A pilot investigation of load-carrying on the head and bone mineral density in premenopausal, black African women

Osteoporosis in Africa-where are we now

Africa is experiencing an exponential increase in the number of older persons. The number of persons surviving with human immunodeficiency virus is simultaneously increasing due to improved availability of anti-retroviral therapy. The burden of non-communicable diseases, in particular, osteoporosis and its consequent fragility fractures, is also predicted to increase. Osteoporosis, however, remains a neglected disease and there are no age-standardized reference data available to accurately screen and diagnose individuals with osteoporosis. Epidemiological studies reporting the incidence of hip fracture or vertebral fractures are limited from Africa, especially Sub-Saharan Africa. The studies are usually limited as they are based on a retrospective data and small study numbers and often from a single study site. However, compared with early initial studies, the more recent studies show that osteoporosis and fractures are increasing across the continent. The overall incidence rates for osteoporosis and fractures still vary greatly between different regions in Africa and ethnic groups. Predisposing factors are similar with those in developed countries, but awareness of osteoporosis is sorely lacking. There is a lack of awareness among the population as well as health authorities, making it extremely difficult to quantify the burden of disease. There is great potential for research into the need and availability of preventive strategies. The FRAX® tool needs to be developed for African populations and may circumvent the shortage of bone densitometry.

Bone health of the Ovahimba people of north-western Namibia in the context of urbanization and a change of the sociocultural environment

The prevalence of osteoporosis in Sub-Saharan African (SSA) countries is low, however, as urbanization takes root, it is predicted that bone health will decrease dramatically. The bone health of the semi-nomadic Ovahimba people of Namibia was investigated in the context of urbanization and changes of the sociocultural environment. Furthermore, data on bone health in SSA countries is scarce; there exists no ethnic-specific reference group for people of black origin. Included in the study were 98 urban and rural living Ovahimba people. Quantitative ultrasound was performed, sunrise/sunset saliva cortisol concentrations was measured and a questionnaire was conducted. There was no significant difference in the QUS parameters, however, after adjustment for confounders, SOS and SI differed significantly. The saliva cortisol concentrations differed significantly. After adjustment for confounders, saliva cortisol was significantly negatively correlated to SOS (r= -0.27, p = 0.021) giving an indication for an association between cortisol concentration and QUS parameters. The urban group furthermore showed a nutritional transition. Even though the bone health of the Ovahimba is very good, first signs of the adverse effects of urbanization were detected. Beside changes of lifestyle, this may be attributed to an increased cortisol exposure of the Ovahimba people living in an urban environment due to an increased psychosocial stress.

Lean Mass Appears to Be More Strongly Associated with Bone Health than Fat Mass in Urban Black South African Women

OBJECTIVES

To examine the association between body composition (fat mass, lean mass and body mass index, BMI) and bone health (bone mineral density, BMD and fracture risk) in urban black South African women.

DESIGN

A cross sectional study examining associations between body composition, dietary intake (food frequency questionnaire), habitual physical activity (Activity energy expenditure (AEE) measured using an accelerometer with combined heart rate monitor and physical activity questionnaire) and bone health (BMD using dual-energy X ray absorptiometry, DXA and fracture risk).

SETTING

Urban community dwellers from Ikageng in the North-West Province of South Africa.

PARTICIPANTS

One hundred and eighty nine (189) healthy postmenopausal women aged ≥43 years.

RESULTS

Fat mass and lean mass were significantly associated with BMD and fracture risk when adjusted for potential confounders. However, lean mass and not fat mass remained significantly associated with femoral neck BMD (β = 0.49, p <0.001), spine BMD (β = 0.48, p< 0.0001) and hip BMD (β = 0.59, p< 0.0001). Lean mass was also negatively associated with fracture risk (β = -0.19 p =0.04) when both lean and fat mass were in the same model.

CONCLUSION

Lean mass and fat mass were positively associated with femoral neck, spine and hip BMDs and negatively associated with fracture risk in urban black South African women. Our finding suggests that increasing lean mass rather than fat mass is beneficial to bone health. Our study emphasises the importance of positive lifestyle changes, intake of calcium from dairy and adequate weight to maintain and improve bone health of postmenopausal women.

Factors associated with bone mineral density in healthy African women

There is a paucity of normative bone mineral density (BMD) data in healthy African women. Baseline total hip and lumbar spine BMD was measured in premenopausal women. BMD distribution was comparable to that of a reference population and was impacted by several factors including contraception and duration of lactation.

INTRODUCTION

Normative data on bone mineral density (BMD) and the cumulative impact of lactation, contraceptive use, and other factors on BMD in healthy African women have not been well studied.

OBJECTIVES

The objective of this study was to determine the factors associated with BMD in healthy premenopausal women in Uganda and Zimbabwe.

METHODS

Baseline total hip (TH) and lumbar spine (LS) BMD was measured by dual x-ray absorptiometry in 518 healthy, premenopausal black women enrolling in VOICE, an HIV-1 chemoprevention trial, at sites in Uganda and Zimbabwe. Contraceptive and lactation histories, physical activity assessment, calcium intake, and serum vitamin D levels were assessed. Independent factors associated with BMD were identified using an analysis of covariance model.

RESULTS

The study enrolled 331 women from Zimbabwe and 187 women from Uganda. Median age was 29 years (IQR 25, 32) and median body mass index (BMI) was 24.8 kg/m(2) (IQR 22.2, 28.6). In univariate analyses, lower TH BMD values were associated with residence in Uganda (p < 0.001), lower BMI (p < 0.001), and any use of and duration of depot-medroxyprogresterone acetate. Use of oral contraceptives, progestin-only implants, and higher physical activity levels were protective against reduced BMD. Similarly, lower LS BMD values were associated with these same factors but also higher parity and history of breastfeeding. In a multivariable analysis, lower TH and LS BMD values were associated with enrollment in Uganda, lower BMI, and lower physical activity level; contraceptive use was associated with lower spine BMD, and breastfeeding contributed to lower total hip BMD.

CONCLUSIONS

Among healthy premenopausal women, TH and LS BMD was higher in Zimbabwe than Uganda. Additional factors independently associated with BMD included BMI, physical activity level, contraceptive use, and lactation.

Urbanization of black South African women may increase risk of low bone mass due to low vitamin D status, low calcium intake, and high bone turnover

Globally, rural to urban migration is accompanied by changes in dietary patterns and lifestyle that have serious health implications, including development of low bone mass. We hypothesized that serum 25 (OH) vitamin D3 (25[OH]D3) levels will be lower, bone turnover higher, and nutrition inadequate in urban postmenopausal black women, increasing risk for low bone mass. We aimed to assess the prevalence of risk factors for low bone mass in 1261 black women from rural and urban areas in the North West Province of South Africa (Prospective Urban and Rural Epidemiology-South Africa project). Fasting blood samples were taken; and participants were interviewed to complete questionnaires on self-reported diseases, fractures, and dietary intakes. Bone health markers were assessed in a subgroup of 658 women older than 45 years. Specific lifestyle risk factors identified were inactivity, smoking, injectable progestin contraception use, and high alcohol consumption. Dietary risk factors identified were low calcium and high animal protein, phosphorous, and sodium intakes. The 25(OH)D3 and C-terminal telopeptide (CTX) levels were significantly higher in the rural vs the urban women older than 50 years. Parathyroid hormone (PTH) levels increased with age in both groups. The 25(OH)D levels were inversely correlated with CTX and PTH in rural women. In urban women, PTH and CTX were correlated while dietary calcium was inversely correlated with CTX and PTH with 25(OH)D3. The combination of low dietary calcium (<230 mg/d), marginally insufficient 25(OH)D3 status, and raised PTH may result in increased bone resorption. Further research is required to assess bone health and fracture risk in black African women.

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.

A kinetic comparison of back-loading and head-loading in Xhosa women

The purpose of this study was to compare the kinetic responses associated with ground reaction force measurements to both head-loading and back-loading in a group of Xhosa women. Altogether, 16 women were divided into two groups based on their experience of head-loading. They walked over a force plate in three conditions: unloaded or carrying 20 kg in either a backpack or on their head. The most striking finding was that there was no difference in kinetic response to head-loading as a consequence of previous experience. Considering the differences between the load carriage methods, most changes were consistent with increasing load. Head-loading was, however, associated with a shorter contact time, smaller thrust maximum and greater vertical force minimum than back-loading. Both loading conditions differed from unloaded walking for a number of temporal variables associated with the ground contact phase, e.g. vertical impact peak was delayed whilst vertical thrust maximum occurred earlier. STATEMENT OF RELEVANCE: Consideration of the kinetics of head and back load carriage in African women is important from a health and safety perspective, providing an understanding of the mechanical adaptations associated with both forms of load carriage for a group of people for whom such load carriage is a daily necessity.