Mood problems have a greater impact on quality of life among Parkinson’s patients who have had the neurodegenerative disorder for a long time, compared with those who are earlier in their disease course, new findings show.
The results were published in the International Journal of Geriatric Psychiatry, in the study, “Mood in Parkinson’s Disease: From Early to Late‐Stage Disease.“
Mood disorders like depression are common among people with Parkinson’s. Indeed, as many as 60% of patients will experience depression at some point during the disease’s course. It is likely that the biological processes of Parkinson’s itself contribute to the development of depression, researchers say — though stress that comes from living with the disease also likely plays a role.
Although depression is acknowledged as a major problem for individuals with Parkinson’s, little is known about when in the course of the disease such mood problems are most common — or most problematic.
In the new study, the researchers aimed to determine how disease duration is related to the frequency of depression and other mood-related problems in people with Parkinson’s. The team also sought to assess how such disorders impact patients’ quality of life. To this end, the researchers analyzed data from the COPPADIS cohort, an observational study of people with Parkinson’s in Spain.
A variety of assessments were completed by study participants at various disease time points. Of relevance, the patients’ depression symptoms were assessed using the Beck Depression Inventory-II (BDI-II). Health-related quality of life (QoL) was measured with the 39-item Parkinson’s disease Questionnaire (PDQ-39SI), with overall QoL evaluated with the European Health Interview Survey-Quality of Life 8 Item-Index (EUROHIS-QOL8).
In total, data on 663 people with Parkinson’s were analyzed. The patients’ average age was 62.6 years, and 59.6% were male. Based on disease duration, the patients were divided into three groups: Group A comprised 332 people who had a disease duration less than five years; Group B included 221 people with a disease duration between five and 10 years, and Group C included 110 individuals with a disease duration longer than a decade.
There were no significant differences in BDI-II scores between the three groups, nor was there any statistical evidence of a significant association between BDI-II scores and disease duration. About half of participants in each group reported symptoms indicative of depression.
No differences were found among the groups in the various types of depression, as classified based on BDI-II scores.
“The present study of a large population of PD [Parkinson’s disease] patients observes that depression is frequent in PD and suggests that the frequency of different types of depression (major vs minor vs subthreshold) does not change over time,” the researchers wrote.
Using statistical models, the investigators calculated the extent to which the two health-related quality of life measurements could be explained by other analyzed factors, including BDI-II scores. For both PDQ-39SI and EUROHIS-QOL8, BDI-II scores were a significant influencing factor — which mathematically suggests that depression has a substantial effect on quality of life.
Interestingly, the percentage of health-related quality of life variance explained by BDI-II scores was substantially higher in Group C than for the other two groups: 23.7% (Group C) vs. 8.5% (Group A) and 6.5% (Group B) for PDQ-39SI, and 26.93% (Group C) vs. 12.46% (Group A) and 12.89% (group B) for EUROHIS-QOL8.
“We observed that the magnitude of the effect of mood on QoL seems to be greater for patients with long disease duration. … In other words, in PD, depression could be no more frequent in the long-term but its effect could be more disabling,” the researchers concluded.
The team suggested that this might be because, after years of living with a chronic disease, mood has a greater effect on daily life and patients’ expectations are lower.
“From a practical point of view,” they added, “in the evaluation of all patients with PD, it is always necessary to ask about depressive symptoms since depression is frequent regardless of the evolutionary moment of the disease and to pay special attention to the fact that in patients with a longer disease duration the impact of depression on their perception of QoL may be greater.”
This implies that providing treatments targeted at easing depressive symptoms might be of particular benefit, in terms of health-related quality of life, for people with longer disease duration.
Further research is needed to validate these results, the investigators said. In particular, they stressed the need for long-term observational studies following the same patients over time — as opposed to a cross-sectional study such as this one, which assessed different people with varying disease durations.
The investigators also said that the inclusion criteria of the analyzed cohort, such as excluding people with dementia, mean that the results might not be applicable to all people with Parkinson’s.
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