David Bann

Gender and telomere length: Systematic review and meta-analysis

BACKGROUND It is widely believed that females have longer telomeres than males, although results from studies have been contradictory. METHODS We carried out a systematic review and meta-analyses to test the hypothesis that in humans, females have longer telomeres than males and that this association becomes stronger with increasing age. Searches were conducted in EMBASE and MEDLINE (by November 2009) and additional datasets were obtained from study investigators. Eligible observational studies measured telomeres for both females and males of any age, had a minimum sample size of 100 and included participants not part of a diseased group. We calculated summary estimates using random-effects meta-analyses. Heterogeneity between studies was investigated using sub-group analysis and meta-regression. RESULTS Meta-analyses from 36 cohorts (36,230 participants) showed that on average females had longer telomeres than males (standardised difference in telomere length between females and males 0.090, 95% CI 0.015, 0.166; age-adjusted). There was little evidence that these associations varied by age group (p=1.00) or cell type (p=0.29). However, the size of this difference did vary by measurement methods, with only Southern blot but neither real-time PCR nor Flow-FISH showing a significant difference. This difference was not associated with random measurement error. CONCLUSIONS Telomere length is longer in females than males, although this difference was not universally found in studies that did not use Southern blot methods. Further research on explanations for the methodological differences is required.

Light Intensity physical activity and sedentary behavior in relation to body mass index and grip strength in older adults: cross-sectional findings from the Lifestyle Interventions and Independence for Elders (LIFE) study.

Background Identifying modifiable determinants of fat mass and muscle strength in older adults is important given their impact on physical functioning and health. Light intensity physical activity and sedentary behavior are potential determinants, but their relations to these outcomes are poorly understood. We evaluated associations of light intensity physical activity and sedentary time—assessed both objectively and by self-report—with body mass index (BMI) and grip strength in a large sample of older adults. Methods We used cross-sectional baseline data from 1130 participants of the Lifestyle Interventions and Independence for Elders (LIFE) study, a community-dwelling sample of relatively sedentary older adults (70-89 years) at heightened risk of mobility disability. Time spent sedentary and in light intensity activity were assessed using an accelerometer worn for 3–7 days (Actigraph GT3X) and by self-report. Associations between these exposures and measured BMI and grip strength were evaluated using linear regression. Results Greater time spent in light intensity activity and lower sedentary times were both associated with lower BMI. This was evident using objective measures of lower-light intensity, and both objective and self-reported measures of higher-light intensity activity. Time spent watching television was positively associated with BMI, while reading and computer use were not. Greater time spent in higher but not lower intensities of light activity (assessed objectively) was associated with greater grip strength in men but not women, while neither objectively assessed nor self-reported sedentary time was associated with grip strength. Conclusions In this cross-sectional study, greater time spent in light intensity activity and lower sedentary times were associated with lower BMI. These results are consistent with the hypothesis that replacing sedentary activities with light intensity activities could lead to lower BMI levels and obesity prevalence among the population of older adults. However, longitudinal and experimental studies are needed to strengthen causal inferences.

Physical Activity Across Adulthood in Relation to Fat and Lean Body Mass in Early Old Age: Findings From the Medical Research Council National Survey of Health and Development, 1946–2010

Fat and lean body mass have important implications for health and physical functioning in older age, and physical activity is purported to be an important modifiable determinant. However, our evidence-based understanding of its role is limited. We examined the associations of physical activity, assessed both by self-report (using data on leisure time physical activity (LTPA) collected on 4 occasions over a 28-year period) and objectively (using 5-day heart rate and movement monitoring), with fat and lean mass at ages 60–64 years in 1,162 British participants from the Medical Research Council National Survey of Health and Development in 1946–2010. Higher objectively assessed physical activity energy expenditure (PAEE) at ages 60–64 years was associated with lower fat mass and android (abdominal):gynoid (hip) fat ratio (mean differences in fat mass per 1–standard deviation increase in PAEE were −0.79 kg/m1.2 in men (95% confidence interval: −1.08, −0.50) and −1.79 kg/m1.2 (95% confidence interval: −2.15, −1.42) in women). After adjustment for fat mass, higher PAEE was associated with higher appendicular lean mass. Both light and moderate-to-vigorous intensities of activity were associated with fat mass, and the latter was associated with lean mass. More frequent LTPA across adulthood was associated with lower fat mass (in women only) and higher appendicular lean mass (in both sexes, after adjustment for fat mass). These results support the promotion of LTPA across adulthood, as well as both light and moderate-to-vigorous intensities of activity among older adults.

Birth weight and growth from infancy to late adolescence in relation to fat and lean mass in early old age: findings from the MRC National Survey of Health and Development

Objective:High birth weight and greater weight gain in infancy have been associated with increased risk of obesity as assessed using body mass index, but few studies have examined associations with direct measures of fat and lean mass. This study examined associations of birth weight and weight and height gain in infancy, childhood and adolescence with fat and lean mass in early old age.Subjects:A total of 746 men and 812 women in England, Scotland and Wales from the MRC National Survey of Health and Development whose heights and weights had been prospectively ascertained across childhood and adolescence and who had dual energy X-ray absorptiometry measures at age 60–64 years.Methods:Associations of birth weight and standardised weight and height (0–2 (weight only), 2–4, 4–7, 7–11, 11–15, 15–20 years) gain velocities with outcome measures were examined.Results:Higher birth weight was associated with higher lean mass and lower android/gynoid ratio at age 60–64 years. For example, the mean difference in lean mass per 1 standard deviation increase in birth weight was 1.54 kg in males (95% confidence interval=1.04, 2.03) and 0.78 kg in females (0.41, 1.14). Greater weight gain in infancy was associated with higher lean mass, whereas greater gains in weight in later childhood and adolescence were associated with higher fat and lean mass, and fat/lean and android/gynoid ratios. Across growth intervals greater height gain was associated with higher lean but not fat mass, and with lower fat/lean and android/gynoid ratios.Conclusion:Findings suggest that growth in early life may have lasting effects on fat and lean mass. Greater weight gain before birth and in infancy may be beneficial by leading to higher lean mass, whereas greater weight gain in later childhood and adolescence may be detrimental by leading to higher fat/lean and android/gynoid ratios.

“Skeletal Muscle Function Deficit” in A Nationally Representative British Birth Cohort in Early Old Age

Background. Recommendations for identifying age-related muscle dysfunction have recently been published. We aimed to compare definitions for clinically relevant weakness and low lean mass proposed by the Foundation for the National Institutes of Health (FNIH) Sarcopenia project with the definition of sarcopenia proposed by the European Working Group on Sarcopenia in Older People (EWGSOP). Methods. A total of 1566 men and women from a British birth cohort had measures of appendicular lean mass, grip strength and timed up, and go speed at ages 60–64. Prevalence of low lean mass, weakness and slowness, identified using the FNIH and EWGSOP recommendations were estimated and compared: using kappa statistics and; by testing cross-sectional associations of both definitions of low lean mass and weakness with slowness and self-reported difficulties walking. Results. The combined prevalence of low lean mass and weakness ranged from 1.1% in men using FNIH criteria to 6.4% in women using EWGSOP criteria. There was limited overlap between the groups identified using the different criteria, driven by limited agreement between the two definitions of low lean mass. Using FNIH criteria, both low lean mass and weakness were associated with higher odds of slowness and difficulties walking; whereas low lean mass classified using EWGSOP criteria was not associated with these markers of mobility impairment. Conclusions. At relatively young ages, signs of skeletal muscle function deficit with potential clinical relevance are already identifiable in the general population. This suggests that implementation of strategies to prevent mobility limitations, related to age-related muscle dysfunction, may need to start at least as early as midlife.

Childhood socioeconomic position and adult leisure-time physical activity: a systematic review

Regular leisure-time physical activity (LTPA) benefits health and is thought to be less prevalent in lower socioeconomic groups. Evidence suggests that childhood socioeconomic circumstances can impact on adult health and behaviour however, it is unclear if this includes an influence on adult LTPA. This review tested the hypothesis that a lower childhood socioeconomic position (SEP) is associated with less frequent LTPA during adulthood. Studies were located through a systematic search of MEDLINE, Embase, PsycINFO, CINAHL and SPORTDiscus and by searching reference lists. Eligible studies were English-language publications testing the association between any indicator of childhood SEP and an LTPA outcome measured during adulthood. Forty-five papers from 36 studies, most of which were European, were included. In most samples, childhood SEP and LTPA were self-reported in midlife. Twenty-two studies found evidence to support the review’s hypothesis and thirteen studies found no association. Accounting for own adult SEP partly attenuated associations. There was more evidence of an association in British compared with Scandinavian cohorts and in women compared with men. Results did not vary by childhood SEP indicator or age at assessment of LTPA. This review found evidence of an association between less advantaged childhood SEP and less frequent LTPA during adulthood. Understanding how associations vary by gender and place could provide insights into underlying pathways.

Socioeconomic position across life and body composition in early old age: findings from a British birth cohort study

Background Previous studies have reported associations between lower lifetime socioeconomic position (SEP) and higher body mass index in adulthood, but few have examined associations with direct measures of fat and lean mass which are likely to have independent roles in health and physical functioning. Methods We examined associations of SEP across life with dual-energy X-ray absorptiometry measures of fat and lean mass at 60–64 years using data from a total of 1558 men and women participating in the Medical Research Council (MRC) National Survey of Health and Development. We also examined whether associations of childhood SEP with fat and lean mass were explained by preadulthood weight gain (birth weight, 0–7 and 7–20 years) and adult SEP. Results Lower SEP across life was associated with higher fat mass and higher android to gynoid fat mass ratio. For example, the mean difference in fat mass index comparing the lowest with the highest paternal occupational class at 4 years (slope index of inequality) was 1.04 kg/m1.2 in men (95% CI 0.09 to 1.99) and 2.61 in women (1.34 to 3.89), equivalent to a 8.6% and 16.1% difference, respectively. After adjustment for fat mass, lower SEP across life was associated with lower lean mass in women, while only contemporaneous household income was associated in men. Associations between childhood SEP and outcomes were partly explained by preadulthood weight gain and adult SEP. Conclusions This study identified lifetime socioeconomic patterning of fat and lean mass in early old age. This is likely to have important implications and may partly explain socioeconomic inequalities in health and physical functioning.

Body Mass Index From Age 15 Years Onwards and Muscle Mass, Strength, and Quality in Early Old Age: Findings From the MRC National Survey of Health and Development

Background. As more people live more of their lives obese, it is unclear what impact this will have on muscle mass, strength, and quality. We aimed to examine the associations of body mass index (BMI) from age 15 years onwards with low muscle mass, strength, and quality in early old age. Methods. A total of 1,511 men and women from a British birth cohort study with BMI measured at 15, 20, 26, 36, 43, 53, and 60–64 years and dual-energy x-ray absorptiometry scans at 60–64 years were included. Four binary outcomes identified those in the bottom sex-specific 20% of (a) appendicular lean mass (ALM) index (kilogram per square meter), (b) ALM residuals (derived from sex-specific models in which ALM (kilogram) = β0 + β1 height [meter] + β2 fat mass [kilogram]), (c) grip strength (kilogram), (d) muscle quality (grip strength [kilogram]/arm lean mass [kilogram]). Associations of BMI with each outcome were tested. Results. Higher BMI from age 15 years was associated with lower odds of low ALM but higher odds of low muscle quality (per 1 SD increase in BMI at 36 years, odds ratio of low ALM residuals = 0.50 [95% CI: 0.43, 0.59], and muscle quality = 1.50 [1.29, 1.75]). Greater gains in BMI were associated with lower odds of low ALM index but higher odds of low muscle quality. BMI was not associated with grip strength. Conclusions. Given increases in the global prevalence of obesity, cross-cohort comparisons of sarcopenia need to consider our findings that greater gains in BMI are associated with higher muscle mass but not with grip strength and therefore with lower muscle quality.

Birth Weight, School Sports Ability, and Adulthood Leisure-time Physical Activity

Purpose This study aimed to examine the associations of birth weight with ability in school sports in adolescence and participation in leisure-time physical activity (LTPA) across adulthood and to investigate whether associations between birth weight and LTPA change with age. Methods Study participants were British singletons born in 1946 and followed up to age 68 yr (the Medical Research Council National Survey of Health and Development). Birth weights were extracted from birth records. Teacher reports of ability in school sports were collected at age 13 yr. LTPA was self-reported at ages 36, 43, 53, 60–64, and 68 yr and categorized at each age as participating in sports, exercise, and other vigorous LTPA at least once per month versus no participation. Associations were examined using standard and mixed-effects logistic regression models. Results Relevant data were available for 2739 study participants (50.1% female). When compared with the low birth weight group (⩽2.50 kg), those with heavier birth weights were more likely to be rated as above average or average at school sports (vs below average); fully adjusted odds ratio = 1.78 (95% confidence interval = 1.14–2.77). Across adulthood, those with heavier birth weights were more likely to participate in LTPA than those with low birth weight; fully adjusted odds ratio of LTPA across adulthood = 1.52 (95% confidence interval = 1.09–2.14). This association did not vary by age (P = 0.5 for birth weight by age interaction). Conclusions Low birth weight was associated with lower ability in school sports and with nonparticipation in LTPA across adulthood. Identifying the underlying developmental and social processes operating across life for low birth weight infants may inform the design of appropriate interventions to support participation in LTPA across life.

Socioeconomic Inequalities in Body Mass Index across Adulthood: Coordinated Analyses of Individual Participant Data from Three British Birth Cohort Studies Initiated in 1946, 1958 and 1970

Background High body mass index (BMI) is an important contributor to the global burden of ill-health and health inequality. Lower socioeconomic position (SEP) in both childhood and adulthood is associated with higher adult BMI, but how these associations have changed across time is poorly understood. We used longitudinal data to examine how childhood and adult SEP relates to BMI across adulthood in three national British birth cohorts. Methods and Findings The sample comprised up to 22,810 participants with 77,115 BMI observations in the 1946 MRC National Survey of Health and Development (ages 20 to 60–64), the 1958 National Child Development Study (ages 23 to 50), and the 1970 British Cohort Study (ages 26 to 42). Harmonized social class-based SEP data (Registrar General’s Social Class) was ascertained in childhood (father’s class at 10/11 y) and adulthood (42/43 years), and BMI repeatedly across adulthood, spanning 1966 to 2012. Associations between SEP and BMI were examined using linear regression and multilevel models. Lower childhood SEP was associated with higher adult BMI in both genders, and differences were typically larger at older ages and similar in magnitude in each cohort. The strength of association between adult SEP and BMI did not vary with age in any consistent pattern in these cohorts, but were more evident in women than men, and inequalities were larger among women in the 1970 cohort compared with earlier-born cohorts. For example, mean differences in BMI at 42/43 y amongst women in the lowest compared with highest social class were 2.0 kg/m2 (95% CI: −0.1, 4.0) in the 1946 NSHD, 2.3 kg/m2 (1.1, 3.4) in the 1958 NCDS, and 3.9 kg/m2 (2.3, 5.4) the in the 1970 BCS; mean (SD) BMI in the highest and lowest social classes were as follows: 24.9 (0.8) versus 26.8 (0.7) in the 1946 NSHD, 24.2 (0.4) versus 26.5 (0.4) in the 1958 NCDS, and 24.2 (0.3) versus 28.1 (0.8) in the 1970 BCS. Findings did not differ whether using overweight or obesity as an outcome. Limitations of this work include the use of social class as the sole indicator of SEP—while it was available in each cohort in both childhood and adulthood, trends in BMI inequalities may differ according to other dimensions of SEP such as education or income. Although harmonized data were used to aid inferences about birth cohort differences in BMI inequality, differences in other factors may have also contributed to findings—for example, differences in missing data. Conclusions Given these persisting inequalities and their public health implications, new and effective policies to reduce inequalities in adult BMI that tackle inequality with respect to both childhood and adult SEP are urgently required