• Shaoyuan Wang, Jean-Luc Kortenaar, Mark W Hull, Gordon Arbess, James Rm Owen, and Darrell Hs Tan.
• Division of Infectious Diseases, St Michael's Hospital, Toronto, ON, Canada, darrell.tan@gmail.com.
• Patient Prefer Adher. 2018 Jan 1; 12: 2197-2204.

BackgroundDaily tenofovir disoproxil fumarate (TDF)/emtricitabine as HIV pre-exposure prophylaxis (PrEP) causes subclinical decreases in bone mineral density (BMD). We surveyed PrEP users to assess feasibility for a clinical trial of vitamin D supplementation to mitigate TDF-induced BMD loss.MethodsWe recruited participants using or starting PrEP in Toronto and Vancouver. The primary objective was to assess the acceptability of daily or weekly vitamin D supplementation. We also assessed the acceptability of calcium supplementation, existing use of non-pharmacological bone health interventions, prevalence of osteoporosis risk factors, and bone health knowledge (Osteoporosis Knowledge Test, OKT).ResultsOf 161 participants, 72.1% were current PrEP users, 18.0% were starting PrEP, and 9.9% did not indicate their PrEP status. All identified as males, 88.8% as gays, and 67.1% as Whites. Median (IQR) age was 32.0 (29.0, 40.0) years, and 62.1% reported family income $$60,000/year. Among those not already using the interventions, willingness to supplement with daily vitamin D, weekly vitamin D, or daily calcium was very high at 90.9%, 96.4%, and 93.0 %, respectively. Only 31.0% reported adequate dietary calcium intake, while 42.9% reported $1 osteoporosis risk factor (most commonly, alcohol and smoking). Overall bone health knowledge was low, as median (IQR) OKT score was 16/32. In post hoc comparisons, current PrEP users may have been more likely than new PrEP users to engage in bone loading exercise (Bone-specific Physical Activity Questionnaire score=12.5 vs 3.6, P=0.001) and have greater bone health knowledge (OKT=17 vs 14, P=0.08), but they had similar levels of current vitamin D supplementation (37.4% vs 21.4%, P=0.11), calcium supplementation (11.2% vs 13.8%, P=0.70), and adequate dietary calcium intake (32.7% vs 25.0%, P=0.43).DiscussionThe high acceptability of vitamin D and calcium supplementation in this cohort suggests that enrollment into a clinical trial of such interventions to mitigate PrEP-induced BMD loss is feasible.

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