Eric J. Shiroma

Physical Activity and Cardiovascular Health Lessons Learned From Epidemiological Studies Across Age, Gender, and Race/Ethnicity

In 1953, Morris et al1,2 published the findings from a study showing that bus conductors in London, who spent their working hours walking the length of the buses as well as climbing up and down the stairs of the English double-decker buses to collect fares, experienced half the coronary heart disease (CHD) mortality rates of their driver counterparts, who spent their day sitting behind the wheel. Investigators hypothesized that it was the physical activity of work that protected the conductors from developing CHD, at the same time realizing that other factors may also play a role because the conductors were smaller in size, as evidenced by their smaller uniform sizes. Thus was born the field of “physical activity epidemiology”: formal epidemiological investigations into the associations of physical activity with many health outcomes.4 Since the initial observations of Morris et al, many other studies have been conducted, yielding similar results: Active people have lower rates of CHD and cardiovascular disease (CVD) than inactive ones.5–7 These findings have been supported by plausible biological mechanisms, which are detailed in other articles in this review series. The collective body of evidence led the American Heart Association in 1992 to recognize physical inactivity as a risk factor for CHD and CVD8 and led the Surgeon General in 1996 to conclude that “regular physical activity or cardiorespiratory fitness decreases the risk of CVD … and CHD.”9 The basis for these conclusions was derived primarily from studies in men and in white populations; for example, in a 1990 meta-analysis of physical activity in the prevention of CHD10 that included 33 studies, women were subjects in 5 studies, and racial/ethnic minorities were the focus of 2 studies. In 2008, the federal government issued its first-ever physical activity guidelines for Americans11 based …

Using accelerometers to measure physical activity in large-scale epidemiological studies: issues and challenges

Background The current guidelines for aerobic activity require that adults carry out ≥150 min/week of moderate-intensity physical activity, with a large body of epidemiological evidence showing this level of activity to decrease the incidence of many chronic diseases. Less is known about whether light-intensity activities also have such benefits, and whether sedentary behaviour is an independent predictor of increased risks of these chronic diseases, as imprecise assessments of these behaviours and cross-sectional study designs have limited knowledge to date. Methods Recent technological advances in assessment methods have made the use of movement sensors, such as the accelerometer, feasible for use in longitudinal, large-scale epidemiological studies. Several such studies are collecting sensor-assessed, objective measures of physical activity with the aim of relating these to the development of clinical endpoints. This is a relatively new area of research; thus, in this article, we use the Womens Health Study (WHS) as a case study to illustrate the challenges related to data collection, data processing and analyses of the vast amount of data collected. Results The WHS plans to collect 7 days of accelerometer-assessed physical activity and sedentary behaviour in ∼18 000 women aged ≥62 years. Several logistical challenges exist in collecting data; nonetheless, as of 31 August 2013, 11 590 women have already provided some data. In addition, the WHS experience on data reduction and data analyses can help inform other similar large-scale epidemiological studies. Conclusions Important data on the health effects of light-intensity activity and sedentary behaviour will emerge from large-scale epidemiological studies collecting objective assessments of these behaviours.

Patterns of accelerometer-assessed sedentary behavior in older women.

Recent studies suggest a high volume of sedentary behavior may be a risk factor for adverse health outcomes.1 However, few data exist on how this behavior is patterned (eg, does most sedentary behavior occur in a few long bouts or in many short bouts?) and whether sedentary patterns are relevant for health. We examined details of sedentary behavior among older women. Because physical activity is influenced by age, body mass index (BMI; calculated as weight in kilograms divided by height in meters squared), and smoking status, we further examined sedentary behavior in relation to these characteristics.

Assessing Daily Physical Activity in Older Adults: Unraveling the Complexity of Monitors, Measures, and Methods

At the 67th Gerontological Society of America Annual Meeting, a preconference workshop was convened to discuss the challenges of accurately assessing physical activity in older populations. The advent of wearable technology (eg, accelerometers) to monitor physical activity has created unprecedented opportunities to observe, quantify, and define physical activity in the real-world setting. These devices enable researchers to better understand the associations of physical activity with aging, and subsequent health outcomes. However, a consensus on proper methodological use of these devices in older populations has not been established. To date, much of the validation research regarding device type, placement, and data interpretation has been performed in younger, healthier populations, and translation of these methods to older populations remains problematic. A better understanding of these devices, their measurement properties, and the data generated is imperative to furthering our understanding of daily physical activity, its effects on the aging process, and vice versa. The purpose of this article is to provide an overview of the highlights of the preconference workshop, including properties of the different types of accelerometers, the methodological challenges of employing accelerometers in older study populations, a brief summary of ongoing aging-related research projects that utilize different types of accelerometers, and recommendations for future research directions.

Duration and breaks in sedentary behaviour: accelerometer data from 1566 community-dwelling older men (British Regional Heart Study)

Background Sedentary behaviours are increasingly recognised as raising the risk of cardiovascular disease events, diabetes and mortality, independently of physical activity levels. However, little is known about patterns of sedentary behaviour in older adults. Methods Cross-sectional study of 1566/3137 (50% response) men aged 71–91 years from a UK population-based cohort study. Men wore a GT3x accelerometer over the hip for 1 week in 2010–2011. Mean daily minutes of sedentary behaviours, percentage of day in sedentary behaviours, sedentary bouts and breaks were calculated and summarised by health and demographic characteristics. Results 1403 ambulatory men aged 78.4 years (SD=4.6 years) with ≥600 min of accelerometer wear on ≥3 days had complete data on covariables. Men spent on average 618 min (SD=83), or 72% of their day in sedentary behaviours (<100 counts/min). On average, men accumulated 72 spells of sedentary behaviours per day, with 7 breaks in each sedentary hour. Men had on average 5.1 sedentary bouts of ≥30 min, which accounted for 43% of sedentary time, and 1.4 bouts of ≥60 min, which accounted for 19% of daily sedentary time. Men who were over 80 years old, obese, depressed and had multiple chronic conditions accumulated more sedentary time and spent more time in longer sedentary bouts. Conclusions Older men spend nearly three quarters of their day in sedentary behaviours, mostly accumulated in short bouts, although bouts lasting ≥30 min accounted for nearly half of the sedentary time each day. Men with medical risk factors were more likely to also display sedentary behaviour.

Do Moderate‐Intensity and Vigorous‐Intensity Physical Activities Reduce Mortality Rates to the Same Extent?

Background Limited data exist directly comparing the relative benefits of moderate‐ and vigorous‐intensity activities with all‐cause and cardiovascular (CV) disease mortality rates when controlling for physical activity volume. Methods and Results We followed 7979 men (Harvard Alumni Health Study, 1988–2008) and 38 671 women (Womens Health Study, 1992–2012), assessing their physical activity and health habits through repeated questionnaires. Over a mean follow‐up of 17.3 years in men and 16.4 years in women, there were 3551 deaths (1077 from CV disease) among men and 3170 deaths (620 from CV disease) among women. Those who met or exceeded an equivalent of the federal guidelines recommendation of at least 150 minutes of moderate‐intensity activity, 75 minutes of vigorous‐intensity activity, or a combination of the 2 that expended similar energy experienced significantly lower all‐cause and CV disease–related mortality rates (men, 28% to 36% and 31% to 34%, respectively; women: 38% to 55% and 22% to 44%, respectively). When comparing different combinations of moderate‐ and vigorous‐intensity activity and all‐cause mortality rates, we observed sex‐related differences. Holding constant the volume of moderate‐ to vigorous‐intensity physical activity, men experienced a modest additional benefit when expending a greater proportion of moderate‐ to vigorous‐intensity physical activity in vigorous‐intensity activities (Ptrend=0.04), but women did not (Ptrend<0.001). Moderate‐ to vigorous‐intensity physical activity composition was not associated with further cardiovascular mortality rate reductions in either men or women. Conclusions The present data support guidelines recommending 150 minutes of moderate‐intensity activity per week, 75 minutes of vigorous‐intensity activity per week, or an equivalent combination for mortality benefits. Among men, but not women, additional modest reductions in all‐cause mortality rates are associated with a greater proportion of moderate‐ to vigorous‐intensity physical activity performed at a vigorous intensity.

Comparison of physical activity assessed using hip- and wrist-worn accelerometers.

OBJECTIVES It is unclear how physical activity estimates differ when assessed using hip- vs wrist-worn accelerometers. The objective of this study was to compare physical activity assessed by hip- and wrist-worn accelerometers in free-living older women. DESIGN A cross-sectional study collecting data in free-living environment. METHODS Participants were from the Womens Health Study, in which an ancillary study is objectively measuring physical activity using accelerometers (ActiGraph GT3X+). We analyzed data from 94 women (mean (SD) age=71.9 (6.0) years) who wore a hip-worn and wrist-worn accelerometers simultaneously for 7 days. RESULTS Using triaxial data (vector magnitude, VM), total activity volume (counts per day) between the two locations was moderately correlated (Spearmans r=0.73). Hip and wrist monitors wear locations identically classified 71% individuals who were at the highest 40% or lowest 40% of their respective distributions. Similar patterns and slightly stronger agreements were observed when examining steps instead of VM counts. CONCLUSIONS Accelerometer-assessed physical activity using hip- vs wrist-worn devices was moderately correlated in older, free-living women. However, further research needs to be conducted to examine comparisons of specific activities or physical activity intensity levels.

Physical activity and weight gain prevention in older men.

Background:Physical activity and adiposity are important predictors of mortality, even in older individuals. However, it is unclear how much physical activity is needed to prevent weight gain in older persons.Purpose:To examine the associations of different amounts of physical activity with weight gain prevention in older men.Methods:A total of 5973 healthy men (mean age, 65.0 years) from the Harvard Alumni Health Study were followed from 1988 to 1998. At baseline (1988), in 1993 and 1998, men reported their recreational physical activity and body weight. Physical activity was categorized as: <7.5 metabolic equivalent (MET)-h per week (7.5 MET-h per week corresponds to the minimum required by the 2008 US federal guidelines), 7.5 to <21 MET-h per week (21 MET-h per week corresponds to the 2002 Institute of Medicine (IOM) guideline) and ⩾21 MET-h per week. Meaningful weight gain was defined as an increase of ⩾3% of body weight.Results:Overall, weight tended to be stable over any 5-year period; mean change, −0.08 (s.d.=4.44) kg. However, ∼21% of men experienced meaningful weight gain over any 5-year period. In multivariate analyses, compared with men expending ⩾21 MET-h per week, those expending 7.5 to <21 MET-h per week had an odds ratio (OR) of 1.35 (95% confidence interval: 1.03, 1.77) for meaningful weight gain, and men expending <7.5 MET-h per week, an OR of 1.16 (1.01, 1.33; P trend=0.09).Conclusions:Among older men, those with lesser levels of physical activity were more likely to gain weight than men satisfying the 2002 IOM guidelines of ⩾21 MET-h per week (∼60 min day−1 of moderate-intensity physical activity).

Comparison of Self-Reported and Accelerometer-Assessed Physical Activity in Older Women

Background Self-reported physical activity measures continue to be validated against accelerometers; however, the absence of standardized, accelerometer moderate-to-vigorous physical activity (MVPA) definitions has made comparisons across studies difficult. Furthermore, recent accelerometer models assess accelerations in three axes, instead of only the vertical axis, but validation studies have yet to take incorporate triaxial data. Methods Participants (n = 10 115) from the Women’s Health Study wore a hip-worn accelerometer (ActiGraph GT3X+) for seven days during waking hours (2011–2014). Women then completed a physical activity questionnaire. We compared self-reported with accelerometer-assessed MVPA, using four established cutpoints for MVPA: three using only vertical axis data (760, 1041 and 1952 counts per minute (cpm)) and one using triaxial data (2690 cpm). Results According to self-reported physical activity, 66.6% of women met the US federal physical activity guidelines, engaging in ≥150 minutes per week of MVPA. The percent of women who met guidelines varied widely depending on the accelerometer MVPA definition (760 cpm: 50.0%, 1041 cpm: 33.0%, 1952 cpm: 13.4%, and 2690 cpm: 19.3%). Conclusions Triaxial count data do not substantially reduce the difference between self-reported and accelerometer-assessed MVPA.

Accelerometer-Measured Physical Activity and Sedentary Behavior in Relation to All-Cause Mortality: The Women’s Health Study

Physical inactivity is estimated to cause as many deaths globally each year as smoking.1 Current guidelines recommend ≥150 min/wk of moderate-intensity aerobic physical activity (PA) and muscle-strengthening exercises on ≥2 d/wk.2 These guidelines are based primarily on studies using self-reported moderate- to vigorous-intensity PA (MVPA).2 Technological developments now enable device assessments of light-intensity PA (LPA) and sedentary behavior, and well-designed studies with such assessments that investigate clinical outcomes are needed for updating current guidelines. Here, we present data from the WHS (Women’s Health Study). From 2011 to 2015, 18 289 of 29 494 living women agreed to participate; 1456 were ineligible because they could not walk unassisted outside the home. Women provided written consent to participate, and the study was approved by the institutional review board committee of Brigham and Women’s Hospital. Participants were younger and healthier than nonparticipants. Women were mailed a triaxial accelerometer (ActiGraph GT3X+, ActiGraph Corp) and asked to wear it on the hip for 7 days (except during sleep and water-based activities) and then to mail back the device. A total of 17 708 women wore their devices. Of 17 466 devices recording data (242 devices failed), 16 741 (96%) had data from ≥10 h/d on ≥4 days (convention for compliant wear). Women were followed up through December 31, 2015, for mortality, with deaths confirmed with medical records, death certificates, or the National Death Index. We examined the associations of total volume of PA (total …