Concurrent use of drugs and supplements in a community-dwelling population aged 50 years or more: potential benefits and risks.

BACKGROUND: The use of vitamin and mineral (VMs) and non-vitamin/non-mineral supplements (non-VMs) in the general population and the older population in developed countries has increased. When combined with drugs, their use can be associated with benefit and potential risks.
OBJECTIVE: The aims of this study were to determine the extent and associated factors of the combined use of drugs and VM/non-VM supplements, and to examine the potential major drug-supplement interactions
METHODS: Cross-sectional analysis of first-wave data of TILDA, The Irish Longitudinal Study on Ageing, nationally representative a cohort including 8,081 community-dwelling persons aged ≥50 years. Prevalences including 95 % confidence intervals (CI) were weighted to the population. Group differences in drug and supplement use were assessed using Pearson's Chi-square test, and associations between concurrent drug-supplement use and covariates were assessed using logistic regression. Potential interactions between drugs and supplements were assessed using relevant sources.
RESULTS: Every seventh respondent (14.0 %; 95 % CI 13.1-15.0) reported regular concurrent use of drugs and supplements; 7.9 % (95 % CI 7.3-8.6) took only VMs, 3.9 % (95 % CI 3.4-4.4) took only non-VMs, and 2.2 % (95 % CI 1.8-2.6) took at least one of each concurrently with drugs. Concurrent use was more prevalent in women and in the oldest (≥75 years) group. Chronic disease, female sex, third-level education and private medical insurance were associated with an increased likelihood of use of both supplement types, whereas those classed as employed were much less likely to use any supplements. Supplements were combined with drugs in all of the commonly prescribed therapeutic groups, ranging from just under 60 % with drugs for bone diseases to 15.7 % with drugs for diabetes. Potential major drug-supplement interactions were detected in 4.5 % (95 % CI 3.4-5.8) of concurrent drug-supplement users, and were more prevalent in older respondents.
CONCLUSIONS: Concurrent use of drugs and supplements among those aged over 50 years in the Irish population is substantial and increases with age. There is considerable variation in usage, and the outcome of this approach is evidence of unmet need and therefore unrealised benefits among some subgroups, and of exposure to avoidable and potential serious drug interactions among others.