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Peter T. Katzmarzyk

Background:

Although the prevalence of physical inactivity is high in Canada, few studies have assessed its public health impact.

Methods:

A cause-deleted methodology was employed to estimate the effects of physical inactivity on life expectancy. Life expectancy in 2002 was estimated from an abridged life table analysis, which was repeated after removing deaths from physical inactivity. Deaths from physical inactivity were estimated from published population-attributable fractions for coronary artery disease, stroke, hypertension, colon cancer, breast cancer, and type 2 diabetes.

Results:

Life expectancy was 79.7 y in the total population, 77.2 y in males, and 82.1 y in females. Compared to overall life expectancy, physical inactivity cause-deleted values were 0.86 y lower in the total population, 0.65 y lower in males, and 1.0 y lower in females.

Conclusions:

Life expectancy could be increased by over 10 months if Canadians could be encouraged to be physically active.

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Peter T. Katzmarzyk and Caitlin Mason

Physical activity is important for the prevention of chronic disease morbidity and mortality, and the lack of adequate levels of physical activity represents a growing public health burden around the world. The purpose of this report is to introduce the concept of the “Physical Activity Transition” and to explore the potential effects that declining physical activity levels may play on health and life expectancy as countries undergo economic and demographic changes. Physical activity is related to mortality rates in humans, and the available evidence suggests that the adoption of a lifestyle characterized by lower levels of physical activity will attenuate the expected gains in life expectancy associated with the epidemiological transition. Advances in the measurement of physical activity at work, in the home, for transport, and in leisure time in a wide variety of populations will be integral to advancing the current understanding of how macro-level factors shape physical activity patterns and patterns of morbidity and mortality.

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Peter T. Katzmarzyk and Amanda E. Staiano

Background:

The purpose of this study was to evaluate the relationship between adherence to pediatric 24-hour movement guidelines (moderate to vigorous physical activity, sedentary behavior, and sleep) and cardiometabolic risk factors.

Methods:

The sample included 357 white and African American children aged 5–18 years. Physical activity, television viewing, and sleep duration were measured using questionnaires, and the 24-hour movement guidelines were defined as ≥60 minutes per day of moderate to vigorous physical activity on ≥5 days per week, ≤ 2 hours per day of television, and sleeping 9–11 hours per night (ages 5–13 y) or 8–10 hours per night (ages 14–18 y). Waist circumference, body fat, abdominal visceral and subcutaneous adipose tissue, blood pressure, fasting triglycerides, high-density lipoprotein cholesterol, and glucose were measured in a clinical setting.

Results:

A total of 26.9% of the sample met none of the guidelines, whereas 36.4%, 28.3%, and 8.4% of the sample met 1, 2, or all 3 guidelines, respectively. There were significant associations between the number of guidelines met and body mass index, visceral and subcutaneous adipose tissue, triglycerides, and glucose. There were no associations with blood pressure or high-density lipoprotein cholesterol.

Conclusions:

Meeting more components of the 24-hour movement guidelines was associated with lower levels of obesity and several cardiometabolic risk factors. Future efforts should consider novel strategies to simultaneously improve physical activity, sedentary time, and sleep in children.

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Shirley N. Bryan and Peter T. Katzmarzyk

Background:

Physical activity is associated with a reduced risk of chronic disease. This study describes the relationship between meeting the guidelines for physical activity described in Canada’s Physical Activity Guide and heart disease, type 2 diabetes, hypertension, obesity, and low levels of general health.

Methods:

Leisure-time energy expenditure (LTEE) was calculated from leisure-time physical activities reported by adults who participated in the 2007 Canadian Community Health Survey. Respondents were classified as meeting the guidelines for physical activity or not, and were stratified by sex into quartiles of LTEE. Logistic regression was used to determine the odds for all conditions associated with not meeting the guidelines and by quartile of LTEE, adjusting for covariates.

Results:

The odds of type 2 diabetes, obesity, and fair/poor health were significantly higher among those not meeting the guidelines for both sexes and for high blood pressure among women. Significantly higher odds were seen between the lowest and highest quartiles of LTEE for type 2 diabetes and high blood pressure and across all quartiles for obesity and fair/poor health for both sexes.

Conclusions:

Canadian adults meeting the physical activity guidelines have lower odds of chronic diseases and fair/poor health than those not meeting the guidelines.

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Peter T. Katzmarzyk and Robert M. Malina

The contribution of organized sport participation to the total daily energy expenditure (TDEE) of youth was estimated in a sample of 90 males and 93 females, 12-14 years of age. TDEE and moderate-to-vigorous energy expenditure (MVEE) were estimated using a 3-day activity record. Males expended 20.4% of TDEE in youth sports; the corresponding estimate for females was 16.3%. Males and females expended 55% and 64.6%, respectively, of MVEE in youth sports. Youth who participated in organized sports had greater TDEE and MVEE, and spent less time watching television than those who did not participate. Thus, organized sport participation appears to be a significant component of daily energy expenditure among youth.

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Caitlin Mason, Peter T. Katzmarzyk, Cora L. Craig, and Lise Gauvin

Background:

This study investigates the degree to which the relationship between self-rated health and mortality is consistent across income groups in Canada and whether it can be explained by differentials in physical activity.

Methods:

A sample of 17,852 adults in the 1981 Canada Fitness Survey was followed for 13 y for mortality.

Results:

After adjusting for several confounders, there was a dose-response relationship between self-rated health and all-cause, CVD, and cancer mortality. This relationship persisted across levels of income. Physical activity was inversely related to mortality; however, the risk of mortality associated with low self-rated health did not differ significantly between activity groups.

Conclusions:

Physical activity does not appear to be a significant mediating or moderating factor in the relationship between self-rated health and mortality.

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Catrine Tudor-Locke, William D. Johnson, and Peter T. Katzmarzyk

Background:

We examined the effects of wear time on a population profile of time-stamped accelerometer outputs using the 2005−2006 National Health and Nutrition Examination Survey (NHANES) data representing 3744 adults ≥ 20 years of age.

Methods:

Outputs included activity counts, steps, and time variables: nonwear (macro-determined), sedentary behavior (<100 activity counts/minute), and time in low (100−499 activity counts/minute), light (500−2019 activity counts/minute), and moderate-to-vigorous physical activity (MVPA; ≥2020 activity counts/minute) intensities. We describe mean values according to a 24-hour clock. Analysis was repeated in a reduced data set with only those who wore the accelerometer for 60 minutes within each considered hour of the day.

Results:

Between 12:00 and 17:00, U.S. adults spend approximately 31 minutes each hour in sedentary behaviors, and approximately 14 minutes, 10 minutes, and 2 minutes in low, light, and MVPA intensity activity, respectively. Removing the effect of nonwear time, sedentary behaviors are reduced in the morning hours and increase in the evening hours.

Conclusion:

At either end of the day, nonwear time appears to distort population estimates of all accelerometer time and physical activity volume indicators, but its effects are particularly clear on population estimates of time spent in sedentary behavior.

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Catrine Tudor-Locke, William D. Johnson, and Peter T. Katzmarzyk

Background:

The purpose of this study was to examine the relationship between 2005−2006 National Health and Nutrition Examination Survey (NHANES) accelerometer-determined steps/day and activity counts/day, and between steps/day and estimates of nonwear time (as an indicator of the unmonitored day) and time spent in sedentary behaviors as well as a range of physical activity intensities.

Methods:

Linear regression models were used to characterize the relationship between steps/day, activity counts/day, estimates of wear time, and intensity categories.

Results:

1781 males (mean age = 46.5 years) and 1963 females (mean age = 47.7 years) wore accelerometers 14.0 ± SEM0.06 hours/day. The relationship between steps/day and activity counts/day was positive and strong (R 2 = .87). The relationship between steps/day and time spent in sedentary behaviors was inverse and moderate (R 2 = .25). Stronger and positive relationships were apparent between steps/day and time in light (R 2 = .69) and moderate (R 2 = .63) intensity activities. There was no discernable relationship between steps/day and time spent in low or vigorous intensity activities or with wear time.

Conclusions:

Assessed by accelerometer, steps/day explains 87% of the variation in activity counts/day, 25% of the variation in time in sedentary behaviors, 69% of time in light intensity, and 63% of time in moderate intensity.