Medication Adherence Didn’t Affect Patients’ Life Quality in Small Study

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by Steve Bryson, PhD |

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People with Parkinson’s disease who failed to take their medication as prescribed — meaning, were nonadherent — showed no difference in measures of health-related quality of life (HRQoL) than those who were fully adherent, a questionnaire study of a patient group found.

This finding surprised its researchers, who noted “that in other disorders (e.g., hypertension, epilepsy, and heart failure), adherence to pharmacological treatment is commonly associated with better HRQoL.”

They speculated this lack of connection may be “a special phenomenon in PD [Parkinson’s disease], which is defined by distinct motor and non-motor symptoms that strongly influence QoL [quality of life].” Patients nonadherent to any degree were mainly male, had greater cognitive impairment and non-motor symptoms, evidence of depression, and took more medications daily.

The study, “Self-Reported Nonadherence to Medication Is Not Associated with Health-Related Quality of Life in Parkinson’s Disease,” was published in the journal Brain Sciences

Nonadherence is a growing issue in the treatment of people with Parkinson’s. Many factors influence nonadherence, including financial and health system barriers, disease-related circumstances, and those specific to a patient, from intentional choice to an inability to follow treatment recommendations.

Studies examining an association between nonadherence and quality of life have been mixed, and most excluded those with cognitive difficulties, a progressive feature of this disorder but a choice in studies that can limit the usefulness of their results.

Researchers at the Jena University Hospital in Germany designed a study of whether self-reported nonadherence related to health-related QoL. In this study, adherence referred to all medications; it was not restricted to Parkinson’s treatments for motor problems or non-motor symptoms.

The analysis included 164 people with Parkinson’s disease, mostly men (100 people or 61%) with a mean age of 71. Their mean disease duration was 9.41 years, and their mean number of daily medications was 7.27. Most were married, 75.6%, and had middle or upper levels of education (77.8%). 

While none of these people had Parkinson’s-related dementia, their mean Montreal cognitive assessment (MoCA) score was 22.46, indicating mild cognitive impairment overall. Several participants scored below 21, due to problems with eyes and fine motor skills. 

Adherence was measured by the self-reported German Stendal Adherence to Medication Score (SAMS), which included 18 questions generating a score from 0 to 72, in which 0 indicated complete adherence (always take medicine), and 72 complete nonadherence (never take medicine). 

For HRQoL, the PDQ-39 questionnaire was used, which has 39 items grouped in eight domains: mobility, daily living activities, communication, emotional well-being, social support, stigma, cognition, and physical discomfort, as well as an overall HRQoL summary index score. Scores for each item range from 0 (never) to 4 (always), with total higher scores representing worse HRQoL.

The team also measured symptoms using the Beck Depression Inventory (BDI), the Movement Disorder Society revision of the Unified Parkinson’s disease rating scale (MDS-UPDRS III) to assess motor abilities, and the non-motor symptoms questionnaire (NMS-Quest).

Results found a mean total SAMS score of 6.7 points: 17 patients (10.4%) were fully adherent (SAMS score = 0), 109 were moderately nonadherent (SAMS scores ranging from 1 to 10.9), and 38 (23.2%) reported clinically meaningful nonadherence (SAMS scores of = 11 or greater). 

Nonadherence was found in analyses to be significantly associated with male gender, lower MoCA score (cognitive impairment), higher NMS-Quest (worse non-motor symptoms) and higher BDI (depression) scores, and a greater number of daily medications.

Initial calculations found SAMS correlated weakly with the cognition PDQ-39 domain, but not with other domains or with the overall score. Fully adherent, moderately nonadherent, and nonadherent patients differed only in regard to cognition.

However, after adjusting for clinical variables, the association between SAMS and HRQoL cognition was no longer statistically significant. 

Further assessment showed a statistically significant difference between patients with different adherence degrees (fully adherent, moderately nonadherent, nonadherent) in the HRQoL cognition domain but not with other PDQ-39 domains. In this domain, there was a significant difference between the fully adherent and nonadherent group, and between the moderately nonadherent and the nonadherent group, but not between the fully adherent and the moderately nonadherent group.

Finally, to examine whether other medical variables could account for these results, variables related to HRQoL, such as depression (BDI measures), cognitive skills (MoCA), and non-motor symptoms (NMS-Quest), were included in the statistical model. Here, BDI and NMS-Quest were significantly associated with the PDQ-39 cognition domain, but not the MoCA score and degree of treatment adherence.

“Our study showed that self-reported nonadherence was not associated with the PDQ-39 summary index, nor with the different domains of the PDQ-39,” the researchers concluded. “The observed predictors of the PDQ-39 in our study, namely motor function, age, depression, and gender, are in line with earlier reports of people” with Parkinson’s disease.

They concluded “that for patients with PD, other aspects are more relevant to HRQoL than [medication] adherence.”

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