Relationship of depression, disability, and quality of life in Parkinson's disease: A hospital-based case-control study
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.79133
Source of Support: None, Conflict of Interest: None
Background : Depression, anxiety, cognitive impairment, sleep disturbances are common neuropsychiatric manifestations in Parkinson's disease (PD). Aims : To compare the prevalence and severity of depression in PD with a group of patients with other chronic medical illnesses and ascertain the relationship of depression with disability and quality of life in PD. Settings and Design : Hospital-based prospective case-control study. Patients and Methods : Forty-six PD patients and 30 non-PD controls having chronic medical conditions were studied. All were assessed by Beck Depression Inventory (BDI) and Montgomery Asberg Depression Rating Scale (MADRS), World Health Organization Disability Assessment Schedule (WHODAS II) and World Health Organization Quality of Life Scale-Brief Version (WHOQOL-Bref). Statistical Analysis Used : SPSS Version 13.0 was used for analysis which included descriptive tests, independent t test, chi-square test, Fisher's exact test, and Pearson's correlation coefficient. Results : The prevalence of depression was higher and more severe in PD than controls (MADRS: 54.3% vs 23.3%, P<0.01; BDI 49.9% vs 23.4%, P<0.05). PD patients had significantly greater overall disability than controls (36.8±19.4 vs 15.1±15.4; P<0.001), and the difference was observed in all six domains of WHODAS II. Conclusions : PD patients had inferior quality of life than controls in all four spheres of WHOQOL-Bref. In PD, depression correlated positively with various domains of disability (P<0.001) and negatively with quality of life (P<0.001). In summary, the prevalence and severity of depression is significantly higher in PD than can be explained by chronic illness. Depression plays an important role in determining the disability and quality of life.
Keywords: Depression, disability, Parkinson′s disease, quality of life
Depression, anxiety, cognitive impairment, sleep disturbances are common neuropsychiatric manifestations in Parkinson's disease (PD). , An association between Parkinsonism More Details and depression has been established in both community , and hospital-based ,, studies. The prevalence of moderate to mild depression in PD is 24.1-45.5% in community-based studies  to 71% in hospital-based studies, especially in women. A recent systematic review indicates that depression or dysthymia is present in 52% of PD patients. 
Depression in PD is not viewed only "reactive" to the increasing disability but also as an integral part of the disease. , A higher prevalence of depression in PD compared to similar chronic, disabling medical illnesses supports this view. , Depression in PD is a risk factor for cognitive impairment , disability , and poor quality of life. , There is paucity of literature in this field from the Indian subcontinent.
The aims of this study were to (i) determine the prevalence of depression in elderly PD patients in comparison to a group of elderly patients with chronic medical conditions, and (ii) ascertain the relationship between depression and the stage, severity, degree of disability, and quality of life.
The study was conducted at the National Institute of Mental Health and Neurosciences (NIMHANS) and St. John's Medical College and Hospital (SJMCH), India. Forty-six consecutive idiopathic PD patients, 50 years and above (mean age: 65.5±9.4 years; mean duration of illness: 4.3±3.5 years), diagnosed according to UKPDS brain bank criteria,  were recruited from Neurology clinics of NIMHANS. The mean age of onset of symptoms was 61.2 years. The control group consisted of age- and sex-matched consecutive patients selected from general Medical clinic of SJMCH with various chronic medical illnesses such as diabetes mellitus, hypertension, bronchial asthma, ischemic heart disease, etc. Patients of either group having history of cerebrovascular disease, head injury, demyelinating illnesses, severe visual or auditory impairment, substance dependence other than nicotine, psychiatric illnesses such as bipolar affective disorder, recurrent depressive disorder, schizophrenia, and other psychosis were excluded. The PD patients as well as the controls were comparable in terms of recruitment region and socioeconomic status and all subjects were from outpatient clinics and did not need hospital admission at the time of interview. All subjects were screened for cognitive dysfunction using the Hindi Adaptation of the Mini Mental Status Examination (HMSE).  Hindi is the local vernacular in India. Any subject of either group scoring <21 (for literates) or <19 (for illiterates) was excluded from the study.
The study was approved by the Institute's Ethics committees at both the centers. Written informed consent was taken from every subject.
Patients with PD were evaluated by sections I-III of the Unified Parkinson's Disease Rating Scale (UPDRS). The staging of disease was done using Hoehn and Yahr Scale.  For all subjects, assessments included (a) depression by Beck Depression Inventory (BDI),  a self-assessment tool and Montgomery Asberg Depression Rating Scale (MADRS),  (b) disability by the World Health Organization Disability Assessment Schedule (WHODAS II),  and (c) quality of life by the World Health Organization Quality of Life Scale - Brief Version (WHOQOL-Bref).  On BDI, a total score of 14-19 was considered mild depression, 20-28 moderate depression, and 29-63 as severe depression. On MADRS, a total score of 14 and above was considered depressed. A 36-item interviewer administered WHODAS II version was used for complete assessment of disability and it provided a profile of functioning across six activity domains, as well as a general disability score. The ratings are made on a scale of 1-5 (1 = absent, 2 = mild, 3 = moderate, 4 = severe, and 5 = extreme). The period of evaluation was over the past 30 days. WHOQOL-Bref Field version was a 26-item self-administered questionnaire, scale which emphasizes the subjective responses of patients rather than their objective life conditions with assessment made over the preceding 2 weeks. It covered four domains which were derived via a polytomous scoring algorithm which was adjusted for relative order of the items and converted onto a 0-100 scale.
SPSS Version 13.0 was used for analysis which included descriptive tests, independent t test, chi-square test, Fisher's exact test, and Pearson's correlation coefficient.
Forty-six patients with PD and 30 controls with various chronic diseases (33.3% diabetes mellitus, 30% hypertension, 10% ischemic heart disease, 6.7% diabetes and hypertension, and 3.3% each of bronchial asthma, hypothyroidism, osteoarthritis, cervical spondylosis, pulmonary tuberculosis, and diabetes with ischemic heart disease) were evaluated in the study. The two groups were comparable for age, gender, education, socioeconomic status, and cognitive functions as measured by HMSE. [Table 1] describes the general characteristics of these two study groups.
The mean duration of illness of PD patients was 4.3±3.5 years. Majority of patients were in H & Y Stage-1 (23.9%) and Stage 2 (32.6%) and the rest belonged to Stages 3 and 4 (21.7% each). The mean total UPDRS score was 47.1±24.7, and the mean component scores were 2.3±2.2 for Part-I, 13.2±7.2 for Part II, and 30.1±16.3 for Part III.
Prevalence and severity of depression
Assessment of depression by both BDI and MADRS indicated that the prevalence of depression was significantly higher in PD compared to controls. The prevalence of depression was 54.3% in PD and 23.3% in controls (P<0.01) on MADRS scale and 49.9% in PD and 23.4% in controls (P<0.05) on the BDI scale. On BDI scale, 41.3% of PD had severe depression and 4.3% each had mild and moderate depression, whereas, in controls, 16.7% had severe depression and 6.7% had moderate depression. The severity of depression in PD was greater than the control group of patients with chronic medical illnesses, evidenced both by BDI (P=0.007) and MADRS scales (P=0.004) [Table 2].
Disability and quality of life
PD patients had a significantly greater overall disability than the controls (36.8±19.4 vs 15.1±15.4; P<0.001). This difference was observed in all the six domains of (WHODAS II) [Table 2]. A lower quality of life was observed in PD compared to controls in all the four spheres, that is, physical health, psychological health, social relationships, and environment [Table 2].
Correlation between disease variables, depression, disability and quality of life in PD
BDI scores had significant positive correlation with the scores of UPDRS-I (r=0.83; P<0.001), UPDRS-II (r=0.47; P=0.001) and UPDRS-III (r=0.44; P=0.002). There was a significant positive correlation between scores for depression as measured by BDI and MADRS and the various domains of disability measured by WHODAS (P<0.001), and negative correlation with the quality of life (P<0.001) [Table 3]. The duration of illness and the scores of UPDRS-I, II, and III correlated positively with the disability scores and negatively with the quality of life scores [Table 4].
Our results indicate that between a comparable group of elderly patients with PD and other chronic diseases, the prevalence of depression was significantly higher in PD (49.9-54.3% vs 23.4%). The higher prevalence of depression in PD in comparison to other chronic diseases is in keeping with earlier research using other tools to assess depression such as Hamilton Depression Rating Scale  and Geriatric Depression Scale.  A community-based study  with methodology similar to ours reported that more patients with PD (50.6%) were clinically depressed than those with diabetes. The present study had a similar prevalence of clinically relevant depressive symptoms in PD, that is, 49.9% on BDI and 54.3% on MADRS.
Depression in PD was significantly more severe than in medically ill group assessed by both scales. In the community-based study mentioned above,  45.5% had mild depression and 5.1% only had moderate to severe depressive symptoms. On the contrary in our hospital-based study, 41.3% of PD had severe depression, while mild and moderate depression were present in 4.3% each. This higher prevalence of severe depression may have resulted from a biased sampling in our hospital which is a tertiary Neurology referral center.
Our study showed that disability (both general and specific domains) was significantly higher in PD than in controls, though majority (78.3%) of PD patients were in mild to moderate stage (H & Y stages 1-3). Moreover, there was some variation in the profile of disability between the two groups: while PD patients had a higher disability across all domains, highest being for life activities, the control group had low disability in self-care and in getting around.
Quality of life of PD, measured by WHOQOL-Bref, was poor when compared to controls in almost all domains. PD patients had poorer scores in physical, psychological, and environmental domains while the score in social domain was slightly better but still less than controls. Using different assessment tools such as Nottingham Health Profile for assessing Health Related Quality of Life and Parkinson's Disease Quality of Life Questionnaire, other studies have also reported poor quality of life in PD when compared to other medical conditions. 
Various disability domain scores in PD correlated negatively with physical, psychological, social, and environmental quality of life, which suggests that disability had significant negative effect on quality of life. Among the various factors which predict poor quality of life in PD, disability is of paramount relevance, , other being depression which is discussed below.
There was a significant positive correlation between the severity of depression in PD and the severity of disability measured by WHODAS II and the UPDRS-III. The correlation remained significant across every domain of disability and depression. In the same sample, there was a significant negative correlation between the severity of depression and quality of life in various spheres, that is, depression had a negative effect on the quality of life in PD. It has been seen in the same group that disability is the other factor which had a negative effect on quality of life (vide supra).
Depression has been reported to be the most important determinant for poor quality of life and disability in PD. ,,,,,,,,, Our study, while confirming this, has also established a significant negative correlation between the disability and quality of life. This finding has major implications, since treating depression in PD can significantly reduce disability and improve quality of life. It is to be emphasized that symptoms of PD and depression often overlap, leading to an underestimation of depression. Early detection of depression is of paramount importance and both medication and counseling therapies have been found to be useful. 
Limitations of our study include small sample size, cross-sectional design, and patient selection bias as our hospital is a tertiary care hospital. Therefore the results may not be generalized to community-based sample of PD patients. Although our study was unique as we compared with a control group who had other chronic illnesses and found a much higher prevalence of depression, disability, and lower quality of life, we were unable to match the duration and severity of the chronic illness in the controls with PD. Further studies are required to determine to what extent improvement of disability and quality of life in PD can be achieved by treating depression, in addition to dopaminergic drugs.
[Table 1], [Table 2], [Table 3], [Table 4]