IMPACT OF WEIGHT-BEARING AND SEX-STRATIFIED DIFFERENCES IN RISK FACTORS OF BONE LOSS ON BONE MINERAL DENSITY IN HIV CONDITIONS

S.C. Ibeneme^1,2,3,4, F. Fortwengel⁵, I.J. Okoye⁶, W.O. Okenwa⁷, A.D. Ezuma⁸, A.O. Nwosu⁹, G.C. Ibeneme¹⁰, A. Nnamani⁶, D. Limaye¹¹, F. Fneish¹², H. Myezwa², P. Okere⁶, N. Iloanusi⁶, A.T. Ajidahun², I. Ulasi¹³

¹Enugu State University Teaching Hospital, Parklane, Department of Physiotherapy, Enugu, Nigeria, ²University of the Witwatersrand, Department of Physiotherapy, Johannesburg, South Africa, ³University of Nigeria, Enugu Campus, Clinical Trial Consortium Research Group, Enugu, Nigeria, ⁴David Umahi Federal University of Health Sciences, Department of Physiotherapy, Enugu, Nigeria, ⁵Hochschule Hannover University, Faculty III, Hannover, Germany, ⁶University of Nigeria, Enugu Campus, Department of Radiation Medicine, Enugu, Nigeria, ⁷Enugu State University Teaching Hospital, Department of Surgery, Enugu, Nigeria, ⁸University of Nigerian Teaching Hospital, Department of Physiotherapy, Enugu, Nigeria, ⁹University of Nigeria, Enugu Campus, Department of Medical Rehabilitation, Enugu, Nigeria, ¹⁰Ebonyi State University, Department of Nursing Sciences, Abakaliki, Nigeria, ¹¹Puranik Society, Indianik Society, 7A4-602, Aldea Espanola, Maharashtra, India, ¹²Gottfried Wilhelm Leibniz Universität Hannover, Department of Biostatistics, Lagos, Nigeria, ¹³University of Nigeria, Enugu Campus, Department of Medicine, Enugu, Nigeria

Background: Sex differences in bone loss associated with human immune deficiency virus (HIV) and highly antiretroviral therapy (HAART) are physiologically plausible. Similarly, bone mineral density (BMD) variations in weight-bearing and non-weight-bearing bones due to osteogenic stimulus from biomechanical loading, could modulate sex and HIV-related BMD changes and should be explored.

Purpose: To i. Assess the variations in the BMD of weight-bearing (BMD_toe) and non-weight-bearing bones (BMD_thumb) in PLWH, ii. Determine the sex-stratified differences in BMD in relation to some risk factors of bone loss (age, height, weight, BMI, drug duration and type of drug and duration of HIV) in weight-bearing and non-weight-bearing bones.

Methods: A cross-sectional observational study of 503 people living with HIV (PLWH) selected by convenience sampling at Enugu State University Teaching Hospital, Nigeria, was conducted from September 2015 to September 2016. The BMD of toe or weight-bearing (BMD_toe) and thumb or non-weight-bearing (BMD_thumb) bones were measured with Xrite 331C densitometer and compared using independent t-test. Impact of the risk factors (age, weight, body mass index-BMI, duration of HIV, height and types of HAART) of bone loss and their relationships with the BMD were compared across the sexes using multivariate, and univariate regression analyses, at p<0.05, two-tailed.

Results: Females were 378/75.1%, with 89/17.7% males and 36/7.16% without gender specificity. Participants’ mean age=37.2±9.79years, and BMI=25.6±5.06kg/m². HAART-experienced participants were 352 (69.98%), and the duration of HAART exposure=4.54±3.51years. BMD_thumb (-0.93±0.44g/cm³) was lower (p<0.05) than BMD_toe (-0.16±0.65g/cm³), and BMD_toe differed across the BMI classes (p=0.000003;d=0.998), and which difference was accounted for in post hoc analysis by normal weight versus underweight BMI classes (p=<0.001). BMD_toe was positively correlated with height (r=0.13,r²=0.0169;p<0.05), and males were taller than females (p<0.001). Females accounted for 90% (9/10) and 71.43% (5/7) cases of osteopenia and osteoporosis, respectively. Males were older (p=0.002) while the females had greater BMI (p=0.02), lower median BMD_toe (p=0.005) and BMD_thumb (p=0.005).

Conclusions: Higher BMD in weight-bearing bones could be linked to osteogenic stimulus from loading. The association of underweight (sub-optimal loading) with lower BMD_toe reinforces this view and suggests a role for fat metabolism derangement in bone loss. Females being younger and heavier, would have more significant loading and osteogenic stimulus which could be strengthened by lesser age-related BMD changes. Males being taller would have greater bone marrow adipose tissue, promoting osteogenesis through paracrine mechanisms. Therefore, higher BMD in males than females should be explained by height-related metabolic surrogates and sex-hormonal differences. Greater BMD in females’ weight-bearing than non-weight-bearing bones implies that loading ameliorates physiological tendencies towards lower BMD.

Implications: Significantly higher BMD and non-oocurrence of osteopenia/osteoporosis in weight-bearing than non-weight-bearing bones suggest that biomechanical loading of the musculature could have a plausible role in the prevention of bone loss in HIV conditions. PLWH of the female sex and/or with low BMI could be at greater risk of lower BMD and should be monitored. Though height was positively related to the BMD, it only accounted for a small proportion of variance (1.69 %) implying that it is not of clinical significance.

Funding acknowledgements: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors

Keywords:
HIV
weight-bearing
bone mineral density

Topics:
Oncology, HIV & palliative care
Musculoskeletal
Health promotion & wellbeing/healthy ageing/physical activity

Did this work require ethics approval? Yes

Institution: University of Nigeria, Nsukka

Committee: University of Nigeria Health Research Ethics Committee

Ethics number: NHREC/05/01/2008B