Ellen Flint

Associations between active commuting, body fat, and body mass index: population based, cross sectional study in the United Kingdom.

Objective To determine if promotion of active modes of travel is an effective strategy for obesity prevention by assessing whether active commuting (walking or cycling for all or part of the journey to work) is independently associated with objectively assessed biological markers of obesity. Design Cross sectional study of data from the wave 2 Health Assessment subsample of Understanding Society, the UK Household Longitudinal Study (UKHLS). The exposure of interest, commuting mode, was self reported and categorised as three categories: private transport, public transport, and active transport. Participants The analytic samples (7534 for body mass index (BMI) analysis, 7424 for percentage body fat analysis) were drawn from the representative subsample of wave 2 respondents of UKHLS who provided health assessment data (n=15 777). Main outcome measures Body mass index (weight (kg)/height (m)2); percentage body fat (measured by electrical impedance). Results Results from multivariate linear regression analyses suggest that, compared with using private transport, commuting by public or active transport modes was significantly and independently predictive of lower BMI for both men and women. In fully adjusted models, men who commuted via public or active modes had BMI scores 1.10 (95% CI 0.53 to 1.67) and 0.97 (0.40 to 1.55) points lower, respectively, than those who used private transport. Women who commuted via public or active modes had BMI scores 0.72 (0.06 to 1.37) and 0.87 (0.36 to 0.87) points lower, respectively, than those using private transport. Results for percentage body fat were similar in terms of magnitude, significance, and direction of effects. Conclusions Men and women who commuted to work by active and public modes of transport had significantly lower BMI and percentage body fat than their counterparts who used private transport. These associations were not attenuated by adjustment for a range of hypothesised confounding factors.

Do labour market status transitions predict changes in psychological well-being?

Background The objective of this study was to establish the direction of causality in the relationship between labour market status and psychological well-being by investigating how transitions between secure employment, insecure employment, unemployment, permanent sickness and other economic inactivity predict changes in psychological well-being over a 16-year period. Method This study used data from the British Household Panel Survey (1991–2007). Psychological well-being was measured using the 12-item General Health Questionnaire (GHQ-12). Fixed effects models were utilised to investigate how transitions between labour market statuses predicted GHQ-12 score, adjusting for current labour market status and a range of covariates. Results After taking account of the contemporaneous effects of joblessness on psychological well-being, and the impact of a range of confounding factors, experiencing a transition from employment to joblessness was significantly predictive of poorer psychological well-being. Transitions into employment were not found to have equal and opposite effects: the positive effects of moving into work from unemployment were not as large as the negative effects of job loss. Transitions between secure and insecure employment did not independently predict changes in psychological well-being. Conclusions A causal relationship between labour market status and psychological well-being is indicated.

Change in commute mode and body-mass index: prospective, longitudinal evidence from UK Biobank

Summary Background Insufficient physical activity is a determinant of obesity and cardiovascular disease. Active travel to work has declined in high-income countries in recent decades. We aimed to determine which socioeconomic and demographic characteristics predicted switching to or from active commuting, whether switching from passive to active commuting (or the reverse) independently predicts change in objectively measured body-mass index (BMI), and to ascertain whether any association is attenuated by socioeconomic, demographic, or behavioural factors. Methods This study used longitudinal data from UK Biobank. Baseline data collection occurred at 22 centres between March, 2006, and July, 2010, with a repeat assessment at one centre (Stockport) between August, 2012, and June, 2013, for a subset of these participants. Height and weight were objectively measured at both timepoints. We included individuals present at both timepoints with complete data in the analytic sample. Participants were aged 40–69 years and commuted from home to a workplace on a regular basis at both baseline and follow-up. Two exposures were investigated: transition from car commuting to active or public transport commuting and transition from active or public transport to car commuting. Change in BMI between baseline and repeat assessment was the outcome of interest, assessed with bivariate and multivariate logistic regression models. Findings 502 656 individuals provided baseline data, with 20 346 participating in the repeat assessment after a median of 4·4 years (IQR 3·7–4·9). 5861 individuals were present at both timepoints and had complete data for all analytic variables. Individuals who transitioned from car commuting at baseline to active or public transportation modes at follow-up had a decrease in BMI of −0·30 kg/m2 (95% CI −0·47 to −0·13; p=0·0005). Conversely, individuals who transitioned from active commuting at baseline to car commuting at follow-up had a BMI increase of 0·32 kg/m2 (0·13 to 0·50; p=0·008). These effects were not attenuated by adjustment for hypothesised confounders. Change in household income emerged as a determinant of commute mode transitions. Interpretation Incorporation of increased levels of physical activity as part of the commute to work could reduce obesity among middle-aged adults in the UK. Funding UK Medical Research Council.

Active commuting and obesity in mid-life: cross-sectional, observational evidence from UK Biobank

BACKGROUND Physical inactivity is a leading cause of obesity and premature mortality. We aimed to examine the relation between active commuting and obesity in mid-life using objectively measured anthropometric data from UK Biobank. METHODS Cross-sectional, observational data from UK Biobank were used. These were collected from individuals aged 40-69 years who visited 22 assessment centres across the UK between 2006 and 2010. Self-reported commuting method was operationalised into seven categories, ordered to reflect typical levels of physical exertion. The outcomes assessed were BMI (based on objectively measured weight and height) and percentage body fat. Hypothesised confounders were income, area deprivation, urban or rural residence, education, alcohol intake, smoking, leisure physical activity, recreational walking, occupational physical activity, general health, and limiting illness or disability. We used sex-stratified multivariate linear-regression models. FINDINGS Final complete case sample sizes were 72 999 men and 83 667 women for the BMI outcome and 72 139 men and 82 788 women for the percentage body fat outcome. Active commuting was significantly and independently associated with reduced BMI and percentage body fat for both sexes, with a graded pattern apparent across the seven commuting categories. In fully adjusted models, compared with their car-only counterparts, mixed public and active transport commuters had significantly lower BMI (men: β coefficient -1·00 kg/m(2) [95% CI -1·14 to -0·87], p<0·0001; women: -0·67 kg/m(2) [-0·86 to -0·47], p<0·0001), as did cycling or cycling and walking commuters (men: -1·71 kg/m(2) [95% CI -1·86 to -1·56], p<0·0001; women: -1·65 kg/m(2) [-1·92 to -1·38], p<0·0001). Similarly, compared with car-only commuters, mixed public transport and active commuters had significantly lower percentage body fat (men: -1·32% [95% CI -1·53 to -1·12], p<0·0001; women: -1·10% [-1·40 to -0·81], p<0·0001), as did cycling or cycling and walking commuters (men: -2·75% [95% CI -3·03 to -2·48], p<0·0001; women: -3·26% [-3·80 to -2·71], p<0·0001). INTERPRETATION This study is the first to use UK Biobank data to address the topic of active commuting and obesity and shows robust, independent associations between active commuting and healthier bodyweight and composition. These findings support the case for interventions to promote active travel as a population-level policy response for prevention of obesity in mid-life. FUNDING UK Medical Research Council.

Do local unemployment rates modify the effect of individual labour market status on psychological distress

This study investigates whether the unemployment rate of the area in which an individual lives affects their level of psychological distress, and the extent to which this is dependent on their own labour market status. Data were taken from the British Household Panel Survey (1991-2008) and longitudinal multiple membership multilevel modelling was carried out in order to account for the complex hierarchical structure of the data. The results suggest that living in an area with a high unemployment rate, defined by the claimant count, confers a degree of protection against the negative psychological effects of unemployment. However, psychological distress levels among unemployed people were still significantly and substantially higher than among their securely employed counterparts.

Investigating the effect of the London living wage on the psychological wellbeing of low-wage service sector employees: a feasibility study

BACKGROUND Working poverty has become a major public health concern in recent times, and low-paid, insecure employment has been widely linked to poor psychological wellbeing. The London Living Wage (LLW) campaign aims to ensure employees receive adequate pay. The objective of this study is to investigate whether working for a LLW employer predicted higher levels of psychological wellbeing among low-wage service sector employees. METHODS Workplace interviews were conducted with 300 service sector employees in London; 173 of whom were in LLW workplaces. Positive psychological wellbeing was measured using the Warwick-Edinburgh Mental Wellbeing Scale. Multivariate linear regression was used to assess whether working for a LLW employer was associated with greater psychological wellbeing, adjusting for hypothesised confounding and mediating factors. RESULTS After adjustment, respondents working for LLW employers had wellbeing scores 3.9 units higher on average than those who did not (95% CI: 1.8, 6.0). These empirical results are complemented by methodological findings regarding the difficulties associated with accessing the study group. CONCLUSIONS Those who worked for a LLW employer had significantly higher psychological wellbeing on average than those who did not. This was shown to be irrespective of any differences in the socioeconomic or demographic composition of these two groups.

Does active commuting protect against obesity in mid-life? Cross-sectional, observational evidence from UK Biobank.

Abstract Background The health benefits of physical activity are well understood. However, recent decades have seen declines in typical physical activity levels across populations in high and middle income countries. Active commuting has been promoted as a way to counteract the negative population health consequences of sedentary lifestyles. This study assessed the association between active commuting and obesity in mid-life with the use of objectively measured anthropometric data. Methods Baseline cross-sectional data (2006–10) from UK Biobank were used (502 664 participants aged 40–69 years, of whom 264 341 commuted). Self-reported commuting mode was operationalised across seven mode categories, ordered to indicate typical physical activity. Outcomes were objectively measured body-mass index (BMI) and percentage body fat (BF%). Hypothesised confounders were identified: commute frequency, income, area deprivation, urban or rural commute, education, alcohol use, smoking, leisure physical activity, occupational physical activity, general health, and limiting illness or disability. Interaction effects were found for sex, so sex-stratified, nested, multivariate linear regression models were estimated. Final complete case sample sizes were 71 353 men, 82 365 women (for BMI analysis); and 70 627 men, 81 504 women (BF%). Findings Active commuting was significantly and independently predictive of lower BMI and BF% for both men and women, with a dose-response pattern apparent across the seven mode categories. In the fully adjusted models, mixed active and public transport commuters had significantly lower BMI than did car-driving commuters (men −1·0 kg/m 2 , 95% CI −1·13 to −0·84; women −0·7, −0·85 to −0·48). Cycling predicted lower BMI (men −1·72 kg/m 2 , 95% CI −1·87 to −1·57; women −1·66, −1·91 to −1·42). A similar pattern and magnitude of effect was observed for BF%. Mixed active and public transport commuters had significantly lower BF% than did car users (men −1·3%, 95% CI −1·50 to −1·10; women −1·09, −1·38 to −0·80). Walking predicted lower BF% (men −1·2%, 95% CI −1·54 to −0·91; women −1·2, −1·34 to −0·98), and cyclists had significantly lower BF% (men −2·3%, 95% CI −3·03 to −2·47; women −3·3, −3·81 to −2·73). Sensitivity analyses to investigate the effects of item missingness, interactions, distance and frequency, and effects of energy intake did not affect the results. Interpretation This study is the first to our knowledge to use UK Biobank data to address the topic of active commuting and obesity; we found robust, independent associations between active commuting and healthier body weight and composition. This research supports the promotion of active commuting as a population-level policy response. Further research should make use of longitudinal data to provide stronger causal inference. Funding Medical Research Council Strategic Skills Postdoctoral Fellowship in Population Health (awarded to EF)

Retirement and physical activity

A recent analysis of the EPIC-Norfolk cohort by Barnett et al found that retirement was associated with a decline in overall levels of physical activity as decreases in occupational and transport-related activity were not compensated for by increases in household and recreational activity.1 This study adds more accurate assessment of physical activity with a larger sample size than previous studies2 and allows the breakdown of physical activity across different domains, as well as investigation of socioeconomic differences. Although the main finding has been echoed in some previous studies,3 ,4 a 2012 systematic review by the same authors concluded that the impacts of retirement on overall physical activity were unclear.5 This lack of clarity was due to the paucity of accurate activity assessment in included studies, a gap that this study addresses and strengthens our confidence that retirement is indeed a time of declining physical activity. The study raises the possibility that intervening around the time of retirement may be one strategy to deal with low levels of physical activity, which is noted a serious concern worldwide.6 Barnett et al also found greater declines in physical activity for those previously in manual jobs compared with those in non-manual jobs.1 This is a worrying yet familiar trend, …

Patterns and correlates of active commuting in adults with type 2 diabetes: cross-sectional evidence from UK Biobank

Objectives To describe the active commuting (AC) patterns of adults with type 2 diabetes and how these relate to physical activity and sedentary behaviour in UK Biobank. Social and environmental correlates of AC will also be explored. Design Cross-sectional analysis of a cohort study. Settings This is a population cohort of over 500 000 people recruited from 22 centres across the UK. Participants aged between 37 and 73 years were recruited between 2006 and 2010. Participants 6896 participants with a self-reported type 2 diabetes diagnosis who reported commuting to work and had complete covariate data were included in the analysis. Exposure measures Exposure measures were AC to work, measured as usual mode of transport. Outcome measures Outcome measures were weekly minutes of moderate to vigorous physical activity (MVPA), hours/day of sedentary time and participation in active travel. Results AC (reporting walking or cycling to work only) was reported by 5.5% of participants, with the great majority using the car to commute (80%). AC was associated with an additional 73 (95% CI 10.8 to 134.9) and 105 (95% CI 41.7 to 167.2) weekly minutes of MVPA for men and women, respectively. AC was associated with reduced sedentary time (β −1.1, 95% CI −1.6 to –0.7 hours/day for men; and β −0.8, 95% CI −1.2 to –0.3 hours/day for women). Deprivation and distance from home to work were identified as correlates of AC behaviour. Conclusions Rates of AC are very low in adults with type 2 diabetes. However, AC offers a potentially sustainable solution to increasing physical activity and reducing sedentary behaviour. Therefore, strategies to improve the environment and encourage AC may help to increase population levels of physical activity and reduce the disease burden associated with type 2 diabetes.

P131 Does switching to active commuting reduce BMI in mid-life? Longitudinal, observational evidence from UK Biobank

Background Physical inactivity is a leading cause of obesity, chronic disease and premature mortality. Middle-age is a key lifestage for the development of these risks. In this study, uptake of active commuting is hypothesised to independently predict decreases in bodyweight and bodyfat. Methods UK Biobank is a survey of individuals aged 40–69 at baseline (2006–2010; n = 502,656) selected via NHS patient registers. A subsample participated in a repeat assessment (2012–2013, n = 20,346). For this study, individuals with complete data on analytic variables at baseline and follow-up were selected (n = 4,132). BMI was calculated from objectively measured height and weight (kg/m2). Baseline BMI was subtracted from follow-up BMI to generate the outcome of interest: BMI change. Two binary exposure variables were derived from self-reported commuting mode: (i) experiencing a transition from car commuting at baseline to active/public modes at follow-up; (ii) transition from active/public modes at baseline to car commuting at follow-up (reference categories were those who had retained their baseline mode at follow-up). A range of time-varying and time-invariant socioeconomic, demographic, health and behavioural factors were identified as potential confounders. Nested multivariate linear regression models were fitted using Stata 14. All analyses were replicated using objectively measured percentage body fat change as a supplementary outcome. Results Experiencing a transition from car commuting at baseline to a public/active modes at follow-up (n = 469) independently predicted a −0.30 kg/m2 decrease in BMI (95% CI −0.48 to −0.13), compared with stable car commuting (n = 3,545). Conversely, experiencing a transition from active/public transport commuting to car commuting (n = 405) was significantly and independently predictive of a 0.32 kg/m2 increase in BMI (95% CI 0.13 to 0.50), when compared with stable use of active or public modes (n = 1,272). Adjustment for hypothesised time-varying and time-invariant socioeconomic, demographic, health and behavioural hypothesised confounders did not attenuate the effects of commute mode transition on BMI change. results from complementary percentage body fat analyses were corroborative. Conclusion To the authors’ knowledge, this study is the first to use UK Biobank’s nested cohort to investigate the effects of active commuting on adiposity. The findings suggest a causal relationship between active commuting and objectively measured markers for obesity in this middle-aged UK sample. Sample size constraints necessitated the combining of active and public modes, leading to probable underestimation of effects for walking and cycling. This research supports the case for interventions to promote active commuting as a population-level policy response to the prevention of obesity in mid-life.