Effects of Medication Nonadherence and Comorbidity on Health Resource Utilization in Schizophrenia

Medication nonadherence to antipsychotic drugs, which is commonly seen in patients with schizophrenia who have comorbidities, not only affects the quality of life of individuals suffering from the condition, but can also lead to worsening of disease condition, adverse outcomes, excessive use of health care resources, and higher medical costs.

To determine the effect of nonadherence to antipsychotics and related disease comorbidities on medical care utilization with respect to inpatient hospital visits, outpatient visits, office visits, and emergency room (ER) visits.

Retrospective, cross-sectional research data was obtained from the Medical Expenditure Panel Surveys (MEPS) for the years 2010-2014. The proportion of days covered (PDC) adherence measure was used to identify and classify individuals as adherent (PDC ≥ 80%) or nonadherent (PDC < 80%). A logistic regression analysis was used to further examine the effect of key study variables and comorbidity on medication nonadherence in patients with schizophrenia. Using the Student's t-test, population characteristics were statistically compared between the adherent and nonadherent populations and between populations with comorbidities and without comorbidities with respect to inpatient, outpatient, office, and ER visits.

Of 1.2 million people who reported having schizophrenia in MEPS from 2010 to 2014, as many as 71% were found to be nonadherent to antipsychotic medications (PDC < 80%). Results showed that women (OR = 3.594, 95% CI = 1.33-11.40, P = 0.030) and people with less than 15 years of education (OR = 20.85, 95% CI = 3.91-111.09, P = 0.0005) were more likely to be nonadherent to antipsychotic medications than all other demographics. Compared with the adherent schizophrenia population (n = 353,349), the nonadherent population (n = 868,737) had greater utilization of outpatient visits (0.68 vs. 1.92, P < 0.0001) and office visits (10.95 vs. 18.21, P < 0.0001) but had lower utilization of inpatient visits (0.82 vs. 0.45, P < 0.0001) and ER visits (1.03 vs. 0.79, P = 0.1036). Compared with the schizophrenia population without comorbidities, the population with comorbidities (a classification based on a Charlson Comorbidity Index score of ≥ 1) had greater utilization of inpatient (0.39 vs. 0.76, P < 0.0001); office (13.39 vs. 19.34, P < 0.0001); and ER visits (0.39 vs. 1.41, P < 0.0001) but had lower utilization of outpatient visits (1.86 vs. 1.21, P < 0.0001).

Greater medical care resources are used by nonadherent populations with schizophrenia and comorbidities than those without comorbidities. Together, nonadherence and comorbidities pose significant risks to patients with schizophrenia, in clinical and financial terms, and addressing problems stemming from such risks should be an area of priority in schizophrenia management.

No outside funding supported this study. The authors have no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.