The use of unnecessary and/or potentially harmful medications is a serious problem in older adults. Four out of ten adults 65 years and older take medications which do not provide much benefit or have significant side effects.(1) Polypharmacy – the daily use of multiple prescription and non-prescription medications to manage several chronic diseases – is a related concern. Forty percent of older American adults take 5 or more medications daily,(2) increasing their risk for adverse drug reactions such as falls, bleeding, hospitalizations, and death.(3) Concerns about polypharmacy and its adverse outcomes has led to the recent development of quality measures such as the 2022 Healthcare Effectiveness Data and Information Set (HEDIS) benzodiazepine deprescribing measure.(4) HEDIS measures are used by more than 90% of U.S. health plans.(5) Inclusion of deprescribing measures in quality measure sets reflects an increasing recognition by health system and insurance leaders of the importance of carefully monitoring potentially inappropriate medication use and implementing interventions to manage this clinical issue.
Deprescribing, or stopping or tapering potentially inappropriate medications, has been hypothesized to improve quality of life, to reduce falls and fall-related hospitalizations, and reduce healthcare utilization in older adults.(6) However, the evidence on deprescribing interventions for community-based older adults has been mixed.(7) A systematic review and meta-analysis found comprehensive medication reviews may result in small reductions in mortality (OR: 0.74, 95% CI: 0.58–0.95), but found no effects from other types of deprescribing interventions,(8) and found no clear delineating of which patients would benefit the most. Additionally, the review found no significant effects of deprescribing interventions on hospitalizations or emergency department (ED) visits – outcomes important to health systems, older adults, and payors.(8)
As deprescribing medications can be time consuming and challenging, researchers have noted an important gap in identifying which patients would most benefit from deprescribing.(9, 10) With limited resources available to address polypharmacy among community-dwelling adults in the primary care setting, physicians, pharmacists, and health system managers have to prioritize which patients should receive various intensities of deprescribing interventions.(10) These could include, at the least intensive level, a comprehensive annual medication review by a pharmacist or clinical decision support advising discontinuation, and at the most intensive level, enrollment in a deprescribing clinic with multiple follow-up visits. While prior studies have used markers for identifying older adults at high risk of polypharmacy-related adverse events such as the number of medications taken every day (e.g., ≥ 5 or ≥ 10 medications), adding additional clinical data such as renal, liver, and cognitive function; comorbidities, age, and other risk factors could make for more precise patient selection for deprescribing interventions. Moreover, combining clinical data with social determinants of health, such as dual eligibility for Medicare-Medicaid, Limited English Proficiency (LEP), living status (e.g., living alone), could help to identify older adults with polypharmacy who have additional need for medication-related support.
Risk prediction models in medicine have been used for allocations to a variety of interventions, including models aimed at identifying individuals at higher risk of breast cancer for referral to genetic counseling,(11) screening patients for lung cancer,(12, 13) assessing risk of stroke for provision of lifestyle interventions,(14) targeting patients at high risk of suicide,(15) and identifying hospitalized patients at high risk of delirium for intervention.(16) Several risk prediction models have been developed for predicting adverse drug reactions and hospitalizations for adverse drug events.(17–21) A 2014 systematic review identified four models aimed at predicting adverse drug events (ADEs) or adverse drug reactions (ADRs), finding several limitations of the existing models, including predictor variables not easily quantifiable or defined, low statistical power available to detect events, and no evidence of impact or implementation of these models.(20) Moreover, while identifying ADEs/ADRs is important, these outcomes may be less important to patients, health systems, and payors compared to hospitalizations or ED visits. A review of the literature identified two models for predicting ADR-related hospitalizations among community-dwelling older adults.(17, 18) However, shortcomings of these models include the inclusion of predictors in the model not readily available in the electronic health record (such as functional status and health-related quality of life scales obtained from a clinical trial)(17) and identification of risk factors only among hospitalized community-dwelling patients and not a broader population.(18) Thus, there is a need for a risk prediction model that could be used in the primary care setting for allocation to different intensities of deprescribing interventions which uses outcomes important to patients and payors and employs easily available and updated data. Importantly, measures used in the predictor model should be pragmatic and easily found in administrative data (such as electronic health record data) for reproducibility in other health systems and settings. Moreover, ideally, to facilitate implementation, a practical risk prediction model should incorporate existing pharmacy and healthcare utilization measures that health systems may already be tracking or may use in the future, increasing the likelihood of implementation.
Most risk prediction models have employed traditional statistical methods such as logistic regression to predict the risk of a binary outcome. This approach uses a set of clinical, demographic, and other variables selected based on assumptions and prior literature to predict the outcome. As Goldstein et al. have noted, limitations of these approaches include the potential for a lack of linearity between the risk factors and the outcome, which may not be correctly modeled in a simple risk prediction model; heterogeneity of effects due to interactions; and a limit on the number of prediction variables.(22) However, newer approaches to risk prediction have used machine learning methods.(22) Advantages include the ability to include more predictors, to more easily incorporate non-linearity, and to mitigate missing data without imputation.(22) Limitations include the potential for incorporating and amplifying existing racial biases (see below), the lack of an easily clinically interpretable relationship between the predictors and outcome, issues incorporating temporal data, and challenges creating risk scores that can be meaningfully used in clinical applications when using some machine learning approaches.(22) Machine learning models may also not perform any better than models using traditional statistical methods, highlighting the importance of comparing both approaches.
An important consideration in the use of machine learning models is that they may amplify existing racial, ethnic, gender, and other biases.(23) There are known biases in healthcare access and delivery such as differential treatment of pain,(24) timeliness to radiography and surgery,(25, 26) use of physical restraints in the emergency setting,(27)among many other examples. Race corrections in clinical algorithms, such as the estimate glomular filtration rate (eGFR), have recently been under scrutiny for exacerbating racial and ethnic disparities.(28) Incorporating clinical and healthcare utilization variables into any algorithm – machine learning or otherwise – carries a risk of integrating these existing biases into the algorithm. Thus, integrating a variety of “fairness metrics” can help identify whether different groups are treated equally in the algorithm.(29)
The objective of this paper is to describe the creation, validation, and comparison of two risk prediction modeling approaches for community-dwelling older adults to identify individuals at highest risk for adverse drug event-related hospitalizations. One approach will use traditional statistical methods, the second will use a machine learning approach. We used the Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis (TRIPOD) checklist and the PROBAST (Prediction model Risk Of Bias Assessment Tool), a tool for assessing the risk of bias to guide our methods.(30, 31) If successful, the risk prediction model will be used to guide a deprescribing strategy at the health system level.