Summer to winter variability in the step counts of normal weight and overweight adults living in the UK

BACKGROUND: This study investigated whether pedometer-determined activity varies between summer and winter in normal-weight and overweight adults. METHODS: Forty-five normal-weight (58% female, age = 39.1 ± 12.4 years, BMI = 22.2 ± 2.1 kg/m2) and 51 overweight (49% female, age = 42.1 ± 12.5 years, BMI = 29.3 ± 4.5 kg/m2) participants completed a within-subject biseasonal pedometer study. All participants completed 2 4-week monitoring periods; 1 period in the summer and 1 period the following winter. Changes in step counts across seasons were calculated and compared for the 2 BMI groups. RESULTS: Both BMI groups reported significant summer to winter reductions in step counts, with the magnitude of change being significantly greater in the normal-weight group (–1737 ± 2201 versus –781 ± 1673 steps/day, P = .02). Winter step counts did not differ significantly between the 2 groups (9250 ± 2845 versus 8974 ± 2709 steps/day, P = .63), whereas the normal-weight group reported a significantly higher mean daily step count in the summer (10986 ± 2858 versus 9755 ± 2874 steps/day, P = .04). CONCLUSION: Both normal-weight and overweight individuals experienced a reduction in step counts between summer and winter; however, normal-weight individuals appear more susceptible to winter decreases in ambulatory activity, with the greatest seasonal change occurring on Sundays. Effective physical activity policies should be seasonally tailored to provide opportunities to encourage individuals to be more active during the winter, particularly on weekends

UK adults exhibit higher step counts in summer compared to winter months

Background: Seasonal differences in step counts have been observed in a limited number of studies conducted on US adults. Due to the diverse global climate, assessment and interpretation of seasonal patterns in ambulatory activity may vary between countries, and regionally specific studies are necessary to understand global patterns. Currently, no studies have assessed whether a seasonal trend is present when ambulatory activity is measured objectively in adults living in the UK. Aim: To investigate whether pedometer-determined step counts of adults living in the UK vary between summer and winter. Subjects and methods: Ninety-six adults (52% male, age = 41.0 ± 12.3 years, BMI = 26.1 ± 5.1 kg/m2) completed a within-subject bi-seasonal pedometer study. All participants completed two four-week monitoring periods; one during the summer and one the following winter. The same Yamax SW-200 pedometer was worn throughout waking hours during both seasons, and daily step counts were recorded in an activity log. Intra-individual seasonal changes in mean daily steps were analysed using a paired samples t-test. Results: Summer mean daily step counts (10417 ± 3055 steps/day) were significantly higher than those reported during the winter (9132 ± 2841 steps/day) (p < 0.001). A follow-up study conducted the subsequent summer in a sub-sample (n = 28) reinforced this trend. Summer step counts were significantly higher than winter step counts on all days of the week (p ≤ 0.001). A significant day of the week effect was present in both seasons, with step counts reported on a Sunday being on average 1,500 steps/day lower than those reported Monday through to Saturday. Conclusion: Step counts in the sample of UK adults surveyed decreased significantly in the winter compared to the summer, suggesting future pedometer surveillance studies should capture step counts throughout the year for a non-biased reflection of habitual ambulatory activity. Public health initiatives should target these seasonal differences and opportunities should be provided which encourage individuals to increase their activity levels during the colder, darker months of the year

How can we learn about community socioeconomic status and poverty in a developing country urban environment? An example from Johannesburg-Soweto, South Africa

Few tested tools exist to assess poverty and socio-economic status at the community level, particularly in urban developing country environments. Furthermore, there is no real sense of what the community concept actually means. Consequently, this paper aims to describe how formative qualitative research was used to develop a quantitative tool to assess community SES in Johannesburg-Soweto in terms of the terminology used, topics covered, and how it was administered, comparing it to the South African Living Standards and Measurement Study. It also discusses the level of aggregation respondents identified as defining a local community using a drawing/mapping exercise. Focus groups (n=11) were conducted with 15-year-old adolescents and their caregivers from the 1990 Birth-to-Twenty (Bt20) cohort and key informant in-depth interviews (n=17) with prominent members working in the Bt20 communities. This research recognises the importance of involving local people in the design of data collection tools measuring poverty and human well-being

Socio-economic influences on anthropometric status in urban South African adolescents: sex differences in the Birth to Twenty Plus cohort.

OBJECTIVE: To investigate the associations of household and neighbourhood socio-economic position (SEP) with indicators of both under- and overnutrition in adolescents and to explore sex differences. DESIGN: Analysis of anthropometric, household and neighbourhood SEP data from the Birth to Twenty Plus cohort born in 1990. Anthropometric outcomes were BMI (thinness, overweight and obesity) and percentage body fat (%BF; low, high). Associations between these and the household wealth index, caregiver education and neighbourhood SEP tertile measures were examined using binary logistic regression. SETTING: Johannesburg-Soweto, South Africa. SUBJECTS: Adolescents aged 17-19 years (n 2019; 48·2% men). RESULTS: Women had a significantly higher combined prevalence of overweight/obesity (26·2%) than men (8·2%) whereas men had a significantly higher prevalence of thinness than women (22·2% v. 10·6%, respectively). Having a low neighbourhood social support index was associated with higher odds of high %BF in women (OR=1·59; 95% CI 1·03, 2·44). A low household wealth index was associated with lower odds of both overweight (OR=0·31; 95% CI 0·12, 0·76) and high %BF in men (OR=0·28; 95% CI 0·10, 0·78). A low or middle household wealth index was associated with higher odds of being thin in men (OR=1·90; 95% CI 1·09, 3·31 and OR=1·80; 95% CI 1·03, 3·15, respectively). For women, a low household wealth index was associated with lower odds of being thin (OR=0·49; 95% CI 0·25, 0·96). CONCLUSIONS: The study highlights that even within a relatively small urban area the nutrition transition manifests itself differently in men and women and across SEP indicators. Understanding the challenges for different sexes at different ages is vital in helping to plan public health services

Association of socioeconomic status change between infancy and adolescence, and blood pressure, in South African young adults: Birth to Twenty Cohort

ObjectiveSocial epidemiology models suggest that socioeconomic status (SES) mobility across the life course affects blood pressure. The aim of this study was to investigate the association between SES change between infancy and adolescence, and blood pressure, in young adults, and the impact of early growth on this relationship.SettingData for this study were obtained from a ‘Birth to Twenty’ cohort in Soweto, Johannesburg, in South Africa.ParticipantsThe study included 838 Black participants aged 18 years who had household SES measures in infancy and at adolescence, anthropometry at 0, 2, 4 and 18 years of age and blood pressure at the age of 18 years.MethodsWe computed SES change using asset-based household SES in infancy and during adolescence as an exposure variable, and blood pressure and hypertension status as outcomes. Multivariate linear and logistic regressions were used to investigate the associations between SES change from infancy to adolescence, and age, height and sex-specific blood pressure and hypertension prevalence after adjusting for confounders.ResultsCompared to a persistent low SES, an upward SES change from low to high SES tertile between infancy and adolescence was significantly associated with lower systolic blood pressure (SBP) at the age of 18 years (β=−4.85; 95% CI −8.22 to −1.48; p<0.01; r2=0.1804) after adjusting for SES in infancy, small-for-gestational-age (SGA) and weight gain. Associations between SES change and SBP were partly explained by weight gain between birth and the age of 18 years. There was no association between SES mobility and diastolic blood pressure, mean arterial pressure or hypertension status.ConclusionsOur study confirms that upward SES change has a protective effect on SBP by the time participants reach young adulthood. Socioeconomic policies and interventions that address inequality may have the potential to reduce cardiovascular disease burden related to BP in later life

How well do waist circumference and body mass index reflect body composition in pre-pubertal children?

Objective: To investigate the quantitative relationship between WC and height and subsequently the association between Waist Circumference Index (WCI), BMI, and body composition in pre-pubertal children. Design: Cross-sectional sample (n = 227; boys = 127) of pre-pubertal Black children (age range 8.8 to 11.0 years) from the Bone Health sub-study of the Bt20 birth cohort study set in Soweto-Johannesburg, South Africa. Measures of height, weight, and waist circumference by anthropometry, total and truncal fat and lean mass by Dual-energy X-ray Absorptiometry (DXA) were used in the analysis. Pearson’s correlation coefficients were used to examine the associations between BMI, WC, and body composition outcomes. Results: WC was independent of height when height was raised to a power of approximately 0.8. BMI and WCI (WC/Ht) were significantly associated with total and truncal fat and lean mass in both sexes (all P < 0.001). BMI demonstrated consistently and significantly higher correlations with body composition than WCI and this association was significantly greater for fat mass than lean mass. Conclusion: BMI, rather than WCI, would be a better screening tool for total and truncal fat mass in both sexes prior to puberty

Is puberty starting earlier in urban South Africa?

Age at the initation of pubertal development was estimated for 401 Black (212 boys) and 206 White (100 boys) urban South African adolescents born in Soweto-Johannesburg in 1990. Average age at the initation of puberty, assessed by age at the transition from Tanner stage 1 to Tanner stage 2 for breast/genitalia or pubic hair development ranged between 9.8 and 10.5 years. There were no statistically significant differences in age at initiation between genders or ethnic groups. Age at the initation of pubertal development has remained stable over the last 10 to 15 years, with the exception of pubic hair in boys which has declined on average 1.3 years over a decade. There is evidence to suggest that the tempo of pubertal maturation is increasing in girls born in the Soweto-Johannesburg area, however, the evidence is less clear for boys

Age at menarche and the evidence for a positive secular trend in urban South Africa

Menarcheal age was estimated for 287 (188 Black; 99 White) urban South African girls born in Soweto-Johannesburg in 1990. The median menarcheal age for Blacks was 12.4 years (95% confidence interval [CI] 12.2, 12.6) and 12.5 years (95% CI 11.7, 13.3) for Whites. Data from six studies of menarcheal age, including the current study, were analyzed to examine the evidence for a secular trend between 1956 and 2004 in urban South African girls. There was evidence of a statistically significant secular trend for Blacks, but not Whites. Average menarcheal age for Blacks decreased from 14.9 years (95% CI 14.8, 15.0) in 1956 to 12.4 years (95% CI 12.2, 12.6) in the current study, an average decline of 0.50 years per decade. Fewer data were available for Whites, but average menarcheal age decreased from 13.1 years (95% CI 13.0, 13.2) in 1977 to 12.5 years (95% CI 11.7, 13.3) in the current study, an average decline of 0.22 years per decade. The diminishing age at menarche and the current lack of difference between Blacks and Whites is probably reflective of the continuing nutritional and socio-economic transition occurring within South Africa

Associations between household and neighbourhood socioeconomic status and systolic blood pressure among urban South African adolescents.

Factors resulting in high risk for cardiovascular disease have been well studied in high income countries, but have been less well researched in low/middle income countries. This is despite robust theoretical evidence of environmental transitions in such countries which could result in biological adaptations that lead to increased hypertension and cardiovascular disease risk. Data from the South African Birth to Twenty cohort, Bone Health sub-sample (n = 358, 47% female), were used to model associations between household socioeconomic status (SES) in infancy, household/neighbourhood SES at age 16 years, and systolic blood pressure (multivariate linear regression) and risk for systolic pre-hypertension (binary logistic regression). Bivariate analyses revealed household/neighbourhood SES measures that were significantly associated with increased systolic blood pressure. These significant associations included improved household sanitation in infancy/16 years, caregiver owning the house in infancy and being in a higher tertile (higher SES) of indices measuring school problems/environment or neighbourhood services/problems/crime at 16 years of age. Multivariate analyses adjusted for sex, maternal age, birth weight, parity, smoking, term birth, height/body mass index at 16 years. In adjusted analyses, only one SES variable remained significant for females: those in the middle tertile of the crime prevention index had higher systolic blood pressure (β = 3.52, SE = 1.61) compared with the highest tertile (i.e. those with the highest crime prevention). In adjusted analyses, no SES variables were significantly associated with the systolic blood pressure of boys, or with the risk of systolic pre-hypertension in either sex. The lack of association between SES and systolic blood pressure/systolic pre-hypertension at age 16 years is consistent with other studies showing an equalization of adolescent health inequalities. Further testing of the association between SES and systolic blood pressure would be recommended in adulthood to see whether the lack of association persists

Age at menarche and the evidence for a positive secular trend in urban South Africa

Menarcheal age was estimated for 287 (188 Black; 99 White) urban South African girls born in Soweto-Johannesburg in 1990. The median menarcheal age for Blacks was 12.4 years (95% confidence interval [CI] 12.2, 12.6) and 12.5 years (95% CI 11.7, 13.3) for Whites. Data from six studies of menarcheal age, including the current study, were analyzed to examine the evidence for a secular trend between 1956 and 2004 in urban South African girls. There was evidence of a statistically significant secular trend for Blacks, but not Whites. Average menarcheal age for Blacks decreased from 14.9 years (95% CI 14.8, 15.0) in 1956 to 12.4 years (95% CI 12.2, 12.6) in the current study, an average decline of 0.50 years per decade. Fewer data were available for Whites, but average menarcheal age decreased from 13.1 years (95% CI 13.0, 13.2) in 1977 to 12.5 years (95% CI 11.7, 13.3) in the current study, an average decline of 0.22 years per decade. The diminishing age at menarche and the current lack of difference between Blacks and Whites is probably reflective of the continuing nutritional and socio-economic transition occurring within South Africa