More than four in ten older Americans take five or more prescription medications, and this study suggests obesity may account for millions of those cases. Researchers say reducing obesity could help lower medication burden in later life.
Study: Contribution of Obesity to Polypharmacy in U.S. Older Adults. Image credit: Kotcha K/Shutterstock.com
A recent Journal of General Internal Medicine study examined whether obesity was associated with polypharmacy using a nationally representative sample of U.S. older adults.
Obesity adds to medication burden in later life
Polypharmacy, broadly defined as the concurrent use of five or more medications by an individual, is highly prevalent among older adults. This widespread use of multiple medications is linked to a variety of negative outcomes, such as adverse drug events, increased treatment burden, and diminished quality of life. Managing numerous medications can increase the likelihood of complex drug interactions, medication nonadherence, and a greater risk of harmful side effects. These challenges can substantially affect the health and daily functioning of older people.
Obesity plays a significant role in the development of chronic health conditions, including diabetes, hypertension, and cardiovascular disease, that frequently require ongoing pharmacologic management. Consequently, individuals with obesity are at an elevated risk for polypharmacy compared to those without obesity. Despite this association, the specific contribution of obesity to polypharmacy prevalence among older adults remains unclear and warrants further investigation.
National survey examined obesity and medication use
The current cross-sectional analysis utilized data from the 2021–2023 National Health and Nutrition Examination Survey (NHANES). Adults aged over 65 years with body mass index (BMI) ≥ 18.5 kg/m² were included. Any 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 class (class 1: BMI 30–<35 kg/m²; class 2–4: BMI ≥ 35 kg/m²) served as independent variables. Polypharmacy, defined as self-reported use of five or more prescription medications, was the dependent variable.
Groups with and without obesity were compared on demographic and clinical characteristics using χ² and t-tests. Logistic regression estimated the adjusted relative risk of polypharmacy among BMI-defined obese individuals, adjusting for key covariates. The population attributable fraction (PAF) of polypharmacy due to obesity was calculated using the adjusted relative risk and obesity prevalence, with additional PAF values determined for obesity class and waist circumference.
Obesity was linked to higher polypharmacy prevalence
The study included 1,944 participants, representing an estimated 53.2 million U.S. older adults, with an average age of 72.7 years. Just over half were women, and the sample reflected the racial and ethnic diversity of the older U.S. population.
Polypharmacy was common, affecting 41.8% of participants, equivalent to approximately 22 million older adults nationwide. Obesity was also widespread: nearly 39% of participants had obesity based on BMI, while more than 70% met the definition based on waist circumference.
Older adults with BMI-defined obesity were considerably 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 around 3.3 million cases of polypharmacy, or 14.8% of all cases among older adults, were attributable to BMI-defined obesity.
The estimated contribution varied according to the 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. Unmeasured confounders, such as socioeconomic status or healthcare access, might influence results. Subgroup differences in PAF were not explored.
The cross-sectional design further limits causal conclusions, though longitudinal studies support an association between obesity and polypharmacy. However, given the study's findings, 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 measured by waist circumference, is associated with a substantially higher likelihood of polypharmacy in older adults. Depending on how obesity was defined, it accounted for an estimated one in seven to one in four polypharmacy cases, highlighting obesity as a potentially modifiable contributor to medication burden, although the cross-sectional study cannot establish cause and effect.
Addressing obesity may reduce medication burden, but weight loss medications should be considered carefully, given their potential to both alleviate and add to polypharmacy through an immediate increase in medication burden and side effects. Evaluating the impact of obesity treatments on overall medication use warrants further study.
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