A life course approach to balance ability

Balance ability is a crucial component of everyday life, underlying physical movement at all stages in life. Despite this, balance is an overlooked aspect of physical health and ageing, with minimal evidence of how factors throughout life are associated with balance ability. This PhD thesis used a life course approach to investigate how factors across life contribute to standing balance in mid and later life, and to examine associations between balance ability and subsequent falls risk. Data from the MRC National Survey of Health and Development (NSHD) were used. NSHD is a nationally representative sample of 5362 males and females, born in England, Scotland and Wales in March 1946 and followed up to 24 times across life. One-legged balance time with eyes closed was assessed at ages 53, 60-64 and 69 (n=3111 individuals with a balance time at one or more age). Analytical methods included multilevel models, structural equation models, linear and logistic regressions and receiver-operating characteristic analyses. In adulthood, disadvantaged socioeconomic position, poor health and adverse health related behaviours were associated with poorer balance ability (Chapter 3). In childhood, disadvantaged socioeconomic position, lower cognitive ability, slower coordination and early or late attainment of motor milestones were associated with poorer balance ability (Chapter 3, 4). Across several domains, higher cognitive ability in midlife was associated with better balance ability (Chapter 5). The association between verbal memory and subsequent balance ability was unidirectional, with some evidence of more complex bidirectional associations with search speed (Chapter 6). Most factors across life demonstrated changing patterns of association with balance with age. Finally, balance ability was associated with subsequent falls, although the one-legged stand did not appear to be a sensitive prognostic indicator of fall risk (Chapter 7). Better understanding of the socioeconomic, cognitive, behavioural and health pathways across life which relate to subsequent balance ability, identified in this thesis, provides an opportunity to intervene earlier in life to minimise, prevent or delay balance impairment or decline

Associations Between Adolescent Sport and Exercise Participation and Device-Assessed Physical Activity in Adulthood: Evidence From the 1970 British Cohort Study

BACKGROUND: Adolescence is a critical period filled with life changes. Early implementation of effective health promotion strategies could help alleviate the morbidity and mortality associated with inactivity. This study investigated whether adolescent participation in exercise and sport is associated with device-assessed physical activity (PA) levels in midlife. METHODS: A total of 2984 participants (41.2% male) from the 1970 British Cohort Study were included. Participants were surveyed at age 16 years on 5 indicators of exercise and sport participation. Total daily PA and moderate to vigorous PA (MVPA) at age 46 years were measured using a thigh-worn accelerometer, worn for 7 days. Associations between each adolescent exercise or sport indicator and adulthood total daily PA and MVPA were examined using linear regressions, adjusting for sex, wear time, body mass index, smoking, disability, malaise, alcohol consumption, social class, education, and self-rated health. RESULTS: In fully adjusted models, adolescents who reported exercising "much more" than others (8.6 min/d; 95% confidence interval, -0.1 to 17.1), who played sports at the park/playground more than once a week (8.5 [3.0-14.0] min/d), and who exercised on the most recent Saturday (3.8 [0.7-6.9] min/d) had higher adult total PA levels than those who reported the lowest activity levels. There was no evidence of an association between greater sport and exercise participation at age 16 y and MVPA at age 46 y. There was no association between sports at school and either measure of adult PA. CONCLUSION: Active adolescents, particularly those who engaged in out-of-school exercise, had higher total daily PA levels, but not MVPA levels, in midlife. This highlights the potential of early PA interventions to improve PA levels in adulthood

Dose-response association between step count and cardiovascular disease risk markers in middle aged adults

Several step-based daily targets have been widely circulated, but there is a lack of empirical population-based evidence to support such guidance. We examined dose-response associations between step count and classical CVD risk markers (glycated haemoglobin, high density lipoprotein cholesterol, triglycerides, C-reactive protein) in 4,665 adults (aged 46 yr; 51.4% female) in a cross-sectional study. Step counts were measured from a thigh mounted accelerometer (activPAL) worn over 7 days. The shape of the dose response curve for most risk markers was 'L-shaped', with linear risk reduction up to around 10,000 steps a day. Controlling for stepping intensity did not materially alter our results

Does moderate to vigorous physical activity mediate the association between depression and physical function in midlife: Evidence from two British birth cohort studies

BACKGROUND: Mental health and physical health are intrinsically linked, yet the mechanisms are not well understood. We investigated whether moderate-vigorous physical activity (MVPA) mediated the association between depression and physical function (PF) in midlife. METHODS: Individuals from two UK birth cohorts born within one week in 1958 (n = 7278) and 1970 (n = 6097) with data on depression (ages 33/34; Malaise Inventory), MVPA (age 42; self-reported) and PF (Short Form-36 subscale). Covariates included sex, childhood and adulthood social class, maternal mental health, childhood mood, alcohol consumption, smoking habits, sleep, marital status, BMI and long-standing illness/disability. Linear or multinomial logistic regression models examined associations between depression, MVPA and PF. We used a parametric g-computation mediation analysis approach to estimate percent differences in PF. RESULTS: Depression was associated with less frequent MVPA and poorer PF. Lower MVPA was associated with worse PF. The direct effect - randomised analogue not operating via MVPA - of depression on PF was -18.8 % (95%CI:--25.8,-11.8) and -15.8 % (20.6,-11.0) in the 1958 and 1970 cohorts, respectively. The indirect effect -operating via MVPA - was -0.5 % (-1.0,-0.03) and -0.2 % (-0.6, 0.3), resulting in a total proportion mediated of 3.1 % (0.1, 6.0) and 0.9 % (-1.6, 3.4). LIMITATIONS: MVPA was self-reported. Intermediate confounders and mediators were measured at the same age, however associations did not change in sensitivity analysis considering age 46 MVPA (1958 cohort). CONCLUSIONS: Although higher MVPA was protective against poor PF, there was only minor evidence that it mediated the association between depression and PF. Further investigation into other potential mediators of pathways from mental to physical health is needed

Injury incidence, severity and type across the menstrual cycle in female footballers:A prospective three season cohort study

AbstractPurpose The aim of the study was to assess the influence of menstrual cycle phase on injury incidence, severity and type in elite female professional footballers over three seasons.Methods Time-loss injuries and menstrual cycle data were prospectively recorded for 26 elite female football players across three seasons. The menstrual cycle was categorised into four phases using a standardised model: menstruation (phase 1; P1), remainder of follicular phase (phase 2; P2), early luteal (phase 3; P3), and pre-menstrual phase (phase 4; P4). Injury incidence rates (IRR) and ratios (IIRR) were calculated for overall injuries, injury severity, type, contact vs non-contact and game/training.Results 593 cycles across 13,390 days were tracked during the study and 74 injuries from 26 players were eligible for analysis. When comparing IRR between phases (reference: P1), overall injury rates were highest in P4 (IIRR: 2.30 [95% CI: 0.99-5.34; p = 0.05]). When examining rates by injury severity and type, IRR were also highest in P4 for ≤7 days’ time-loss (4.40 [0.93-20.76; p = 0.06]), muscle-specific (6.07 [1.34-27.43; p = 0.02]) and non-contact (3.05 [1.10-8.50; p = 0.03]) injuries. Muscle-specific (IIRR P3:P1: 5.07 [1.16-22.07; p = 0.03]) and ≤ 7 days’ time-loss (4.47 [1.01-19.68; p = 0.05]) injury risk was also significantly higher in P3. Muscle injuries were the most prevalent sub-type (n = 41). No anterior cruciate ligament injuries were recorded across the monitoring period.Conclusions Injury risk was significantly elevated during the luteal phase of the menstrual cycle (P3 and P4) among elite female professional footballers. Further research is urgently needed to better understand the influence of the menstrual cycle on injury risk and to develop interventions to mitigate risk

Fractal complexity of daily physical activity and cognitive function in a midlife cohort

High stability of fluctuation in physiological patterns across fixed time periods suggest healthy fractal complexity, while greater randomness in fluctuation patterns may indicate underlying disease processes. The importance of fractal stability in mid-life remains unexplored. We quantified fractal regulation patterns in 24-h accelerometer data and examined associations with cognitive function in midlife. Data from 5097 individuals (aged 46) from the 1970 British Cohort Study were analyzed. Participants wore thigh-mounted accelerometers for seven days and completed cognitive tests (verbal fluency, memory, processing speed; derived composite z-score). Detrended fluctuation analysis (DFA) was used to examine temporal correlations of acceleration magnitude across 25 time scales (range: 1 min-10 h). Linear regression examined associations between DFA scaling exponents (DFAe) and each standardised cognitive outcome. DFAe was normally distributed (mean ± SD: 0.90 ± 0.06; range: 0.72-1.25). In males, a 0.10 increase in DFAe was associated with a 0.30 (95% Confidence Interval: 0.14, 0.47) increase in composite cognitive z-score in unadjusted models; associations were strongest for verbal fluency (0.10 [0.04, 0.16]). Associations remained in fully-adjusted models for verbal fluency only (0.06 [0.00, 0.12]). There was no association between DFA and cognition in females. Greater fractal stability in men was associated with better cognitive function. This could indicate mechanisms through which fractal complexity may scale up to and contribute to cognitive clinical endpoints

Prenatal and postnatal correlates of moderate-to-vigorous physical activity in midlife: evidence from the 1970 British Cohort Study

Background: It is hypothesised that lifelong physical activity behaviours are established in early life, however there is minimal, and contradictory, evidence examining prenatal and postnatal factors in relation to adulthood physical activity. We investigated associations between prospectively ascertained prenatal/postnatal factors and device-measured moderate-to-vigorous physical activity (MVPA) in midlife. Methods Analyses included 5011 participants from the 1970 British Cohort Study, a birth cohort study of individuals born within the same week. At birth, the following factors were ascertained: socioeconomic position (SEP), maternal age, number of previous pregnancies, maternal smoking, maternal diabetes, gestational age, birth weight, breastfeeding status and infant health concerns. MVPA was captured at age 46 with a thigh-worn accelerometer device following a 24-hour protocol over 7 days. / Results: In sex-adjusted models, lower SEP (−6.7 min/day (95% CI: −9.0 to –4.4) in those with a partly or unskilled paternal occupation), younger maternal age (0.4 min/day (0.2 to 0.5) per additional year of maternal age), maternal smoking during pregnancy (−2.5 min/day (−4.0 to –1.0)) and post-term gestational age (−7.4 min/day (−11.5 to –3.4); boys only) were associated with lower MVPA at age 46. In the mutually adjusted model, associations did not change but there was some evidence that birth weight may also be associated with MVPA levels. / Conclusions: SEP, maternal age, maternal smoking, post-term birth in boys and birth weight were associated with MVPA in midlife, indicating that midlife physical activity behaviours may be partially established at birth. Early interventions in disadvantaged environments may have a positive impact on physical activity throughout the life course

Developmental factors associated with decline in grip strength from midlife to old age: a British birth cohort study

Objectives To test whether developmental factors are associated with grip strength trajectories between 53 and 69 years, and operate independently or on the same pathway/s as adult factors. Design British birth cohort study. Setting England, Scotland and Wales. Participants 3058 men and women. Main outcome measures Grip strength (kg) at ages 53, 60–64 and 69 were analysed using multilevel models to estimate associations with developmental factors (birth weight, growth parameters, motor and cognitive development) and father’s social class, and investigate adult factors that could explain observed associations, testing for age and sex interactions. Results In men, heavier birth weight, beginning to walk ‘on time’, later puberty and greater weight 0–26 years and in women, heavier birth weight and earlier age at first standing were independently associated with stronger grip but not with its decline. The slower decline in grip strength (by 0.07 kg/year, 95% CI 0.02 to 0.11 per 1 SD, p=0.003) in men of higher cognitive ability was attenuated by adjusting for adult verbal memory. Conclusions Patterns of growth and motor development have persisting associations with grip strength between midlife and old age. The strengthening associations with cognition suggest that, at older ages, grip strength increasingly reflects neural ageing processes. Interventions across life that promote muscle development or maintain muscle strength should increase the chance of an independent old age.

Blood glucose variance measured by continuous glucose monitors across the menstrual cycle

Past studies on how blood glucose levels vary across the menstrual cycle have largely shown inconsistent results based on limited blood draws. In this study, 49 individuals wore a Dexcom G6 continuous glucose monitor and a Fitbit Sense smartwatch while measuring their menstrual hormones and self-reporting characteristics of their menstrual cycles daily. The average duration of participation was 79.3 ± 21.2 days, leading to a total of 149 cycles and 554 phases in our dataset. We use periodic restricted cubic splines to evaluate the relationship between blood glucose and the menstrual cycle, after which we assess phase-based changes in daily median glucose level and associated physiological parameters using mixed-effects models. Results indicate that daily median glucose levels increase and decrease in a biphasic pattern, with maximum levels occurring during the luteal phase and minimum levels occurring during the late-follicular phase. These trends are robust to adjustments for participant characteristics (e.g., age, BMI, weight) and self-reported menstrual experiences (e.g., food cravings, bloating, fatigue). We identify negative associations between each of daily estrogen level, step count, and low degrees of fatigue with higher median glucose levels. Conversely, we find positive associations between higher food cravings and higher median glucose levels. This study suggests that blood glucose could be an important parameter for understanding menstrual health, prompting further investigation into how the menstrual cycle influences glucose fluctuation

Associations of word memory, verbal fluency, processing speed and crystallised cognitive ability with one-legged balance performance in mid and later life

Background Cognitive integration of sensory input and motor output plays an important role in balance. Despite this, it is not clear if specific cognitive processes are associated with balance and how these associations change with age. We examined longitudinal associations of word memory, verbal fluency, search speed and reading ability with repeated measures of one-legged balance performance. Methods Up to 2934 participants in the MRC National Survey of Health and Development, a British birth cohort study, were included. At age 53, word memory, verbal fluency, search speed and reading ability were assessed. One-legged balance times (eyes closed) were measured at ages 53, 60-64 and 69 years. Associations between each cognitive measure and balance time were assessed using random-effects models. Adjustments were made for sex, death, attrition, height, body mass index, health conditions, health behaviours, education, and occupational class. Results In sex-adjusted models, one SD higher scores in word memory, search speed and verbal fluency were associated with 14.1% (95%CI: 11.3,16.8), 7.2% (4.4,9.9) and 10.3% (7.5,13.0) better balance times at age 53, respectively. Higher reading scores were associated with better balance, although this association plateaued. Associations were partially attenuated in mutually-adjusted models and effect sizes were smaller at ages 60-64 and 69. In fully-adjusted models, associations were largely explained by education, although remained for word memory and search speed. Conclusions Higher cognitive performance across all measures was independently associated with better balance performance in midlife. Identification of individual cognitive mechanisms involved in balance could lead to opportunities for targeted interventions in midlife