Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Public Health


Epidemiology and Biostatistics

First Advisor

Erin L. Abner

Second Advisor

Daniela Moga


According to the United States Census Bureau, 16.8% of the population was 65 years and older in 2021, and it is expected that by 2060 that number will increase to about 30% (about 114 million people). Aging is associated with physiological changes in all systems of the body. These changes impact the pharmacodynamics and pharmacokinetic characteristics of drugs. Furthermore, older adults usually have several chronic conditions, which increases their exposure to medications. Increased vulnerability combined with increasing exposure puts elderly people at higher risk for drug interactions and adverse events.

Charlesworth et al. (2014) found that the prevalence of polypharmacy, most commonly defined as the concomitant use of 5 or more medications, among US elderly increased from 13% in 1988 to 39% in 2010. An analysis of the Atherosclerosis Risk in Communities study population found a polypharmacy prevalence of about 53%, while a South Carolina-based study reported a polypharmacy prevalence of about 30%. Polypharmacy has been associated with medication errors, drug interactions, increased health-service utilization, and adverse drug reactions. Thus, it is clear that polypharmacy may affect a large proportion of older adults, and thus is a important public health issue.

Medication Therapy Management (MTM) is one method of addressing polypharmacy. Medicare developed an MTM program, with four principal aims: 1) medication reconciliation; 2) prevention of adverse events; 3) identification of drug interactions and missing therapies; and 4) improve adherence. Medicare has provided an MTM benefit for Part D enrollees since 2006. Medicare MTM programs are provided by a pharmacist or other qualified professional and include at least quarterly Targeted Medication Reviews (TMRs) and an annual Comprehensive Medication Review (CMR), in which the pharmacist evaluates the medications used by a particular patient, taking into consideration both the drug indications and the individual characteristics of the patient.

While polypharmacy and MTM interventions are rapidly growing areas of pharmacoepidemiological research, many gaps in our understanding remain. Although elderly persons are at especially high risk for polypharmacy and most research about it is focused on elderly populations, younger adults are not immune to the risks of polypharmacy but are not often studied. On the other hand, while MTM has been available to eligible Medicare Part D beneficiaries since 2006, research on its characterization, utilization and relationship to health outcomes (including mortality) is lacking. Taking all the above into consideration, this dissertation research aims to address the above research gaps using two data sources: baseline data from the Maule Cohort, a population-based prospective cohort of adults aged 35-74 residing in Molina, Chile; and Medicare Part D and MTM beneficiary data (2012-2016).

Digital Object Identifier (DOI)

Available for download on Friday, January 03, 2025