More than four in ten older Americans take five or more prescription drugs, and this study shows obesity may account for millions of those cases. Researchers say reducing obesity could help reduce drug burden in later life.
Study: Contribution of obesity to polypharmacy in older US adults. Image credit: Kotcha K/Shutterstock.com
A recent one Journal of General Internal Medicine The study examined whether obesity was associated with polypharmacy using a nationally representative sample of US older adults.
Obesity burdens medication in later life
Polypharmacy, broadly defined as the concurrent use of five or more medications by an individual, is particularly prevalent among the elderly. This widespread use of multiple medications is associated with a variety of negative outcomes, including adverse drug reactions, increased treatment burden, and reduced quality of life. Managing multiple medications can increase the likelihood of complex drug interactions, medication nonadherence, and a greater risk of harmful side effects. These challenges can significantly affect the health and daily functioning of older adults.
Obesity plays an important role in the development of chronic health conditions, including diabetes, hypertension, and cardiovascular disease, which often require ongoing pharmacological management. Consequently, people with obesity are at increased risk of polypharmacy compared to people without obesity. Despite this association, the specific contribution of obesity to the prevalence of polypharmacy among the elderly remains unclear and requires further investigation.
The national survey looked at obesity and medication use
The current cross-sectional analysis used data from the 2021–2023 National Health and Nutrition Examination Survey (NHANES). Adults over 65 years of age with a body mass index (BMI) ≥ 18.5 kg/m² were included. All participants with missing data on BMI or medication use were excluded.
Obesity, defined by BMI (≥ 30 kg/m²) or waist circumference (≥ 102 cm in men, ≥ 88 cm in women) and obesity category (category 1: BMI 30–<35 kg/m²; category 2–4: BMI ≥ 35 kg/m² as independent variable). Polypharmacy, defined as the self-reported use of five or more prescription drugs, was the dependent variable.
Groups with and without obesity were compared for demographic and clinical characteristics using χ² and t-test. Logistic regression estimated the adjusted relative risk of polypharmacy among obese subjects defined by BMI, adjusting for baseline covariates. The population attributable fraction (PAF) of polypharmacy due to obesity was calculated using the adjusted relative risk and prevalence of obesity, with additional PAF values determined for obesity category and waist circumference.
Obesity was associated with a higher prevalence of polypharmacy
The study included 1,944 participants, representing approximately 53.2 million older adults in the US, with an average age of 72.7 years. Just over half were women, and the sample reflected the racial and ethnic diversity of the US elderly population.
Polypharmacy was common, affecting 41.8% of participants, equivalent to approximately 22 million seniors nationwide. Obesity was also widespread: nearly 39% of participants were obese based on BMI, while more than 70% met the definition based on waist circumference.
Older adults with BMI-defined obesity were significantly more likely to experience polypharmacy than those without obesity, with prevalence rates of 51.1% and 35.9%, respectively. Based on these findings, the researchers estimated that approximately 3.3 million cases of polypharmacy, or 14.8% of all cases among the elderly, were attributable to BMI-defined obesity.
The estimated contribution varied by definition and severity of obesity. Class I obesity accounted for 4.9% of polypharmacy cases, while class II-IV obesity accounted for 9.7%. When obesity was defined using waist circumference, the estimated attributable fraction increased to 24.8%, suggesting that central obesity may have an even stronger association with polypharmacy than BMI alone.
The authors highlighted several limitations of the current study, including potential errors in self-reported medication data and the exclusion of long-term care residents, which reduce generalizability. Countless confounding factors, such as socioeconomic status or access to health care, may affect the results. Subgroup differences in PAF were not investigated.
The cross-sectional design further limits causal inferences, although longitudinal studies support an association between obesity and polypharmacy. However, given the study’s findings, the researchers believe that targeted strategies to address obesity could potentially reduce polypharmacy and improve health outcomes in older adults.
Obesity may be a modifiable driver of polypharmacy
Overall, the findings suggest that obesity, particularly abdominal obesity as measured by waist circumference, is associated with a significantly higher likelihood of polypharmacy in older adults. Depending on how obesity was defined, it was estimated to account for one in seven to one in four cases of polypharmacy, highlighting obesity as a potentially modifiable factor in medication burden, although the cross-sectional study cannot establish cause and effect.
Treating obesity may reduce medication burden, but weight loss medications should be carefully considered given their potential to relieve and add to polypharmacy by directly increasing medication burden and side effects. Assessing the impact of obesity treatments on overall medication use requires further study.
