Doctors Should Ensure that PD Patients Adhere to Antidepressants, Study Suggests

Poor adherence to antidepressants is correlated with an increase in all-cause mortality in patients with Parkinson’s disease (PD), a new study suggests. Based on the findings, the study’s authors recommend that neurologists, psychiatrists, and primary-care physicians prioritize the use of, and adherence to, antidepressants as indicated.

The study, “Low adherence to antidepressants is associated with increased mortality in Parkinson disease patients,” was published in the journal Parkinsonism and Related Disorders.

One of the most common psychiatric symptoms of PD is depression, which is associated with a decrease in the quality of life and worse clinical outcomes. Studies estimate that 50% of PD patients have symptoms of depression, and approximately 10-20% have major depressive disorder (MDD).

The main treatment for MDD in PD patients is antidepressant medication, which also has been shown to positively affect other PD-associated physical conditions.

Studies have shown that using antidepressants has clear benefits for people with PD, but those benefits are directly linked to whether or not a patient adheres to taking them. For example, MDD patients who have low adherence to antidepressants — in other words, who don’t take them as prescribed — tend to have more emergency room visits, higher hospitalization rates, and greater severity of depression, the study found.

Adherence to antidepressant medication tends to vary for patients with PD and is often low. That is linked to poorer clinical outcomes and higher health-related costs.

Until now, studies had been lacking that evaluated the influence of antidepressant adherence to outcomes in patients with PD, particularly in the context of mortality. Researchers set out to fill in those gaps, hypothesizing that the risk of mortality increases if PD patients have low adherence to antidepressant medication.

From a database of over 4 million people, researchers retrospectively followed 8,553 PD patients who purchased an antidepressant between 2008 and 2011.

Adherence was measured as a ratio between dispensed and prescribed durations. Good adherence meant a ratio higher than 80% (4,219 patients), while moderate adherence was 50-80% (1,584 patients), poor adherence was 20-50% (1,184 patients), and non-adherence was less than 20% (1,566).

Initial study results showed that the unadjusted mortality rates for non-adherent, as well as poor, moderate, and good adherence, were 20.4%, 25.1%, 23.4%, and 25.6%, respectively. However, after adjusting for demographic and clinical variables, the non-adherent group had a significantly higher mortality rate, as did the poor-adherence group. These patients had a 43% and 26% higher risk of death, respectively, compared with the good-adherence group.

Men had a 49% higher risk than women.

Researchers also looked at comorbidities (simultaneously existing conditions) and their correlation to mortality. They found that when patients had three to four comorbidities, their risk of death was 30% greater than those with none to two comorbidities. That risk increased to 78% for patients with five or more comorbidities.

“The present four-year follow-up study is the first to demonstrate the inverse association between adherence to [antidepressants] and all-cause mortality in a general population-based large cohort of patients with PD,” the team stated. “The beneficial effect of adherence to AD may be particularly important in the high-risk population of patients with PD.”

“We suggest that neurologists, psychiatrists, and primary-care physicians prioritize the diligent use and efforts to enhance their patients’ adherence to [antidepressants] when indicated, as it may be associated with increased life-expectancy,” they added.