Socioeconomic inequalities in childhood and adolescent body-mass index, weight, and height from 1953 to 2015: an analysis of four longitudinal, observational, British birth cohort studies

Background Socioeconomic inequalities in childhood body mass index (BMI) have been repeatedly documented in high income countries, yet there is uncertainty regarding how they have changed across time, how inequalities in the composite parts of BMI have changed (weight and height), and whether inequalities differ in magnitude across the outcome distributions. We investigated socioeconomic inequalities in childhood/adolescent weight, height, and BMI from 1953 to 2015 using British birth cohorts born in 1946, 1958, 1970, and 2001. Methods Associations between childhood social class and anthropometric outcomes at age 7, 10/11 and 14/16 years were examined to assess socioeconomic inequalities in each cohort using gender-adjusted linear regression models. Multilevel models were used to examine if these inequalities widened or narrowed from childhood to adolescence; quantile regression was used to examine whether the magnitude of inequalities differed across the outcome distribution. Findings Lower social class was associated with lower childhood/adolescent weight in earlier-born cohorts (1946-1970), yet with higher weight in the 2001 cohort. Lower social class was associated with shorter height in all cohorts, yet the absolute magnitude of this difference narrowed across generations. There was little inequality in childhood BMI in the 1946–1970 cohorts, yet inequalities were present in the 2001 cohort, and in all cohorts at 14/16 years (p<0.05 age x social class interactions). BMI and weight inequalities were larger in the 2001 cohort and systematically larger at higher quantiles—eg, in the 2001 cohort at 11 years there was a 0.98kg/m2 difference (0.63, 1.33) in median BMI (lowest to highest social class), yet 2.54kg/m2 (1.85, 3.22) difference at the 90th BMI percentile. Interpretation In the later 20th and early 21st centuries, socioeconomic inequalities in weight reversed, those in height narrowed, while inequalities in BMI and obesity emerged and widened. These drastic changes highlight the powerful impact of societal changes on child-adolescent growth and the insufficiency of previous policies in preventing obesity and its socioeconomic inequality. New and effective policies are required to reduce BMI inequalities in current and future children and adolescents. Without effective interventions, it is anticipated these inequalities will widen further throughout adulthood

Prevalence of reported difficulty with 16 physical capability tasks at age 60–64 among men in the MRC NSHD (N = 1001).

<p>For further details of tasks assessed see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155815#pone.0155815.t001" target="_blank">Table 1</a>.</p

Is the Hierarchy of Loss in Functional Ability Evident in Midlife? Findings from a British Birth Cohort

<div><p>Background</p><p>Difficulties performing a range of physical tasks of daily living have been shown to develop in older populations in a typically observed sequence, known as the hierarchy of loss. Nearly all previous research has been undertaken using populations aged over 75. This study aimed to use cross-sectional and longitudinal data to test for evidence of the hierarchy of loss from midlife onwards.</p><p>Methods</p><p>The prevalence of reported difficulty undertaking 16 physical tasks in the MRC National Survey of Health and Development at age 60–64 were calculated, with Mokken scaling used to confirm the hierarchical order. Logistic regression was used to calculate the odds ratios of reporting difficulty performing tasks at the bottom of the hierarchy (i.e. feeding, washing and/or toileting) at age 60–64 by reported difficulty at the top of the hierarchy (i.e. gripping, walking and/or stair climbing) at age 43.</p><p>Results</p><p>At age 60–64, tasks associated with balance, strength and co-ordination, such as climbing stairs, were the first tasks participants reported difficulty with and tasks associated with upper limb mobility, such as feeding yourself, were the last. In a fully-adjusted model, participants who reported difficulty at the top of the hierarchy at age 43 were 2.85 (95% CI: 1.45–5.60) times more likely to report difficulty with tasks at the bottom of the hierarchy at age 60–64.</p><p>Conclusion</p><p>This study presents evidence of the hierarchy of loss in a younger population than previously observed suggesting that targeted interventions to prevent functional decline should not be delayed until old age.</p></div

Characteristics of participants from the MRC National Survey of Health and Development (based on sample included in logistic regression analyses, maximum N = 2106).

<p>Characteristics of participants from the MRC National Survey of Health and Development (based on sample included in logistic regression analyses, maximum N = 2106).</p

Odds ratios of progressing through the hierarchy of loss between ages 43 and 60–64 years in the MRC NSHD.

<p>Odds ratios of progressing through the hierarchy of loss between ages 43 and 60–64 years in the MRC NSHD.</p

Is the Hierarchy of Loss in Functional Ability Evident in Midlife? Findings from a British Birth Cohort - Fig 3

<p>Prevalence of reported difficulty gripping, walking 400m and climbing stairs at ages 43, 53 and 60–64 ((A) Men (N = 957) (B) Women (N = 1089)).</p

Self-reported difficulty with physical capability tasks assessed in the MRC NSHD at ages 43, 53 and 60–64 years.

<p>Self-reported difficulty with physical capability tasks assessed in the MRC NSHD at ages 43, 53 and 60–64 years.</p

Study-stratified box plots for height, weight, and BMI Z-scores according to the UK-WHO chart at 10 or 11 years of age.

<p>BMI: Body Mass Index, UK-WHO: United Kingdom-World Health Organisation, NSHD: Medical Research Council National Survey of Health and Development, NCDS National Child Development Study, BCS: British Cohort Study, ALSPAC: Avon Longitudinal Study of Parents and Children, MCS: Millennium Cohort Study.</p

Trajectories of the probability of overweight or obesity (versus normal weight) from sex- and study-stratified multilevel logistic regression models.

<p>NSHD: Medical Research Council National Survey of Health and Development, NCDS National Child Development Study, BCS: British Cohort Study, ALSPAC: Avon Longitudinal Study of Parents and Children, MCS: Millennium Cohort Study.</p

The 98th, 91st, and 50th childhood BMI centiles from sex- and study-stratified LMS models plotted against the IOTF cut-offs.

<p>BMI: Body Mass Index, IOTF: International Obesity Task Force, LMS: Lambda-Mu-Sigma, NSHD: Medical Research Council National Survey of Health and Development, NCDS National Child Development Study, BCS: British Cohort Study, ALSPAC: Avon Longitudinal Study of Parents and Children, MCS: Millennium Cohort Study.</p