This study aimed to examine the trends and determinants of dietary supplement use and to assess the prevalence and predictors of potential drug-supplement interactions among older adults over a 16-year follow-up. This repeated cross-sectional study included adults aged ≥ 50 years who participated in the third (2006–2008; n = 3,484), fourth (2009–2011; n = 4,020), fifth (2012–2014; n = 4,342), sixth (2015–2017; n = 4,598), and seventh (2018–2022; n = 4,750) examinations of the Tehran Lipid and Glucose Study (TLGS). Information on dietary supplement use, including individual vitamin supplements and prescription medication use was collected using standardized questionnaires. Trends in supplement use and participant characteristics were evaluated across study phases. Clinically relevant mild-to-moderate potential drug-supplement interactions were defined as the concurrent use of specific dietary supplements and commonly prescribed medications and were classified according to Stockley’s framework. Multivariable logistic regression models were used to identify factors associated with dietary supplement use and potential drug-supplement interactions in the 2018–2022 examination. Over 16 years, dietary supplement use increased more than 2-fold from 10.4% to 21.1%, mainly from increases in thiamin (2.2% to 13.4%), cobalamin (1.8% to 9.8%), vitamin C (1.3% to 7.9%), vitamin E (1.8% to 8.7%), and zinc (0.2% to 3.3%). Female sex, higher education, and diabetes were associated with higher likelihood of supplement use. In 2018–2022, 4.8% of participants had potential drug-supplement interactions, most commonly vitamin E with aspirin (2.3%) and magnesium or potassium with antihypertensive medications. The likelihood of potential drug-supplement interactions was higher in women (OR = 2.03, 95%CI = 1.61–2.56), participants with primary education (OR = 1.45, 95% CI = 1.09–1.96), smokers (OR = 1.50, 95%CI = 1.07–2.12), and individuals with diabetes (OR = 2.80, 95%CI = 2.13–3.68), hypertension (OR = 2.20, 95%CI = 1.78–2.73), chronic kidney disease (OR = 2.35, 95%CI = 1.88–2.94), or multimorbidity (OR = 2.46, 95%CI = 1.85–3.26). Over 16 years, supplement use increased among older adults, especially B-complex vitamins, vitamin C, vitamin E, and zinc, with a low but clinically relevant prevalence of drug-supplement interactions.
Bahadoran et al. (Fri,) studied this question.