More than 4 in 10 older Americans take five or more prescription drugs, and the study suggests that millions of these may be due to obesity. Researchers say reducing obesity may help reduce medication burden later in life.
Study: Contribution of obesity to polypharmacy in older adults in the United States. Image credit: Kotcha K/Shutterstock.com
recent General Internal Medicine Journal The study investigated whether obesity was associated with polypharmacy in a nationally representative sample of older Americans.
Obesity increases drug burden later in life
Polypharmacy, broadly defined as the simultaneous use of five or more drugs by an individual, is highly prevalent among older adults. This widespread use of multiple drugs is associated with a variety of negative outcomes, including adverse drug events, increased treatment burden, and decreased quality of life. Managing a large number of medications can increase the risk of complex drug interactions, nonadherence, and adverse side effects. These challenges can have a significant impact on the health and daily life of older adults.
Obesity plays an important role in the development of chronic health conditions such as diabetes, hypertension, and cardiovascular diseases, which often require ongoing pharmacological management. As a result, people with obesity have a higher risk of polypharmacy than people without obesity. Despite this association, the specific contribution of obesity to the prevalence of polypharmacy in older adults remains unclear and requires further investigation.
National survey investigating obesity and drug use
The current cross-sectional analysis utilized data from the 2021-2023 National Health and Nutrition Examination Survey (NHANES). Adults aged 65 years and older and body mass index (BMI) ≥18.5 kg/m² were included. Participants with missing data on BMI or drug use were excluded.
Obesity defined by BMI (≥ 30 kg/m²) or waist circumference (≥ 102 cm for men and ≥ 88 cm for women), and obesity class (class 1: BMI 30 to <35 kg/m², class 2 to 4: BMI ≥ 35 kg/m²) served as independent variables. Polypharmacy, defined as self-reported use of five or more prescription drugs, was the dependent variable.
Groups with and without obesity were compared with respect to demographic and clinical characteristics using χ² and t tests. Logistic regression estimated the adjusted relative risk of polypharmacy in obese individuals defined by BMI, adjusting for key covariates. The population attributable fraction (PAF) of polypharmacy due to obesity was calculated using adjusted relative risk and obesity prevalence, and additional PAF values were determined for obesity class and waist circumference.
Obesity was associated with higher rates of polypharmacy
The study included 1,944 participants, representing an estimated 53.2 million older adults in the United States, with an average age of 72.7 years. Just over half were women, and the sample reflected the racial and ethnic diversity of older adults in the United States.
Polypharmacy is common, affecting 41.8% of participants, representing approximately 22 million older adults nationwide. Obesity was also prevalent, with approximately 39% of participants being obese based on BMI, while more than 70% met the definition based on waist circumference.
Older adults with obesity defined by BMI were significantly more likely to experience polypharmacy than older adults 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 in older adults, were attributable to obesity as defined by BMI.
The estimated contribution depends on the definition and severity of obesity. Class I obesity accounted for 4.9% of polypharmacy cases, and class II-IV obesity accounted for 9.7%. When using waist circumference to define obesity, the estimated contribution 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 patients, which reduces generalizability. Unmeasured confounders such as socio-economic status and healthcare access may influence the results. Subgroup differences in PAF have not been investigated.
Although longitudinal studies support an association between obesity and polypharmacy, cross-sectional designs further limit causal conclusions. However, given the study results, researchers believe that targeted strategies to address obesity may reduce polypharmacy and improve health outcomes in older adults.
Obesity may be a modifiable factor in 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 is defined, obesity accounts for an estimated 1 in 7 to 1 in 4 polypharmacy cases, highlighting obesity as a potentially modifiable factor in drug burden, although cross-sectional studies cannot establish cause and effect.
Although addressing obesity may reduce medication burden, weight loss drugs must be carefully considered as they may alleviate or even increase polypharmacy through an immediate increase in medication burden and side effects. Further research is needed to assess the impact of obesity treatment on overall drug use.
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