. Nine years of follow-up data on 8,764 individuals aged 45-64 years at baseline were used in linear mixed-effects models to estimate the association between increases in baseline physical activity on mean change in HDL, LDL, total cholesterol, and triglyceride levels. Increases in the level of activity were associated with increases in HDL in all strata and decreases in triglycerides among white participants. Physical activity was associated with LDL in all women, while the association with total cholesterol was limited to African American women. This study is one of the few to investigate the effect of physical activity on lipids and lipoproteins in a race- and sex-specific manner. Overall our results highlight the importance of physical activity on plasma lipid profiles and provide evidence for novel differential associations.

Decline in physical fitness from childhood to adulthood associated with increased obesity and insulin resistance in adults

OBJECTIVE

To examine how fitness in both childhood and adulthood is associated with adult obesity and insulin resistance.

RESEARCH DESIGN AND METHODS

A prospective cohort study set in Australia in 2004-2006 followed up a cohort of 647 adults who had participated in the Australian Schools Health and Fitness Survey in 1985 and who had undergone anthropometry and cardiorespiratory fitness assessment during the survey. Outcome measures were insulin resistance and obesity, defined as a homeostasis model assessment index above the 75th sex-specific percentile and BMI >or=30 kg/m(2), respectively.

RESULTS

Lower levels of child cardiorespiratory fitness were associated with increased odds of adult obesity (adjusted odds ratio [OR] per unit decrease 3.0 [95% CI 1.6-5.6]) and insulin resistance (1.7 [1.1-2.6]). A decline in fitness level between childhood and adulthood was associated with increased obesity (4.5 [2.6-7.7]) and insulin resistance (2.1 [1.5-2.9]) per unit decline.

CONCLUSIONS

A decline in fitness from childhood to adulthood, and by inference a decline in physical activity, is associated with obesity and insulin resistance in adulthood. Programs aimed at maintaining high childhood physical activity levels into adulthood may have potential for reducing the burden of obesity and type 2 diabetes in adults.

Five-year change in physical activity is associated with changes in cardiovascular disease risk factors: the Inter99 study

OBJECTIVE

To evaluate whether five-year changes in self-reported physical activity level were associated with changes in waist circumference, weight, serum lipids and blood pressure.

METHODS

In the Inter99 study (1999-2006) in Copenhagen, Denmark, 4039 men and women (30-60 years) answered questions on lifestyle and provided blood samples and anthropometric measures at baseline and after five years. Multiple regression analyses were performed with five-year value of each cardiovascular biomarker as outcome and change in physical activity level as explanatory variable.

RESULTS

Approximately 50% of the study population were men (n=2023). Change in physical activity level was inversely associated with change in weight (p<0.0001), waist (p<0.0001), diastolic blood pressure (p=0.04), total cholesterol (p=0.006), LDL (p=0.007), triglycerides (p=0.02) and with a composite risk score "the Copenhagen risk score" (p<0.0001), and positively associated with HDL in men (p=0.01).

CONCLUSION

Five-year changes in physical activity level were significantly associated with relevant changes in weight, waist circumference, diastolic BP and serum lipids in a population-based cohort of adult men and women. Change in physical activity level induced a significant change in HDL concentration in men only. Women's use of hormone replacement therapy may partly explain this gender difference.

Distinct trajectories of leisure time physical activity and predictors of trajectory class membership: a 22 year cohort study

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BACKGROUND

Prospective studies linking social factors to long term patterns of physical activity are lacking. In this 22 year longitudinal study, we seek to identify long term patterns of involvement in leisure time physical activity (LTPA), and explore socioeconomic and demographic predictors of distinct LTPA trajectories.

METHODS

Among 2102 individuals aged 18-60 years in 1981 who participated in the 1981 Canada Fitness Survey/1988 Campbell's Survey of Well-Being, 1186 (56.4%) completed questionnaires for the 2002/04 follow-up. Complete data on LTPA at all 3 surveys were available for 884 participants. Latent class growth analysis was used to identify major classes of LTPA trajectories; predictors of class membership were identified using polytomous logistic regression.

RESULTS

Four latent classes were identified: inactive, increasers, active, and decreasers (53%, 26%, 12%, and 9% of participants, respectively). Women, older participants, those with lower household income, and with lower educational attainment, were significantly less likely to follow active (Vs. inactive) trajectories of LTPA. Disadvantaged groups with respect to education and income were also significantly more likely to follow decreasing (Vs. active) trajectories.

CONCLUSION

There is a need for continued efforts to increase overall population levels of LTPA, particularly among socially disadvantaged groups with respect to income and education, who are most likely to experience unfavorable trajectories of LTPA.

Nine-year changes in cardiovascular disease risk factors with weight maintenance in the atherosclerosis risk in communities cohort

Few studies have focused on the impact of weight maintenance on cardiovascular disease risk factors or addressed whether changes differ by baseline weight status and medication usage. The authors examined these issues using 9 years of follow-up data on 3,235 men and women from the Atherosclerosis Risk in Communities (ARIC) Study who were aged 45-64 years at baseline (1987-1989). In participants not using medications, glucose (3.0 mg/dl, 95% confidence interval (CI): 2.4, 3.5) and triglycerides (10.1 mg/dl, 95% CI: 8.3, 11.9) increased, while total cholesterol (-9.6 mg/dl, 95% CI: -10.6, -8.6), low density lipoprotein cholesterol (-9.9 mg/dl, 95% CI: -10.9, -9.0), and high density lipoprotein cholesterol (-1.7 mg/dl, 95% CI: -2.1, -1.3) decreased. Systolic blood pressure (7.9 mmHg, 95% CI: 7.3, 8.4) increased, but diastolic blood pressure (-1.1 mmHg, 95% CI: -1.4, -0.7) declined. Normal weight (body mass index: 18.5-<25.0 kg/m(2)) participants had smaller increases in glucose compared with obese (body mass index: >/=30.0 kg/m(2)) participants. In contrast, the authors found less favorable changes in total, low density lipoprotein, and high density lipoprotein cholesterol, triglycerides, and diastolic blood pressure among normal weight compared with obese participants who maintained their weight. These patterns were similar across weight status groups regardless of medication usage.

The Clinical Biochemistry of Obesity—More Than Skin Deep

While obesity has a high prevalence in developed countries, the routine abnormalities seen from the clinical biochemistry laboratory that may be caused by obesity related pathology do not seem to be as common. Insulin resistance, which is often associated with obesity, is difficult to assess as formal procedures are too complex for clinical practice. Furthermore the interpretation of insulin levels is hampered by their in vivo variability, assay differences and the lack of reference intervals from an unaffected reference population. Interpretation of fasting glucose levels between 5.5 and 6.0mmol/L are also being debated however, it is useful to understand the age related changes in this parameter, which may also be due to increasing obesity in the reference population. The association of obesity and dyslipidaemia in the metabolic syndrome should focus on elevated triglycerides (>1.5mmol/L), which is associated with low HDLC and correlates with atherogenic small dense LDL. High triglycerides are also predictive of fatty liver and the common abnormality of an elevated ALT may not be appreciated if laboratories allow their reference intervals to increase as the population gets more obese with aging. SHBG levels fall with insulin resistance/hyperinsulinaemia and this needs to be taken into account when testosterone is measured. However, low SHBG is showing huge potential as a disease and prognostic marker in obesity. These commonly available tests provide useful insights for the obese patient and their utility may improve with future research into the growing problem of obesity.

Changes in risk factors for cardiovascular disease by baseline weight status in young adults who maintain or gain weight over 15 years: the CARDIA study

OBJECTIVES

To examine whether changes in cardiovascular disease (CVD) risk factors differ by baseline weight status among young adults who maintained or gained weight.

DESIGN

Longitudinal cohort study.

SUBJECTS

White and African Americans who either maintained (+/-5 pounds; n=488) or gained (>5 pounds; n=2788) weight over 15 years.

MEASUREMENTS

Anthropometrics and CVD risk factors were measured at baseline (1985-1986) and follow-up. Participants were classified as normal weight (body mass index (BMI) 18.5-24.9 kg/m2) or overweight (BMI >or=25 kg/m2) at baseline. Multivariable models were stratified by ethnicity and weight change category.

RESULTS

Normal weight maintainers tended to have more favorable risk factors at baseline and follow-up than overweight maintainers. Size and direction of 15-year changes in risk factors were similar by weight status, except that in white normal weight maintainers changes in high-density lipoprotein (HDL)-cholesterol (3.3 mg/dl (95% confidence interval (CI): 0.4, 6.3)) and triglycerides (-14.7 mg/dl (-25.8, -3.7)) were more favorable. Weight gain was associated with unfavorable changes in risk factors. Weight gainers normal weight at baseline had less adverse changes in glucose, blood pressure, HDL-cholesterol (whites only) and triglycerides (African Americans only) than overweight gainers. However, normal weight African-American weight gainers had more adverse changes in total (3.1 mg/dl (0.2, 6.1)) and low-density lipoprotein-cholesterol (3.4 mg/dl (0.6, 6.3)).

CONCLUSIONS

Baseline weight status does not appear to influence the size or direction of risk factor changes among adults who maintained their weight over 15 years. In contrast, weight gain was associated with changes in some risk factors differentially by baseline weight status.

The definition of weight maintenance

There is currently no consensus on the definition of weight maintenance in adults. Issues to consider in setting a standard definition include expert opinion, precedents set in previous studies, public health and clinical applications, comparability across body sizes, measurement error, normal weight fluctuations and biologic relevance. To be useful, this definition should indicate an amount of change less than is clinically relevant, but more than expected from measurement error or fluctuations in fluid balance under normal conditions. It is an advantage for the definition to be graded by body size and to be easily understood by the public as well as scientists. Taking all these factors into consideration, the authors recommend that long-term weight maintenance in adults be defined as a weight change of <3% of body weight.

Increasing lifestyle physical activity in patients with depression or other serious mental illness

People with severe and persistent mental illness are more likely to be overweight and to suffer from obesity-related illnesses such as diabetes and heart disease than healthy individuals. Lifestyle change interventions that emphasize integrating physical activity into daily life have not been studied extensively in people with mental illness. The authors present the results of an initial feasibility study of a lifestyle modification program for individuals with serious mental illness. Thirty-nine individuals with depression or other serious mental illness were recruited from three different mental health facilities to attend an 18-week lifestyle intervention program promoting physical activity and healthy eating. At each session, participants discussed topics related to healthy lifestyle changes and participated in group walks. Data were collected at baseline, 6 weeks, and 18 weeks. The results demonstrated that individuals who have depression and other serious mental illnesses can participate in a lifestyle intervention program. Participants who attended the final follow-up session had lost weight over the course of the intervention. Study retention was a problem. However, the cost of this type of group-based lifestyle intervention was relatively low, so that such an intervention for this high-risk group may still be cost-effective.

A longitudinal study of physical activity and heart rate recovery: CARDIA, 1987-1993

PURPOSE

Autonomic nervous system function may be a mechanism by which frequent physical activity is associated with better coronary heart disease outcomes. In a diverse, population-based sample, we tested whether physical activity participation was associated with higher parasympathetic function.

METHODS

Participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study underwent symptom-limited graded exercise testing at baseline (1985-1986; N=3446) and at 7 yr follow-up (N=1627). Heart rate recovery (HRR), the difference between maximum heart rate (HR) and HR 2 min after test cessation, was used to estimate parasympathetic activity.

RESULTS

Participants who self-reported in the highest tertile of total physical activity (the sum of moderate- and heavy-intensity activities) had significantly faster HRR than participants in the lowest tertile (45.1 vs 41.8 beats.min, P<0.01), and the odds of having abnormal HRR (<or=22 beats.min) were 1.9 (95% confidence interval: 1.1, 3.4) times greater in the lowest versus the highest tertile after adjustment for age, race, gender, body mass index, smoking status, and diastolic blood pressure. Findings were consistent across strata of covariates. On average, HRR declined 2.5 beats.min over 7 yr. HRR declined the least among participants whose physical activity increased (-1.3 beats.min) or remained stable (-1.8 beats.min), compared with participants whose physical activity decreased (-3.6 beats.min; P<0.01 vs increase or stable).

CONCLUSIONS

In this diverse, population-based sample, physical activity was associated with faster HRR from an exercise treadmill test. Regular physical activity may blunt age-related declines in autonomic nervous system function.

Premature coronary artery disease: clinical risk factors and prognosis

Coronary artery disease (CAD) that becomes manifest in young adults can have devastating consequences. Additionally, the study of young patients with CAD may provide insight into the genetic basis of coronary disease. Over the past few years, our understanding of risk factors in this population has been expanded to include social, environmental, and emotional factors. The identification of genetic markers for disease is just beginning. Also, it has recently been shown that CAD in young adults has a poor long-term prognosis, meaning that clinicians caring for these patients must be aggressive in risk factor control.

Understanding variability in time spent in selected locations for 7-12-year old children

This paper summarizes a series of analyses of clustered, sequential activity/location data collected by Harvard University for 160 children aged 7-12 years in Southern California (Geyh et al., 2000). The main purpose of the paper is to understand intra- and inter-variability in the time spent by the sample in the outdoor location, the location exhibiting the most variability of the ones evaluated. The data were analyzed using distribution-free hypothesis-testing (K-S tests of the distributions), generalized linear modeling techniques, and random-sampling schemes that produced "cohorts" whose descriptive statistical characteristics were evaluated against the original dataset. Most importantly, our analyses indicate that subdividing the population into appropriate cohorts better replicates parameters of the original data, including the interclass correlation coefficient (ICC), which is a relative measure of the intra- and inter-individual variability inherent in the original data. While the findings of our analyses are consistent with previous assessments of "time budget" and physical activity data, they are constrained by the rather homogeneous sample available to us. Owing to a general lack of longitudinal human activity/location data available for other age/gender cohorts, we are unable to generalize our findings to other population subgroups.

Obesity and dyslipidemia

The primary dyslipidemia related to obesity is characterized by increased triglycerides, decreased HDL levels, and abnormal LDL composition. Much work has been done to elucidate the pathogenesis of the dyslipidemia of obesity, which seems to be closely related to insulin resistance in obese individuals; however, more studies in humans are needed to further understand the metabolic mechanisms underlying the changes, and to distinguish between the roles of insulin resistance and body fat in the lipoprotein changes. The dyslipidemia associated with obesity no doubt plays a major role in the development of atherosclerosis and CVD in obese individuals. All of the components of the dyslipidemia, including higher triglycerides, decreased HDL levels, and increased small, dense LDL particles, have been shown to be atherogenic. Weight loss and exercise, even if they do not result in normalization of body weight, can improve this dyslipidemia and thus reduce CVD risk. In addition, obese individuals should be targeted for intense lipid-lowering therapy, when necessary.

Relative influence of diet and physical activity on cardiovascular risk factors in urban Chinese adults

OBJECTIVE

The relative influence of dietary factors vs physical activity on cardiovascular risk factors are poorly understood. We investigated these factors in a population whose traditional diet may have both positive (high plant-based) and negative (high refined carbohydrate) aspects, and whose physical activity levels (PALs) vary widely.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 130 weight stable adults aged 35-49 y (BMI 18-35 kg/m(2)) living in urban Beijing, China.

MEASUREMENTS

Dietary intake (by food frequency questionnaire), PAL as the ratio of predicted total to resting energy expenditure), percent body fat (by deuterium oxide dilution), and central adiposity (waist circumference and waist to hip ratio) were assessed. Biochemical parameters (total cholesterol, low- and high-density lipoprotein cholesterol (LDL-C; HDL-C), triglyceride (TG), apolipoproteins A-I and B, glucose, insulin, and homocysteine and its related vitamins), blood pressure and presence of the metabolic syndrome (having >/=3 risk factors of central adiposity, HDL-C, TG, glucose, blood pressure) were also examined.

RESULTS

Mean values for cardiovascular risk factors were relatively low, but 19% of subjects had the metabolic syndrome. Using validated methods for measuring food intake and energy expenditure, we found that an adverse cardiovascular risk profile was associated with a diet high in carbohydrate, low in polyunsaturated fat, and low in fruit and vegetables, independent of body fatness and its distribution. While dietary factors predicted individual cardiovascular risk factors more consistently than PAL, avoidance of low PAL reduced the risk of having the metabolic syndrome.

CONCLUSION

These results suggest that, regardless of total body fatness and fat distribution, multiple unfavorable dietary factors and low physical activity independently increase the risk for cardiovascular disease. Avoidance of a sedentary lifestyle additionally reduces the risk of developing the metabolic syndrome.

Using human activity data in exposure models: analysis of discriminating factors

This paper tests factors thought to be important in explaining the choices people make in where they spend time. Three aggregate locations are analyzed: outdoors, indoors, and in-vehicles for two different sample groups: a year-long (longitudinal) sample of one individual and a cross-sectional sample of 169 individuals from the US Environmental Protection Agency's Consolidated Human Activity Database (CHAD). The cross-sectional sample consists of persons similar to the longitudinal subject in terms of age, work status, education, and residential type. The sample groups are remarkably similar in the time spent per day in the tested locations, although there are differences in participation rates: the percentage of days frequenting a particular location. Time spent outdoors exhibits the most relative variability of any location tested, with in-vehicle time being the next. The factors found to be most important in explaining daily time usage in both sample groups are: season of the year, season/temperature combinations, precipitation levels, and day-type (work/nonwork is the most distinct, but weekday/weekend is also significant). Season, season/temperature, and day-type are also important for explaining time spent indoors. None of the variables tested are consistent in explaining in-vehicle time in either the cross-sectional or longitudinal samples. Given these findings, we recommend that exposure modelers subdivide their population activity data into at least season/temperature, precipitation, and day-type "cohorts" as these factors are important discriminating variables affecting where people spend their time.

Relation of self-rated measures of physical activity to multiple risk factors of insulin resistance syndrome in young adults: the Bogalusa Heart Study

The relation of self-rated measures of physical activity to multiple risk factors of insulin resistance syndrome (IRS) was examined in African American (n = 409) and white (n = 1,011) young adults aged 20 to 38 years enrolled in the Bogalusa Heart Study. Physical activity was assessed in terms of work activity, leisure-time activity, television watching, and video game playing by a questionnaire. Waist circumference, blood pressure, total to high-density lipoprotein cholesterol ratio, and insulin resistance index showed a consistent inverse trend with leisure-time activity (P < 0.01) and a positive trend with hours of inactivity (P < 0.01) after adjusting for age, race, and sex. An inverse relationship was seen between leisure-time activity and mean number of risk factors (>75th percentile for age, race, and sex) (P < 0.001), whereas a positive relationship was seen with hours of inactivity (P < 0.001). Moderately to very active individuals versus inactive individuals had a reduced relative risk of having > or =3 risk factors (P < 0.05); conversely, excess hours of inactivity increased the relative risk (P < 0.05). Thus, leisure-time activity and hours of inactivity are important predictors of multiple cardiovascular risk variables of IRS in young adults.