Inappropriate vitamin D supplementation among multimorbid older patients: a multicountry analysis.

Background: The prevalence of vitamin D supplementation and the percentage of participants with a lack of appropriate vitamin D supplementation ("potential underuse") or potentially inappropriate vitamin D supplementation ("potential overuse") and risk factors for these are currently unclear.

Methods: Cross-sectional analysis from the OPERAM study, a multicenter cluster randomized controlled trial in four European countries (Belgium, Ireland, The Netherlands, Switzerland) including multimorbid (≥ 3 chronic conditions) older patients, with polypharmacy (≥ 5 chronic medications). For the definition of potential underuse and overuse we used high-risk conditions, which were defined according to the START criteria (version 2) for potential prescribing omissions in older people i.e., E2) long-term systemic corticosteroid therapy, known osteoporosis or osteopenia, E3) previous fragility fractures, and E5) housebound/in nursing homes or experiencing falls. We used mixed effect logistic regression to identify factors associated with underuse and overuse.

Results: 2008 patients (79.4y, SD 6.3, 45% female) were included. 825/2008 (41.1%) were supplemented with vitamin D. We identified 681 participants with potential underuse (33.9% of all participants, 69.7% of non-vitamin D users) and 204 with potential overuse (10.2% of all participants, 24.7% of vitamin D users). In the multivariable logistic regression analysis increasing age and being male were associated with underuse, while the number of baseline medications and previous hospitalizations were associated with both underuse and overuse. Specifically, underuse decreased with an increasing number of medications (OR: 0.93, 95% CI: 0.90-0.95), while overuse increased (OR: 1.08, 95% CI: 1.04-1.12). Previous hospitalizations were linked to underuse (OR: 1.08, 95% CI: 1.00-1.17) and inversely associated with overuse (OR: 0.88, 95% CI: 0.77-0.99).

Conclusions: One-third of multimorbid older adults experienced potential underuse, while up to 10% potential overuse of vitamin D supplementation. Polypharmacy, previous hospitalizations, increasing age and being male are factors associated with inappropriate use of vitamin D. A better targeted vitamin D supplementation is warranted.

Trial registration: NCT02986425, Registration date 2016-10-21.