The effects of age, birth cohort and survey period on leisure-time physical activity by Australian adults: 1990-2005

The prevalence of obesity continues to rise with many factors contributing to energy imbalance. Leisure-time physical activity (LTPA) has been proposed as one solution to counteract increasing energy intakes. The present study determined whether age, birth cohort and period of survey had independent effects on time, volume and energy expended in LTPA by Australian adults from 1990 to 2005. Adults were categorised into twelve age groups (5-year intervals from 20-24 years to >75 years), four survey periods (1990, 1995, 2000 and 2005) and fifteen birth cohorts (5-year intervals from pre-1916 to 1985). Time spent in three categories of LTPA was determined and metabolic equivalent (MET) values of 3.3, 4.0 and 8.0 were assigned for walking, moderate and vigorous activities, respectively, to calculate daily volume (MET minutes). Energy expended in LTPA was calculated using estimated BMR (from self-reported weight and published formulae), multiplied by the MET value. Regression models were fitted to the data. Age and period had independent effects on duration, volume and energy expenditure of LTPA for both males (P<0.01) and females (P<0.01), while birth cohort had independent effects for males only such that all three LTPA factors declined with recency of birth cohort (P<0.01). This indicates that more recent birth cohorts of males may need to be targeted to increase LTPA, but as duration, volume and energy expended in leisure time have been declining since 1990, both the sexes may benefit from the promotion of increased LTPA.     

Twenty-year trends in physical activity among Canadian adults

OBJECTIVE: Physical inactivity is associated with increased risk of mortality and chronic diseases, yet trend information is lacking in most countries. This investigation examines physical activity levels of Canadian adults aged 18 years and older. METHODS: Data were collected in six national surveys between 1981 and 2000. Sample sizes ranged from 2,500 to 18,000. Prevalences were tested using Chi-square and Student's t-tests. Socio-demographic correlates were examined using odds ratios adjusted for age, sex, education and income. RESULTS: Physical activity increased in the 1980s and 1990s among men and women and for all age, education and income groups (p<0.01). Although education differentials narrowed over the period, age differentials widened and income differentials emerged. DISCUSSION: The positive trend in Canada is consistent with Finland, but contrary to recent trends for Australia, England and the United States. Despite increases, sedentary living remains a public health issue particularly among women, older adults and lower income groups.     

Social class differences in health until the age of seven years among the Finnish 1987 birth cohort

Studies on social class differences in childhood health are controversial partly because of different data collection methods, limited sample sizes and the use of limited numbers of health indicators. The increasing collection of health register data enables the use of such data in social class studies. Our purpose was to investigate social class differences in mortality and morbidity among all children born in Finland in 1987 (N=59,865 liveborns) until the age of seven by using several national health registers, and to study whether perinatal health explains these differences. The follow-up was based on data linkage with six national health registers, with 18 regional registers of mentally disabled children, covering the whole country, and with 38 educational registers of the largest county. Morbidity was measured in terms of a cumulative disease index, the cumulative incidence of asthma, diabetes, epilepsy and intellectual disability, hospitalisations, disease-related welfare benefits and special education. Social class, divided in four groups (I–III, Others) was defined by using the mother's occupation at the time the child was seven years old. Our study showed that register-based data collection is a feasible method for studying social class differences in health. In the unadjusted analysis, social class differences were found for all indicators except mortality after the age of one year and for the cumulative incidence of asthma and diabetes. After adjusting for confounders, the children in the lowest social class had the highest risk for poor health outcome both in the perinatal period and in childhood, and had the most intellectual disabilities, the highest mean of hospitalisation days, and received the most special education. The differences were not explained by perinatal health. The health of the children in the lowest social class was poorer, especially regarding mental indicators.     

The longitudinal age and birth cohort trends of smoking in Sweden: a 24-year follow-up study

Objectives

The aim of this study is to analyse longitudinally, the annual effects of age group and birth cohort on smoking in the Swedish population during a 24-year period and to analyse the smoking trends for different levels of education.

Methods

A random sample of adult, non-institutionalized persons aged 16–71 years was interviewed every 8 years by professional interviewers. In addition to three time-related variables—year of interview, age at the time of the interview, and year of birth—we included the following explanatory variables in the analyses: sex, educational level, and urbanization.

Results

We found significant decreases in smoking prevalence in all studied subgroups. The adjusted odds ratios for age were 0.89 (95 % CI 0.88–0.90) and 0.92 (95 % CI 0.91–0.93) for men and women, respectively. The decreases in smoking over time were significant in all levels of education, except for in women with low educational level.

Conclusions

In Sweden, the prevalence of smoking has decreased in most age groups and cohorts, and in persons in most levels of education, albeit less so in women with low educational level.     

Social class across the life course and physical activity at age 34 years in the 1970 British birth cohort

PurposeTo examine the associations between social class at ages 0, 5, 10, 30, and 34 years and physical activity at age 34 years using a novel approach to analysis of life course data.MethodsWe used structural equation modeling to compare three competing models in life course epidemiology: the accumulation of risk model with additive effects, the accumulation of risk model with trigger effect, and the critical period model. Data were from a nationally representative prospective cohort of 16,571 British men and women born in 1970. Outcomes were physical activity during leisure time, during transports, and at work.ResultsFor all three domains of physical activity, for men and women, the accumulation of risk model with additive effects fit the data best. In this model, social class at ages 0, 5, 10, 30, and 34 years were associated with physical activity at age 34 years, although the magnitude and the direction of the associations for social class at each age varied by physical activity outcome and by sex.ConclusionsStructural equation modeling appears to be a helpful tool in selecting among competing models in life course epidemiology.     

Associations between physical activity,sedentary time,sleep duration and daytime sleepiness in US adults

ObjectiveTo examine the associations between objectively measured physical activity (PA) or sedentary behavior and self-reported sleep duration or daytime sleepiness in a nationally representative sample of healthy US adults (N = 2128).MethodsWe report analyses of four aspects of sedentary behavior and PA derived from accelerometry data (minutes of sedentary time, activity counts/minute, Minutes of Moderate and Vigorous PA [MVPA], and MVPA in 10-minute bouts) versus self-report of sleep duration and frequency of daytime sleepiness from the 2005–2006 National Health and Nutrition Examination Survey.ResultsAge and sex dependence of associations between PA and sleep were observed. Aspects of PA were significantly lower in adults reporting more frequent daytime sleepiness in younger (20–39) and older (≥ 60) age groups, but not in middle-aged (40–59), respondents. In younger respondents, PA increased with sleep duration, but in middle aged and older respondents PA was either unrelated to sleep duration or lower in those reporting ≥ 8 h of sleep. Objectively measured sedentary time showed limited evidence of associations with sleep duration.ConclusionsFurther research delineating the relationships between sleep and PA is important because both activities have been implicated in diverse health outcomes as well as in the etiology of obesity.     

The association of daily physical activity and birth outcome: a population-based cohort study

The potential relationship between daily physical activity and pregnancy outcome remains unclear because of the wide variation in study designs and physical activity assessment measures. We sought to prospectively quantify the potential effects of the various domains of physical activity on selected birth outcomes in a large unselected population. The sample consisted of 11,759 singleton pregnancies from the Avon longitudinal study of parents and children, United Kingdom. Information on daily physical activity was collected by postal questionnaire for self-report measures. Main outcome measures were birth weight, gestational age at delivery, preterm birth and survival. After controlling for confounders, a sedentary lifestyle and paid work during the second trimester of pregnancy were found to be associated with a lower birth weight, while ‘bending and stooping’ and ‘working night shifts’ were associated with a higher birth weight. There was no association between physical exertion and duration of gestation or survival. Repetitive boring tasks during the first trimester was weakly associated with an increased risk of preterm birth (<37 weeks) (adjusted odds ratio [OR] = 1.25, 95% CI 1.04–1.50). ‘Bending and stooping’ during the third trimester was associated with a reduced risk of preterm birth (adjusted OR = 0.73, 95% CI 0.63–0.84). Demanding physical activities do not have a harmful effect on the selected birth outcomes while a sedentary lifestyle is associated with a lower birth weight. In the absence of either medical or obstetric complications, pregnant women may safely continue their normal daily physical activities should they wish to do so.     

Measures of placental growth in relation to birth weight and gestational age

Fetal growth depends in part on placental growth. The authors tested placental measures derived from digital images for reliability and to evaluate their association with birth weight and gestational age. A total of 628 women recruited into the Pregnancy, Infection, and Nutrition Study, a prospective cohort study of preterm birth in central North Carolina between 2002 and 2004, delivered singleton liveborn infants after 24 completed weeks' gestation. Novel chorionic plate morphometric parameters captured off digital images of the gross placenta were analyzed as estimators of gestational age and birth weight. Without acknowledgment to placental weight, digitally obtained lateral chorionic plate growth measures accounted for 17 percent of gestational age variance and 35 percent of birth weight variance, overall. Chorionic plate measures accounted for 10 percent of birth weight variance beyond that accounted for by placental weight alone. Among preterm births, 34 percent of gestational age variance and 63 percent of birth weight variance were accounted for by lateral chorionic plate growth measures. Intraclass correlation coefficients for the novel digital measures ranged from 0.96 to 0.98. Reliable digital measures of lateral chorionic plate growth estimate birth weight variance more strongly than gestational age, project variance that is not accounted for by placental weight, and project these outcomes to a greater degree in preterm births than at term.     

Regional equity in childhood health--register-based follow-up of the Finnish 1987 birth cohort

Our objective was to investigate regional health differences among Finnish children using a population-based longitudinal register data. All live births born in 1987 were included in the study (N=59,546) and followed-up until the age of seven years. Statistically significant regional variation was found for all health indicators but diabetes. Background variables, such as maternal age and social class, explained only the difference in mortality. Various indicators gave different geographical patterns. Regional equity in childhood health has not been achieved in Finland. Existing health registers were feasible in studying regional variation in health, but a set of comprehensive morbidity indicators - preferably derived from different data sources - should be developed to monitor equity in health.     

Infancy and childhood growth and physical activity in adolescence: prospective birth cohort study from Brazil

Background

A poor understanding of the specific lifestyle behaviors that result in weight loss has hindered the development of effective interventions. The aim of this paper was to identify potential behavioral mediators of weight loss in the Healthy Dads, Healthy Kids (HDHK) intervention for overweight fathers.

Findings

The three-month intervention was evaluated in a randomized controlled trial and conducted in Newcastle, New South Wales, Australia. Baseline, three month (immediate post-intervention) and six month assessments were conducted. Recruitment and follow-up occurred between October 2008 and May 2009. The study sample included 53 overweight/obese men [mean ( SD) age=40.6( 97.1) years; body mass index (BMI)=33.2 (3.9) kgm^-2] and their primary school-aged children [n=71, 54% boys; age=8.2 (2.0) years] who were randomized to HDHK program or a wait-list control group. Physical activity (PA) was assessed using pedometers and dietary behaviors were measured using a validated food frequency questionnaire. The intervention resulted in significant weight loss (5.131.27kg, P<0.0001) and increased PA among fathers (2769750 steps/day, P<0.001) and their children (1486521 steps/day, P<0.01). Fathers PA mediated weight loss in the intervention (AB=2.31, 95% CI=4.63 to 0.67) and was responsible for 47% of the intervention effect. Changes in dietary behaviors were not statistically significant.

Conclusions

PA was an important mediator of weight loss in the HDHK intervention. Encouraging overweight fathers to be more active with their children appears to be a promising strategy for obesity treatment in men.     

Recreational physical activity and sedentary behavior in relation to ovarian cancer risk in a large cohort of US women

Factors that influence circulating sex hormones, such as physical activity, have been proposed to influence ovarian cancer risk; however, results from previous epidemiologic studies have been inconsistent. The authors examined the association among physical activity, sedentary behavior, and ovarian cancer risk in the American Cancer Society Cancer Prevention Study II Nutrition Cohort, a prospective study of cancer incidence and mortality, using information obtained at baseline in 1992. From 1992 to 2001, 314 incident ovarian cancer cases were identified among 59,695 postmenopausal women who were cancer free at enrollment. Cox proportional hazards modeling was used to compute hazard rate ratios while adjusting for potential confounders. No overall association was observed between measures of past physical activity or with recreational physical activity at baseline and risk of ovarian cancer in this study (for the highest category of physical activity compared with none: hazard rate ratio = 0.73, 95% confidence interval: 0.40, 1.34). However, a prolonged duration of sedentary behavior was associated with an increased risk (for > or = 6 vs. < 3 hours per day: hazard rate ratio = 1.55, 95% confidence interval: 1.08, 2.22; p(trend) = 0.01). Results from this study suggest that high levels of sedentary behavior may increase the risk of ovarian cancer, but they do not support a major impact of light and moderate physical activity on ovarian cancer risk.     

Mortality of young adults in relation to single-parent family background. A prospective study of the northern Finland 1966 birth cohort

BACKGROUND: The relationship between family background and mortality of offspring was studied by using a prospectively collected, general population, birth cohort database (n = 11,017), that is the Northern Finland 1966 birth cohort which is linked with the national death register. METHODS: A logistic regression analysis was performed in order to examine the association between family background and death of offspring (between ages 16 and 28 years). RESULTS: It was revealed that 117 subjects (90 males and 27 females) from the original birth cohort had died. The majority of the deaths were due to unnatural causes in both sexes (79%). After adjusting for confounders (psychiatric diagnosis and parental social class), the results indicated that the general mortality risk for males with a single-parent family background was significantly increased compared with males from a two-parent family background (odds ratio 1.8 and 95% confidence interval: 1.1-2.9). The risk of committing suicide was significantly increased among young adult males with a single-parent family background (OR 2.5 and 95% CI: 1.1-5.8). CONCLUSION: Our finding calls for health care professionals to provide more preventative mental health support for children and adolescents living in broken homes.