Sugar-sweetened beverage intake and relative weight gain among South African adults living in resource-poor communities: longitudinal data from the STOP-SA study.

OBJECTIVES: This study examines the prospective association between sugar-sweetened beverages (SSB) consumption and change in body weight over a 4-5-year period in a socio-economically disadvantaged South African population. METHODS: This is a longitudinal study involving 800 adults (212 men, 588 women); 247 from the original METS (Modelling the Epidemiological Transition Study) cohort (N = 504) and 553 of the original 949 members of the PURE (Prospective Urban and Rural Epidemiology) Study. Both cohorts were drawn from low-income, socio-economically disadvantaged communities. Mean follow-up duration and age were 4.5 (SD 0.45) and 50.0 (SD 11.8) years, respectively. Harmonised measurements included body mass index, self-reported moderate-to-vigorous physical activity, and intake of meat, snacks and 'take-aways', fruits and vegetables and SSB (in servings/week). Multivariate logistic regression models were developed to determine the extent to which SSB consumption predicted relative weight gain, after controlling for potential confounders and known predictors. RESULTS: Nearly a third (29%) of participants had a relative weight change ≥5.0%; higher in the non-obese compared to the obese group (32% vs. 25%; p = 0.026). The average SSB consumption was 9.9 servings/week and was higher in the food insecure compared to the food secure group (11.5 vs. 9.0 servings/week; p = 0.006); but there were no differences between women and men (10.3 vs. 9.1 servings/week; p = 0.054). Mean SSB consumption was higher in the group who gained ≥5% weight compared to those who did not (11.0 vs. 8.7; p = 0.004). After adjustment, SSB consumption of 10 or more servings/week was associated with a 50% greater odds of gaining at least 5% body weight (AOR: 1.50, 95% CI (1.05-2.18)). CONCLUSION: These results show that higher intake of SSB predicts weight gain in a sample of South Africans drawn from low-income settings. Comprehensive, population-wide interventions are needed to reduce SSB consumption in these settings.

Metacarpal Indices and Their Association with Fracture in South African Children and Adolescents.

This prospective study assessed whether metacarpal indices predict fracture risk in children and adolescents. Radiogrammetry was performed at the second metacarpal midshaft on annual hand-wrist radiographs of 359 South African (SA) children aged 10-17 years. Bone length, bone width, and medullary width were measured, and the following proxies for bone strength calculated: metacarpal index (MCI), bone mineral density (BMD), section modulus (SM), stress-strain index (SSI), and slenderness index (SLI). Height and weight were measured annually. Self-reported physical activity (PA) and fracture history were obtained at ages 15 years (for the preceding 12 months) and 17 years, respectively. At 17 years, 82 (23%) participants (black, 16%; white, 42%; p < 0.001) reported a previous fracture. None of the bone measures or indices were associated with fracture in black participants. In white females, after adjusting for PA, a 1 standard deviation (SD) greater SLI doubled the fracture risk [odds ratio (OR) 2.08; 95% confidence interval (CI) 1.08, 3.98]. In white males, a 1 SD greater BMD was associated with a 2.62-fold increase in fracture risk (OR 3.62; 95% CI 1.22, 10.75), whilst a 1 SD greater SM (OR 2.29; 95% CI 1.07, 4.89) and SSI (OR 2.23; 95% CI 1.11, 4.47) were associated with a more than twofold increase in fracture risk, after height, and PA adjustment. No single index consistently predicted fracture across the four groups possibly due to ethnic and sex differences in bone geometry, muscle mass, and skeletal loading. Metacarpal radiogrammetry did not reliably predict fracture in SA children.

A longitudinal comparison of appendicular bone growth and markers of strength through adolescence in a South African cohort using radiogrammetry and pQCT.

To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally. Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. Weight- and non-weight-bearing bones have different growth and strength patterns. INTRODUCTION: Functional loading modulates bone size and strength. METHODS: To compare growth patterns and strength of weight- and non-weight-bearing bones longitudinally, we performed manual radiogrammetry of the second metacarpal on hand-wrist radiographs and measured peripheral quantitative computed tomography images of the radius (65%) and tibia (38% and 65%), annually on 372 black and 152 white South African participants (ages 12-20 years). We aligned participants by age from peak metacarpal length velocity. We assessed bone width (BW, mm); cortical thickness (CT, mm); medullary width (MW, mm); stress-strain index (SSI, mm3); and muscle cross-sectional area (MCSA, mm2). RESULTS: From 12 to 20 years, the associations between metacarpal measures (BW, CT and SSI) and MCSA at the radius (males R2 = 0.33-0.45; females R2 = 0.12-0.20) were stronger than the tibia (males R2 = 0.01-0.11; females R2 = 0.007-0.04). In all groups, radial BW, CT and MW accrual rates were similar to those of the metacarpal, except in white females who had lower radial CT (0.04 mm/year) and greater radial MW (0.06 mm/year) accrual. In all groups, except for CT in white males, tibial BW and CT accrual rates were greater than at the metacarpal. Tibial MW (0.29-0.35 mm/year) increased significantly relative to metacarpal MW (- 0.07 to 0.06 mm/year) in males only. In all groups, except white females, SSI increased in each bone. CONCLUSION: Irrespective of sex and ethnicity, metacarpal growth was similar to that of the non-weight-bearing radius but differed from that of the weight-bearing tibia. The local and systemic factors influencing site-specific differences require further investigation. Graphical abstract.

Results from the healthy active kids South Africa 2018 report card

Background. Healthy Active Kids South Africa (HAKSA) Report Cards were produced in 2007, 2010, 2014 and 2016. Objective. The 2018 Report Card aims to report on the latest available evidence relating to the physical activity (PA), nutrition and body composition of South African (SA) children and adolescents. Methods. A review was conducted using the following databases: PubMed; Africa Journals Online; and Africa-Wide (EBSCOhost). Articles published from January 2016 to September 2018 were included for review by the HAKSA scientific advisory group. Data were extracted, and a grade for each indicator was assigned based on the available evidence and the consensus of the scientific advisory group. This included 12 PA indicators, 6 nutrition indicators and 3 body composition indicators. Results. There was no evidence of a significant change in any of the indicators since the 2016 Report Card. Grades for certain indicators have been downgraded (from 2016) to bring these to the attention of relevant stakeholders and industry. These include food insecurity and grades that relate to the implementation of policy on PA and nutrition in the school environment, and on advertising and media relating to nutrition. Conclusion. Key priorities for action include: safe opportunities for physical activity; minimising the gap between policy and implementation (school culture and environment, and government strategies); and the double burden of over- and undernutrition, which relates to the continuing concern about food insecurity in SA. There is a need for further research, including surveillance, on all indicators, for future Report Cards

Maternal and early life nutrition and physical activity: setting the research and intervention agenda for addressing the double burden of malnutrition in South African children.

Early life is important for later health outcomes, yet there are few studies which adequately address all of the potential early life insults that may affect later life health and growth trajectories. This is particularly evident in low- to middle-income countries such as South Africa, where women of childbearing age are particularly vulnerable to high levels of physical inactivity, malnutrition, and obesity. Pregnancy may therefore be an opportune time to change behaviours and improve maternal and offspring health outcomes, and decrease the inter-generational transfer of risk. We show clear evidence that physical activity and nutrition are important target areas for intervention during pregnancy and in the early years of life, yet that current literature in Africa, and specifically South Africa, is limited. We have outlined the available literature concerning the impact of maternal and early life nutrition and physical activity on the health status of South African children, and have provided some recommendations for future research and policy.

Incidence and prevalence of type 2 diabetes mellitus with HIV infection in Africa: a systematic review and meta-analysis.

OBJECTIVES: This systematic review aims to investigate the incidence and prevalence of type 2 diabetes mellitus (T2DM) in patients with HIV infection in African populations. SETTING: Only studies reporting data from Africa were included. PARTICIPANTS: A systematic search was conducted using four databases for articles referring to HIV infection and antiretroviral therapy, and T2DM in Africa. Articles were excluded if they reported data on children, animals or type 1 diabetes exclusively. MAIN OUTCOME MEASURES: Incidence of T2DM and prevalence of T2DM. Risk ratios were generated for pooled data using random effects models. Bias was assessed using an adapted Cochrane Collaboration bias assessment tool. RESULTS: Of 1056 references that were screened, only 20 were selected for inclusion. Seven reported the incidence of T2DM in patients with HIV infection, eight reported the prevalence of T2DM in HIV-infected versus uninfected individuals and five reported prevalence of T2DM in HIV-treated versus untreated patients. Incidence rates ranged from 4 to 59 per 1000 person years. Meta-analysis showed no significant differences between T2DM prevalence in HIV-infected individuals versus uninfected individuals (risk ratio (RR) =1.61, 95% CI 0.62 to 4.21, p=0.33), or between HIV-treated patients versus untreated patients (RR=1.38, 95% CI 0.66 to 2.87, p=0.39), and heterogeneity was high in both meta-analyses (I2=87% and 52%, respectively). CONCLUSIONS: Meta-analysis showed no association between T2DM prevalence and HIV infection or antiretroviral therapy; however, these results are limited by the high heterogeneity of the included studies and moderate-to-high risk of bias, as well as, the small number of studies included. There is a need for well-designed prospective longitudinal studies with larger population sizes to better assess incidence and prevalence of T2DM in African patients with HIV. Furthermore, screening for T2DM using gold standard methods in this population is necessary. TRIAL REGISTRATION NUMBER: PROSPERO42016038689.

Cardiorespiratory fitness levels and associations with physical activity and body composition in young South African adults from Soweto.

BACKGROUND: This observational study aims to describe fitness, and objectively measured physical activity levels and patterns in 409 young black South African adults (aged 19-20 years) from Soweto, as well as to examine associations between physical activity, fitness and BMI. METHODS: A sub-maximal ramped step test was used to obtain an estimate of maximal oxygen uptake (VO2max). Physical activity was measured using ActiGraph (GT1M) for 7 days in 256 participants. Time spent in sedentary (<100 counts per minute (cpm)), moderate (2020-5998 cpm) and vigorous (≥5999 cpm) intensity activity was calculated, and 90% of participants were considered active. Data are presented as mean(CI) or median(CI). RESULTS: Overweight and obesity was more prevalent in females than males (35% vs 8%, p < 0.001). Males had a higher VO2max than females (41.9(41, 43) vs 32.6(32, 33)mlO2/kg/min, p < 0.001); spent more time in moderate to vigorous intensity physical activity (MVPA) (83(80, 94) vs 43(38, 45)min/day, p < 0.001), and less time in sedentary behaviours (541(541, 567) vs 575(568, 597)min/day, p < 0.01). Sedentary time was not associated with VO2max, however BMI was inversely associated, and MVPA was positively associated, with VO2max (both p < 0.001). CONCLUSIONS: The majority of young South African adults in this study were sufficiently active, and higher MVPA was associated with fitness. However, the high level of sedentary behaviour in this population is of concern and may be contributing to the increasing prevalence of overweight and obesity in this population. Young South African females are at greatest risk for decreased cardiovascular fitness and should be the focus for future interventions.

A scoping review examining physical activity measurement and levels in the first 2 years of life.

BACKGROUND: The first few years of life have been identified as a critical stage in the development of activity behaviours, which have been shown to track into later life. This scoping review aims to assess the literature reporting on physical activity levels in the first 2 years of life in order to answer two main questions: (i) how is physical activity measured in this age group? and (ii) how active are infants and toddlers in the first 2 years of life? METHODS: A search strategy was employed using PubMed with restrictions only on age and language. After applying exclusion criteria, 20 papers were included in the results. RESULTS: Seventeen studies used some form of objective assessment of physical activity (accelerometers, actometers, direct observation, doubly labelled water or a metabolic chamber); while the remaining three relied on subjective assessments (parent reported questionnaires or interviews, and activity diaries). Nine studies exclusively assessed infants (<12 months), and five exclusively assessed toddlers (>12 months). Only six studies reported physical activity levels and patterns specifically; most included studies measured activity as a covariate or correlate. Therefore, much of the reported data was difficult to assess, as results were vague or incompletely described. Where data were reported sufficiently for analysis, results were equally conflicted regarding whether toddlers were meeting recommended physical activity guidelines. CONCLUSIONS: This scoping review re-iterates the fact that more studies need to be conducted, which focus primarily on measuring and reporting physical activity levels and patterns in this age group in a comprehensive and standardized way, so that more informed guidelines can be devised and interventions can be designed and implemented where necessary.

A comparison of body composition estimates using dual-energy X-ray absorptiometry and air-displacement plethysmography in South African neonates.

BACKGROUND/OBJECTIVES: Neonatal body composition is an important predictor of future metabolic risk; however, the comparability of objective assessment techniques, particularly in African populations undergoing rapid health transition, is not known. This paper compares body composition estimates by air-displacement plethysmography (ADP) and dual-energy X-ray absorptiometry (DXA) in South African neonates. SUBJECTS/METHODS: Fat mass, fat-free mass and body fat percentage (%fat) estimates by ADP and DXA were compared in 88 urban, black South African neonates. The level of agreement between the techniques was assessed using Bland-Altman analyses. RESULTS: Significant correlations were observed between ADP and DXA measurements of fat mass (r=0.766), fat-free mass (r=0.942) and %fat (r=0.630); however, ADP estimates of fat mass (408±172 g vs 337±165 g; P<0.001) and %fat (12.9±4.4% vs 9.9±4%; P<0.001) were significantly higher and fat-free mass (2681±348 g vs 2969±375 g; P<0.001) significantly lower than those by DXA. Fat-free mass estimates showed greater consistency in the level of agreement between the techniques compared with fat and %fat estimates where the differences between methods were less predictable. CONCLUSION: Although ADP and DXA body composition estimates are highly correlated in neonates, significant differences are observed between the techniques. This is particularly relevant for fat mass and %fat estimates, where differences are highly variable between methods. Further investigation is needed to minimise inter-method differences to ensure accurate and comparable assessment of body composition at birth and across longitudinal study follow-up.

Impact of social norms and social support on diet, physical activity and sedentary behaviour of adolescents: a scoping review.

The prevalence of non-communicable diseases (NCDs) in adulthood is rapidly increasing, and it is essential that risk factors for NCDs be addressed in adolescence, both for the health of individuals during adolescence and for their health in later life. These risk factors include diet, physical activity and sedentary behaviour. No literature has been published that comprehensively summarizes the impact of social norms and social support on these behaviours among adolescents. Therefore, a scoping review was conducted to determine the extent of recent (since 2000) literature available on this topic. A comprehensive search strategy was used to search PubMed and EMBASE for eligible reviews. Review papers (narrative reviews, systematic and non-systematic reviews) published in English in peer-reviewed journals from 2000 to February 2013 were included in the overview. Two of the authors screened the titles and abstracts of the search results independently. Thirty reviews were included in the scoping review. This scoping review has shown sufficient evidence for parental influences, and especially the positive impact of an authoritative parenting style, on healthy behaviours of adolescents, although the evidence is somewhat more compelling for diet than for physical activity and sedentary behaviour. More research is needed to investigate parental and family influences on physical activity and sedentary behaviour. And the effect of peer influences on diet, physical activity and sedentary behaviour of adolescents requires further investigation. The evidence presented affirms the consideration of social norms and social support in the development of interventions to address these behaviours in adolescents. The evidence regarding parenting style provides some concrete guidance for such interventions.

Ethnic-specific cut-points for sarcopenia: evidence from black South African women.

BACKGROUND/OBJECTIVES: Age-related muscle and fat mass (FM) changes are ethnicity specific. We aimed to develop a cut-point for the muscle mass component of sarcopenia for black South African (SA) women, and to assess its predictive value, in comparison to established cut-points, to identify functional ability among older black SA women. SUBJECTS/METHODS: In a cross-sectional study, a sarcopenia cut-point was calculated from dual energy X-ray absorptiometry (DXA)-derived appendicular skeletal muscle mass (ASM) indexes (ASMI) from two young black SA reference groups. The new cut-point was compared with the most recent Foundation for the National Institutes of Health (FNIH) criteria (ASM <15.02 kg; and ASM(BMI) <0.512), an internationally accepted cut-point (ASMI <5.5 kg/m(2)) and a residual method adjusting for FM. All cut-points were then applied to 221 older black women to predict gait speed and handgrip strength. RESULTS: A cut-point of ASMI <4.94 kg/m(2) was derived from the young SA reference groups. Using this cut-point, 9.1% of older women were classified as sarcopenic, compared with 16.7-38.7% using other cut-points. The only cut-points that significantly predicted low functional ability (low gait speed and low handgrip strength) in older black women were the new SA cut-point and the FNIH ASM criterion. Multivariate logistic regression models for both these cut-points significantly predicted low handgrip strength (odds ratio (OR)=3.71, P=0.007 and OR=3.42, P=0.001, respectively) and low gait speed (OR=9.82, P=0.004 and OR=8.71, P=0.008, respectively). CONCLUSIONS: The new SA cut-point had similar or greater odds of predicting reduced functional ability in older SA women when compared with other internationally accepted cut-points.

Osteogenic effects of a physical activity intervention in South African black children.

OBJECTIVES: To determine whether a weight-bearing physical activity intervention improves measures of bone density, size and strength in a pre- and early pubertal cohort of black South African children. METHODS: Twenty two school children (9.7±1.1 years) were cluster randomised into an exercise (EX; n=12) and control (CON; n=10) group. EX children performed a weight-bearing exercise program for 20 weeks. CON children continued their regular activities. Whole body DXA and tibial peripheral QCT scans were obtained. Urine was analysed for concentrations of cross-linked N-telopeptides of Type I collagen (NTX). RESULTS: Changes in 4% volumetric BMD, area and strength were greater in EX than CON. At the 38% site, change in bone area and density was greater in EX than CON. The greater change in periosteal circumference in the EX groups also resulted in a greater change in cortical thickness of the tibia compared to the CON group. NTX concentration was lower in the EX group than the CON group after the intervention. CONCLUSIONS: This study documents for the first time the beneficial response of trabecular and cortical bone of black children to a weight bearing exercise intervention.

Ethnic differences in microvascular function in apparently healthy South African men and women.

Microvascular dysfunction precedes the clinical manifestations of cardiovascular disease. Given the ethnic disparities in cardiovascular disease, we aimed to investigate ethnic differences in microvascular endothelial function in a group of young (18-33 years old), apparently healthy individuals (n = 33, nine Black African, 12 mixed ancestry and 12 Caucasian). Microvascular endothelium-dependent and -independent function was assessed by laser Doppler imagery and iontophoresis of ACh and sodium nitroprusside (SNP), respectively, adjusting for skin resistance. Microvascular reactivity was expressed as maximum absolute perfusion, percentage change from baseline and area under the curve (AUC). Skin resistance was significantly lower in the Caucasian group in response to ACh (Caucasian, mean 0.16 ± 0.03 Ω versus Black, 0.21 ± 0.04 Ω and mixed ancestry, 0.20 ± 0.02 Ω, P < 0.01) and SNP (Caucasian, 0.08 ± 0.01 Ω versus Black, 0.11 ± 0.02 Ω and mixed ancestry, 0.12 ± 0.01 Ω, P < 0.01). Microvascular function in response to ACh was significantly higher in the Caucasian group compared with the other two groups; however, after adjusting for skin resistance these differences were no longer significant. Conversely, the microvascular SNP response remained significantly higher in the Caucasian group, even after adjusting for skin resistance (P < 0.01). Diastolic blood pressure was inversely associated with the AUC of ACh (r = -0.4) and all SNP responses (r = -0.3 to -0.6). Skin resistance was inversely associated with AUC and maximum absolute ACh response (r = -0.59 and -0.64, respectively) and all SNP responses (r = -0.37 to -0.79). Ethnic differences in endothelium-independent microvascular function may contribute to ethnic disparities in cardiovascular disease. Moreover, skin resistance plays a significant role in the interpretation of the microvascular response to outcomes of iontophoresis in a multiethnic group.

The association between body composition, 25(OH)D, and PTH and bone mineral density in black African and Asian Indian population groups.

CONTEXT AND OBJECTIVE: There are few data on the contribution of body composition to bone mineral density (BMD) in non-Caucasian populations. We therefore studied the contribution of body composition, and possible confounding of 25-hydroxyvitamin D and PTH, to BMD at various skeletal sites in black African (BA) and Asian Indian (AI) subjects. DESIGN AND SETTING: This was a cross-sectional study in Johannesburg, South Africa. PARTICIPANTS: BMD, body fat, and lean mass were measured using dual x-ray absorptiometry and abdominal fat distribution by ultrasound in 714 healthy subjects, aged 18-65 years. RESULTS: Whole-body (subtotal), hip, femoral neck, and lumbar spine (lumbar) BMD were significantly higher in BA than AI subjects (P < .001 for all). Whole-body lean mass positively associated with BMD at all sites in both ethnic groups (P < .001 for all) and partially explained the higher BMD in BA females compared with AI females. Whole-body fat mass correlated positively with lumbar BMD in BA (P = .001) and inversely with subtotal BMD in AI subjects (P < .0001). Visceral adiposity correlated inversely with subtotal BMD in the BA (P = .037) and with lumbar BMD in the AI group (P = .005). No association was found between serum 25-hydroxyvitamin D and BMD. PTH was inversely associated with hip BMD in the BA group (P = .01) and with subtotal (P = .002), hip (P = .001), and femoral BMD (P < .0001) in the AI group. CONCLUSIONS: Significant differences in whole-body and site-specific BMD between the BA and AI groups were observed, with lean mass the major contributor to BMD at all sites in both groups. The contribution of other components of body composition differed by site and ethnic group.

Fracture patterns and bone mass in South African adolescent-mother pairs: the Birth to Twenty cohort.

UNLABELLED: The associations of fracture prevalence and bone mass in adolescents with maternal fracture history and bone mass have not been investigated previously in South Africa. Maternal bone mass has a significant inverse association with their adolescents' fracture rates and bone mass across all ethnic groups. INTRODUCTION: Differences in fracture rates and bone mass between families and individuals of different ethnic origins may be due to differing lifestyles and/or genetic backgrounds. This study aimed to assess associations of fracture prevalence and bone mass in adolescents with maternal fracture history and bone mass, and sibling fracture history. METHODS: Data from 1,389 adolescent-biological mother pairs from the Birth to Twenty longitudinal study were obtained. Questionnaires were completed on adolescent fractures until 17/18 years of age and on sibling fractures. Biological mothers completed questionnaires on their own fractures prior to the age of 18 years. Anthropometric and bone mass data on adolescent-biological mother pairs were collected. RESULTS: An adolescent's risk of lifetime fracture decreased with increasing maternal lumbar spine (LS) bone mineral content (BMC; 24 % reduction in fracture risk for every unit increase in maternal LS BMC Z-score) and increased if they were white, male, or had a sibling with a history of fracture. Adolescent height, weight, male gender, maternal bone area and BMC, and white ethnicity were positive predictors of adolescent bone mass. White adolescents and their mothers had a higher fracture prevalence (adolescents 42 %, mothers 31 %) compared to the black (adolescents 20 %, mothers 6 %) and mixed ancestry (adolescents 20 %, mothers 16 %) groups. CONCLUSION: Maternal bone mass has a significant inverse association with their adolescent off-springs' fracture risk and bone mass. Furthermore, there is a strong familial component in fracture patterns among South African adolescents and their siblings.

Near infrared reactance for the estimation of body fatness in regularly exercising individuals.

Near infrared reactance (NIR) is used to measure body fat percentage (BF%), but there is little data on its use in non-obese, regularly exercising individuals. Therefore, this study aimed to examine the limits of agreement between NIR compared to dual x-ray absorptiometry (DXA) for the measurement of BF% in 2 cohorts of regularly exercising individuals. BF% was measured using DXA and NIR in a regular exercising (≥3 sessions/week), healthy active cohort (HA; n=57), and in a regularly exercising and resistance trained (≥2 sessions/week) cohort (RT; n=59). The RT cohort had lower BF% than the HA cohort (15.3±5.5% and 25.8±7.1%, P<0.001). In the HA and RT cohorts, NIR BF% was associated with DXA BF% (R2=0.72, SEE=3.7, p<0.001 and R2=0.50, SEE=4.1 p<0.001, respectively). In the HA cohort, NIR tended to under-predict BF% (mean difference: - 1.3%; 95% limits of agreement (LOA); - 8.8 to 6.2%) whereas in the RT cohort, NIR tended to over-predict BF% compared to DXA (mean difference: 1.1; 95% LOA; - 8.1 to 10.3%). In conclusion, NIR and DXA yield similar average BF% measurements in 2 cohorts of non-obese regularly exercising individuals. However, the rather broad LOA of NIR need to be considered when using NIR to screen for overweight and obesity, or measure and track changes in body composition.

Site-specific differences in bone mineral density in black and white premenopausal South African women.

SUMMARY: We examined ethnic differences in bone mineral density (BMD) and the contribution of body composition, lifestyle and socioeconomic factors in South African women. Femoral neck and total hip BMD were higher, but lumbar spine BMD was lower in black women, with body composition, lifestyle and socioeconomic status (SES) factors contributing differently in ethnic groups. INTRODUCTION: There is a paucity of data on the relative contribution of body composition, lifestyle factors and SES, unique to different ethnic groups in South Africa, to BMD. We examined differences in femoral neck (FN), total hip (TH) and lumbar spine (LS) BMD between black and white premenopausal South African women and the associations between BMD and body composition, lifestyle factors and SES in these two ethnic groups. METHODS: BMD and body composition were measured in 240 black (27 ± 7; 18-45 years) and 187 white (31 ± 8; 18-45 years) women using dual-energy X-ray absorptiometry. Questionnaires were administered to examine SES, physical activity and dietary intake. RESULTS: After co-varying for age, FN and TH were higher in black than white women (FN 0.882 ± 0.128 vs. 0.827 ± 0.116 g/cm(2), P < 0.001; TH 0.970 ± 0.130 vs. 0.943 ± 0.124 g/cm(2), P = 0.018). When adjusting for ethnic differences in body composition, LS was higher in white than black women. In black women, fat-free soft tissue mass, SES and injectable contraceptive use explained 33-42% of the variance in BMD at the hip sites and 22% at the LS. In white women, fat-free soft tissue mass and leisure activity explained 24-30% of the variance in BMD at the hip sites, whereas fat mass, leisure activity and oral contraceptive use explained 11% of the variance at the LS. CONCLUSION: FN and TH BMD were higher, but LS BMD was lower in black than white South African women with body composition, lifestyle and SES factors contributing differently to BMD in these women.

Association between infant nutrition and anthropometry, and pre-pubertal body composition in urban South African children.

Early life nutrition and growth are related to subsequent obesity risk in high-income countries. We investigated the association between nutrition and growth during infancy, and body composition at 10 years of age in 140 children selected from the Bone Health sub-study of the Birth-to-Twenty cohort from Soweto, Johannesburg, South Africa. Infant feeding and dietary data were collected during the first 12 months, and weight and height were measured at 1 and 2 years of age. At 10 years, anthropometry and dual-energy X-ray absorptiometry (DXA)-derived body composition were measured. Regression models were used to determine associations between independent and dependent variables at the 1% level of significance. A one z-score increase in birth weight was associated with a 1051 g increase in lean mass and a 0.22 increase in body mass index (BMI) z-score at the age of 10 years. After adjusting for confounders, stunting at age 1 year was associated with lower fat mass only at 10 years of age while at age 2 years, it was associated with lower lean mass only. Being underweight at one year of age was significantly associated with lower lean mass only. Weight-for-age (WAZ) change in the second year of infancy was a predictor of fat mass and BMI only. Body fatness at 10 years of age was positively associated with infant WAZ change rather than height-for-age change. There were no significant associations between infant dietary patterns, wasting and being underweight at age 2 years and pre-pubertal body composition. Further studies are needed to assess whether these associations continue during adolescence as pubertal development may be an important modifier of these associations.

Comparison of site-specific bone mass indices in South African children of different ethnic groups.

This study reports on ethnic differences in bone mass before and after adjusting for differences in body size and bone area (BA). Lumbar spine (LSBMC), proximal femur (PFBMC) and femoral neck (FNBMC) bone mineral contents were measured in black ('black'; n = 263) and white ('white'; n = 73) children from Johannesburg and children of mixed ancestral origin ('mixed'; n = 64) from Cape Town, South Africa. Geometric estimates and the power coefficient from the regression analyses of BMC on BA were calculated. After adjusting for age, weight, and height, LSBMC in girls and FNBMC in girls and boys were greatest in mixed, followed by black and then white, groups. Mixed boys and girls also had greater PFBMC than their black and white peers, but only in the boys was PFBMC greater in the black than the white groups. When including BA in the adjustment, differences remained at the FN in boys and girls, and the LS and PF in girls, but disappeared at the PF in mixed and black boys. The difference in LSBMC between mixed and black boys became significant after adjustment for age, weight, height, and BA. Geometric estimates at the femoral neck were greater in the mixed group. Power coefficients were greater in the white group, suggesting differences in shape or bone distribution. In conclusion, this study suggests that, in addition to differences in BMC, differences in bone strength and geometry are present which might confer advantages to the bone of mixed-ancestry children.

Early life and current determinants of bone in South African children of mixed ancestral origin.

BACKGROUND: The influence of early life factors on the bone mineral density of children has been identified, however the contribution of these determinants may vary. AIM: The study investigated determinants of bone mineral content (BMC) in South African children of mixed ancestral origin. SUBJECTS AND METHODS: Early life data including birth weight, maternal alcohol consumption and smoking during pregnancy were collected on 9-year-old children of mixed ancestral origin (n = 64). Grip strength was measured, and physical activity, housing density and dietary data were collected. Whole body BMC (WB BMC), fat-free soft tissue and fat tissue were measured using dual energy X-ray absorptiometry. RESULTS: Maternal alcohol consumption during pregnancy was associated with WB BMC, however after adjusting for possible confounders, this was no longer significant. When combined with gender, gestational age and maternal BMC in a multiple regression, maternal alcohol consumption during pregnancy could explain 20% of the variance in the WB BMC, however when current height was included in the model, the contribution of the other factors was insignificant. There was however a significant correlation between current height and birth weight (r = 0.34; p < 0.01) and alcohol consumption during pregnancy (r = 0.34; p < 0.05). A model consisting of current factors such as age, weight, gender, grip strength and calcium intake was able to explain 81.5% of the variance. Housing density was negatively correlated with WB BMC (r =-0.11; p = 0.05). CONCLUSION: These data suggest that although early life factors may contribute indirectly to the bone mass of children of mixed ancestral origin, the contribution of current factors is greater. In addition, environmental factors such as housing density have a direct effect on bone mass, independent of body size.