47 research outputs found
Longitudinal Evaluations of Objectively Measured Physical Activity: Capturing the Full Spectrum of Duration and Intensity
Most physical activity research to date narrows its focus toward intensities and durations only encompassed in the Physical Activity Guidelines of moderate to vigorous intensity in at least 10 minute bouts (MVPA-10). Examining activity in this manner excludes light activity and shorter bouts, sometimes referred to as baseline physical activity (BPA) as it consists of the activity accumulated during daily life at durations and/or intensities below what is recommended. This dissertation provides an evaluation of the entire spectrum of physical activity (PA). Physical activity was studied in a unique way by looking at MVPA-10, then adding shorter bouts and light intensity to see if these additions further influence study outcomes. This dissertation incorporated this concept into the analyses while linking behavioral investigations of physical activity to a physiological investigation of how such activity influences adiposity and weight. Thus, it transitioned from what characteristics influence physical activity behavior to how physical activity influences health. Three separate papers used this concept to 1) examine the intrapersonal-level determinants of the full spectrum of PA 2) examine how the total number of life events and the self-reported stress of life events influences the full spectrum of PA; and 3) examine the longitudinal relationship of the full spectrum of PA with adiposity and weight. This dissertation used objectively measured physical activity data collected as part of The Energy Balance Study to examine the three specific aims. The purpose of the Energy Balance Study was to examine the extent to which variation in total energy expenditure (TEE) and variation in total energy intake (TEI) contribute to changes in body weight and fat among adults. A secondary aim was to examine specific components of TEE and TEI that drive changes in body weight and fat. This dissertation contributes answers to this secondary aim, by examining the physical activity component of TEE.
Study 1 showed that intrapersonal variables within categories of biological, socioeconomic, family structure, behavioral, and psychological can influence activity. The associated characteristics differ based on whether physical activity is quantified as MVPA-10, total MVPA, or total PA. Adding components of baseline PA, first short bouts of total MVPA followed by light intensity PA influences the results.
In the second study, the average number and associated stress of life events per quarter did not have much influence on physical activity. However, many life events when examined separately had significant associations with MVPA-10, total MVPA and total PA. For young adult men, changing jobs and marriage had negative impacts on activity while starting/ending a relationship and beginning a mortgage had positive influences. For young adult women, starting a new job, moving, engagement, and the loss of a family/friend had negative consequence while quitting a job resulted in increases in PA. The degree of influence on activity often went beyond the typical recommendations of MVPA in 10 minute bouts.
In the third study, physical activity had an influence on various anthropometric measures and varied by gender. The accumulation of greater amounts of activity was associated with a lower body fat percentage for both men and women. There were also associations with PA for waist circumference, hip circumference, and BMI for the women. For all anthropometric associations there were similar degrees of association for MVPA-10 and total MVPA, suggesting that the accumulation of all MVPA regardless of bout length can have a similar influence on anthropometrics. The association of anthropometrics with total PA was typically half of the impact when comparing the MVPA categories. Thus an increase of MVPA has a greater influence on anthropometric outcomes than an increase in total PA
Subjective Estimation of Physical Activity Using the IPAQ Varies by Fitness Level
Background: Subjective measures of moderate and vigorous physical activity (MVPA) rely on ârelativeâ intensity while objective measures capture âabsoluteâ intensity, thus fit individuals may perceive the same activity differently than unfit individuals. Methods: Adults (N=211) wore the SenseWear Armband (SWA) for ten consecutive days to objectively assess sedentary time and MVPA. On day eight participants completed the International Physical Activity Questionnaire (IPAQ) to subjectively assess sitting time and MVPA. Fitness was assessed via a maximal treadmill test, and participants were classified as âunfitâ if the result was in the bottom tertile of the study population by sex or âfitâ if in the upper two tertiles. Results: Overall, estimates of MVPA between the IPAQ and SWA were not significantly different (IPAQ minus SWA, 67.4±919.1 MVPA minutes/week, P=.29). However, unfit participants overestimated MVPA using the IPAQ by 37.3% (P=.02), but fit participants did not (P=.99). This between-group difference was due to overestimation using the IPAQ of moderate activity by 93.8 minutes/week among the unfit individuals, but underestimation of moderate activity among the fit participants by 149.4 minutes/week. Conclusion: Subjective measures of MVPA using the IPAQ varied by fitness category, with unfit participants overestimating their MVPA and fit participants accurately estimating their MVPA
Low fitness partially explains resting metabolic rate differences between African American and white women
Background High levels of obesity among African American women have been hypothesized to be partially resultant from a lower resting metabolic rate compared with white women. The aim of the current study was to determine if differences in cardiorespiratory fitness and moderate-to-vigorous physical activity are associated with differences in resting metabolic rate among free-living young adult African American women and white women. Methods Participants were 179 women (white women n = 141, African American women n = 38, mean age = 27.7 years). Resting metabolic rate was measured using indirect calorimetry, body composition using dual energy x-ray absorptiometry, cardiorespiratory fitness via maximal treadmill test, and moderate-to-vigorous physical activity using an activity monitor. Results African American women had higher body mass index, fat mass, and fat-free mass compared with white women but lower levels of cardiorespiratory fitness. No differences were observed between African American and white women in resting metabolic rate when expressed as kcal/day (1390.8 ± 197.5 vs 1375.7 ± 173.6 kcal/day, P =.64), but African American women had a lower resting metabolic rate when expressed relative to body weight (2.56 ± 0.30 vs 2.95 ± 0.33 mL/kg/min,
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Estimated Impact of Achieving Optimal Cardiovascular Health Among US Adults on Cardiovascular Disease Events
Background Better cardiovascular health (CVH) scores are associated with lower risk of cardiovascular disease (CVD). However, estimates of the potential population-level impact of improving CVH on US CVD event rates are not currently available. Methods and Results Using data from the National Health and Nutrition Examination Survey 2011 to 2016 (n=11 696), we estimated the proportions of US adults in CVH groups. Levels of 7 American Heart Association CVH metrics were scored as ideal (2 points), intermediate (1 point), or poor (0 points), and summed to define overall CVH (low, 0-8 points; moderate, 9-11 points; or high, 12-14 points). Using individual-level data from 7 US community-based cohort studies (n=30 447), we estimated annual incidence rates of major CVD events by levels of CVH. Using the combined data sources, we estimated population attributable fractions of CVD and the number of CVD events that could be prevented annually if all US adults achieved high CVH. High CVH was identified in 7.3% (95% CI, 6.3%-8.3%) of US adults. We estimated that 70.0% (95% CI, 56.5%-79.9%) of CVD events were attributable to low and moderate CVH. If all US adults attained high CVH, we estimated that 2.0 (95% CI, 1.6-2.3) million CVD events could be prevented annually. If all US adults with low CVH attained moderate CVH, we estimated that 1.2 (95% CI, 1.0-1.4) million CVD events could be prevented annually. Conclusions The potential benefits of achieving high CVH in all US adults are considerable, and even a partial improvement in CVH scores would be highly beneficial
Prospective Association of Daily Steps with Cardiovascular Disease: A Harmonized Meta-Analysis
Background:
Taking fewer than the widely promoted â10â000 steps per dayâ has recently been associated with lower risk of all-cause mortality. The relationship of steps and cardiovascular disease (CVD) risk remains poorly described. A meta-analysis examining the doseâresponse relationship between steps per day and CVD can help inform clinical and public health guidelines.
Methods:
Eight prospective studies (20â152 adults [ie, â„18 years of age]) were included with device-measured steps and participants followed for CVD events. Studies quantified steps per day and CVD events were defined as fatal and nonfatal coronary heart disease, stroke, and heart failure. Cox proportional hazards regression analyses were completed using study-specific quartiles and hazard ratios (HR) and 95% CI were meta-analyzed with inverse-varianceâweighted random effects models.
Results:
The mean age of participants was 63.2±12.4 years and 52% were women. The mean follow-up was 6.2 years (123â209 person-years), with a total of 1523 CVD events (12.4 per 1000 participant-years) reported. There was a significant difference in the association of steps per day and CVD between older (ie, â„60 years of age) and younger adults (ie, <60 years of age). For older adults, the HR for quartile 2 was 0.80 (95% CI, 0.69 to 0.93), 0.62 for quartile 3 (95% CI, 0.52 to 0.74), and 0.51 for quartile 4 (95% CI, 0.41 to 0.63) compared with the lowest quartile. For younger adults, the HR for quartile 2 was 0.79 (95% CI, 0.46 to 1.35), 0.90 for quartile 3 (95% CI, 0.64 to 1.25), and 0.95 for quartile 4 (95% CI, 0.61 to 1.48) compared with the lowest quartile. Restricted cubic splines demonstrated a nonlinear association whereby more steps were associated with decreased risk of CVD among older adults.
Conclusions:
For older adults, taking more daily steps was associated with a progressively decreased risk of CVD. Monitoring and promoting steps per day is a simple metric for clinicianâpatient communication and population health to reduce the risk of CVD
Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts
Background Although 10000 steps per day is widely promoted to have health benefits, there is little evidence to support
this recommendation. We aimed to determine the association between number of steps per day and stepping rate
with all-cause mortality.
Methods In this meta-analysis, we identified studies investigating the effect of daily step count on all-cause mortality
in adults (aged â„18 years), via a previously published systematic review and expert knowledge of the field. We asked
participating study investigators to process their participant-level data following a standardised protocol. The primary
outcome was all-cause mortality collected from death certificates and country registries. We analysed the doseâ
response association of steps per day and stepping rate with all-cause mortality. We did Cox proportional hazards
regression analyses using study-specific quartiles of steps per day and calculated hazard ratios (HRs) with inversevariance weighted random effects models.
Findings We identified 15 studies, of which seven were published and eight were unpublished, with study start dates
between 1999 and 2018. The total sample included 47 471 adults, among whom there were 3013 deaths (10·1 per
1000 participant-years) over a median follow-up of 7·1 years ([IQR 4·3â9·9]; total sum of follow-up across studies was
297 837 person-years). Quartile median steps per day were 3553 for quartile 1, 5801 for quartile 2, 7842 for quartile 3,
and 10 901 for quartile 4. Compared with the lowest quartile, the adjusted HR for all-cause mortality was 0·60 (95% CI
0·51â0·71) for quartile 2, 0·55 (0·49â0·62) for quartile 3, and 0·47 (0·39â0·57) for quartile 4. Restricted cubic splines
showed progressively decreasing risk of mortality among adults aged 60 years and older with increasing number of
steps per day until 6000â8000 steps per day and among adults younger than 60 years until 8000â10000 steps per day.
Adjusting for number of steps per day, comparing quartile 1 with quartile 4, the association between higher stepping
rates and mortality was attenuated but remained significant for a peak of 30 min (HR 0·67 [95% CI 0·56â0·83]) and
a peak of 60 min (0·67 [0·50â0·90]), but not significant for time (min per day) spent walking at 40 steps per min or
faster (1·12 [0·96â1·32]) and 100 steps per min or faster (0·86 [0·58â1·28]).
Interpretation Taking more steps per day was associated with a progressively lower risk of all-cause mortality, up to a
level that varied by age. The findings from this meta-analysis can be used to inform step guidelines for public health
promotion of physical activity
Assessing associations between the AURKAHMMR-TPX2-TUBG1 functional module and breast cancer risk in BRCA1/2 mutation carriers
While interplay between BRCA1 and AURKA-RHAMM-TPX2-TUBG1 regulates mammary epithelial polarization, common genetic variation in HMMR (gene product RHAMM) may be associated with risk of breast cancer in BRCA1 mutation carriers. Following on these observations, we further assessed the link between the AURKA-HMMR-TPX2-TUBG1 functional module and risk of breast cancer in BRCA1 or BRCA2 mutation carriers. Forty-one single nucleotide polymorphisms (SNPs) were genotyped in 15,252 BRCA1 and 8,211 BRCA2 mutation carriers and subsequently analyzed using a retrospective likelihood appr
Genome-Wide Association Study in BRCA1 Mutation Carriers Identifies Novel Loci Associated with Breast and Ovarian Cancer Risk
BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7Ă10-8, HR = 1.14, 95% CI: 1.09-1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4Ă10-8, HR = 1.27, 95% CI: 1.17-1.38) and 4q32.3 (rs4691139, P = 3.4Ă10-8, HR = 1.20, 95% CI: 1.17-1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific associat