Chronic co-morbidities associated with depression in elderly

Background: Depression is a common mental health problem in the elderly population of the world. Objective: To study the chronic co-morbid conditions associated with depression in elderly population. Materials and Methods: A systematic review was conducted on 74 community-based mental health surveys on depression in elderly which were conducted in continents of Asia, Europe, Australia, North America, and South America. All the studies were conducted between 1955 and 2005. The researchers had included only community-based cross-sectional surveys and some prospective studies that had not excluded depression on baseline. These studies were conducted on homogenous community of elderly population in the world, who were selected by simple random sampling technique. A qualitative analysis on 11 of these articles was conducted to study the chronic co-morbidities associated with depression in elderly. Results and Conclusion: The univariate analysis results from 11 studies on various chronic co-morbid conditions associated with depression in elderly revealed that depression in elderly was significantly associated with arthritis, cognitive impairment, visual impairment, functional impairment, and restricted activities of daily living (ADL). The prevalence of depression followed an increasing trend as the number of chronic co-morbidities increased.

Keywords: Chronic, co-morbid, depression, elderly, impairment

The correlates of depression in old age are reported by the World Health Organization as: genetic susceptibility, chronic disease and disability, pain, frustration with limitations in activities of daily living, personality trait (dependent, anxious or avoidant), adverse life events (widowhood, separation, divorce, bereavement, poverty, social isolation), and lack of adequate social support. ^{[1],[2],[3],[4],[5]}

Study Design: A retrospective study based on a systematic review on the prevalence of depression in elderly population.

Setting: Community-based mental health surveys on depression in elderly, conducted in the continents of Asia, Europe, Australia, North America, and South America, were included in this analysis.

Study Period: All the studies that were conducted and published in indexed journals between 1955 and 2005 (i.e., within the last 51 years) constituted the sample.

Sample Size: All published articles on the prevalence of depression in elderly population that were available, adequately analyzed and accessible from the internet, the Central Library of Kasturba Medical College Manipal in Karnataka and the Central Library of Sikkim-Manipal Institute of Medical Sciences (SMIMS) in Sikkim, constituted the study universe.

Databases: The search engines that were utilized for electronic data from the internet were MEDLINE, PUBMED, GOOGLE, YAHOO, EMBASE, PsycINFO and the Cochrane Collaboration Database for original human research articles in the English literature published through 1 January 1955 and 31 December 2005 using the two sets of search items: “Prevalence of Depression in Elderly” and “Prevalence of Elderly Depression.”

Sampling Procedures: Only studies that either covered the total population of the study area or the applied simple random sampling method to identify the study subjects in their corresponding research projects were included for this final systematic review.

Inclusion Criteria: To avoid undesired bias due to design effects from various epidemiological study designs, the researchers had included only community-based cross-sectional surveys on the prevalence of depression and some prospective study designs that had not excluded depression on baseline. All these studies were conducted on homogeneous community of elderly population in the world, who were either selected by a simple random sampling technique or covered under the whole population of the study area. For determining the various chronic co-morbidities associated with depression in elderly, only those articles were included that had at studied at least one co-morbidity associated with depression.

Exclusion Criteria: All the unpublished reports and unavailable or unanalyzed or inaccessible articles from the internet as well as the Central Library of Kasturba Medical College Manipal in Karnataka and Central Library of Sikkim-Manipal Institute of Medical Sciences (SMIMS), Sikkim, on studies regarding the prevalence of depression in an elderly population were excluded from this study. Studies conducted on migrant populations, old age homes, and health care institutions were also excluded from this systematic review in order to avoid biasness. A high prevalence rate of depression was very common among isolated groups of individuals in the community, who had migrated to some other place either due to political force or to meet their physiological or financial needs.

Selection of Articles: In the first step, while searching through all the selected databases, the key words “depression,” “co-morbidity,” “prevalence,” “risk factor,” “elderly,” “aged,” and the text word “community” were used. In the second step, after applying the inclusion and exclusion criteria, all relevant articles (judged on the basis of the title and abstract) were retrieved for more detailed evaluation. In the third step, the bibliographies of relevant articles were searched for additional references. Finally, all retrieved articles were screened to determine which met the following six inclusion criteria: (1) original research published in English, (2) study group of community residents, (3) subjects age 60 years or older, (4) cross-sectional study design that included both old and new cases of depressed elderly individuals in the community, (5) prospective or follow-up studies that have not excluded the depressed elderly individuals at the baseline and (6) acceptable definition of depression (either recognized diagnostic criteria or cut-off on a depression rating scale).

Articles included in this Systematic Review

The following 11 articles are included in the qualitative analysis for studying the chronic co-morbid conditions associated with depression in elderly: Penninx Brenda et al (New Heaven, 1982-88), Geerlings et al (Amsterdam, 1990-96), Liu et al (China, 1993), Pahkala et al (Finland, 1994), Roberts et al (USA, 1995), Chong et al (Taiwan, 1996-1998), Braune et al (Germany, 1997-1998), Newman et al (Canada, 1998), Barua et al (India, 2002), Ostbye et al (Canada, 2005), Chen et al (China, 2005).

Study Instruments: Clinical Diagnoses by Psychiatrists were based on DSM-III-R, DSM IV and ICD-10 criteria. Other standardized study instruments used were Elderly Mental State Examination (GMS), AGECAT, Composite International Diagnostic Inventory (CIDI-SF), CES-D, BDI, HDS, Yesavage Elderly Depression Scale, Centre for Epidemiologic Studies Depression Scale, Mini Mental Status Examination (MMSE), Hamilton Depression Scale (HDS/HAMD), Clinical Rating Scale for Depression, Mini Mental Status Examination and Elderly Depression Screening Scale and Mastering Depression In Primary Care Version 1998.

Assessment of Validity: The validity of each of these study instruments was verified with its individual validity and reliability reports and reconfirmed with the renowned psychiatrists. Some of the studies used the clinical assessment by the individual psychiatrists and the diagnostic criteria were never mentioned. In these cases, the impact factor of the journal where the research article got published was taken into consideration for assessing the quality and standard of research.

Data Collection Procedure

The investigators were trained by the renowned psychiatrists of Kasturba Medical College Manipal, Karnataka, and Sikkim-Manipal Institute of Medical Sciences (SMIMS) on how to interpret the results from different community-based psychiatric evaluation studies. At the beginning, a pilot study was conducted with randomly chosen data from 10 original research articles that surveyed elderly individuals in the age group of 60 years and above, residing in various parts of the world. After applying the inclusion and exclusion criteria, some of these studies used in the pilot study were included for statistical analysis in the final research project.

Abstraction of Data

Information about the size of the study group, subjects’ age, sampling method, criteria for depression, exclusion criteria at baseline, length of study period, number of prevalent cases of depression, risk factors and chronic co-morbid conditions were abstracted from each report.

Data Synthesis

Qualitative: All abstracted information was tabulated. A qualitative systematic review was conducted by summarizing, comparing and contrasting the abstracted data. Since all these studies were cross-sectional in nature, there was not much scope to conduct a detailed analysis of individual risk factors of depression in elderly. So, only the significant risk factors of respective studies were projected in the final report to provide the researchers some clues of the factors that were most frequently found associated with depression in elderly. But their combined strength of association could not be measured, due to the absence of an analytical study design with matched controls, which was a limitation for this research.

Data Analysis: A qualitative analysis was conducted to study the various chronic co-morbid conditions associated with depression in elderly.

A retrospective study based on a systematic review on the prevalence of depression in elderly population was conducted by the investigators where 74 community-based mental health surveys on depression in elderly were analyzed for determining the median prevalence rates and trend of depression in elderly. All the studies, which were included for final analysis, were conducted during the year 1955 to 2005 in the continents of Asia, Europe, Australia, North and South America.

Selection of Articles

The search strategy yielded 896 potentially relevant studies; among these 143 were retrieved for more detailed evaluation. Although 77 studies met the inclusion criteria, we could retrieve main article or structured abstract for only 74 studies which were included for the final analysis. Among these, 69(93.2%) had cross-sectional study design and 5(6.8%) had prospective study design that had not excluded depression on baseline.

Report from the selected 74 articles was used for estimation of the median prevalence of depression in elderly; only 24 studies were shortlisted for analysis of correlates of depression in elderly as they had studied at least one risk factor in detail. Similarly, 11 studies were shortlisted for analysis of chronic co-morbid conditions associated with depression in elderly as they had studied at least one co-morbidity in detail. All other studies were excluded for the following reasons: many did not meet the age criterion, many did not provide detailed information on criteria for confirmation of diagnosis and standard case-definition, many were institution based studies or conducted on migrant population, some study designs were not cross-sectional, some had inadequate sample size or faulty sampling technique, some were prospective studies that had excluded depression at baseline, and some did not meet two or more of the inclusion criteria.

Assessment of Correlates of Depression in Elderly:

A Qualitative Analysis

Twenty different risk factors were studied by univariate analysis in 24 selected articles. Among these, 14 in three or more positive studies and 6 in two positive studies each. Cognitive impairment, restricted Activities of Daily Living (ADL) and chronic co-morbidities like vision or hearing or functional impairment were identified as risk factors for depression in at least two studies each.

[Table 1] shows univariate analysis from 11 studies on various chronic co-morbid conditions associated with depression in elderly. Here, more frequent and strong association of depression in elderly was observed with arthritis, cognitive impairment, visual impairment, functional impairment, and restricted activities of daily living (ADL). However, less frequent significant association was found with diabetes, hypertension, cardiac disorders, bronchial asthma/COPD, cerebro-vascular accidents (CVA), and hearing impairment. A majority of these findings were consistent with the observations by Penninx Brenda et al^[6] [(1982-1988), Iowa, East Boston, New Haven] and Barua et al^[7] (2002, India).

The prevalence of depression often followed an increasing trend as the number of co-morbid chronic conditions increased and this trend was also found to be statistically significant in the studies conducted by Kennedy Gary et al^[5] [(1984-1985), USA] and Barua et al^[7] (2002, India), where the prevalence of depression was highest among those with four or more co-morbid chronic conditions and this difference as compared with other groups was found to be statistically significant.

Since there was heterogeneity in the results for some chronic co-morbid conditions (i.e., functional impairment, cognitive impairment, and chronic co-morbidities), perhaps related to different definitions of these variables in different studies and small study groups in some studies; consequently, the results of the systematic review for these chronic co-morbid conditions must be interpreted cautiously. ^[8]

It was observed that a large proportion of depression among elderly people in the community was attributed to one of the chronic co-morbid conditions. Since, these chronic co-morbid conditions are frequent in elderly age group; their modification could be expected to have an important public health impact. Elderly populations could be screened to identify individuals at high risk of depression. Subsequently, these individuals could be targeted for interventions to abate these potentially chronic co-morbid conditions and reduce the risk of depression. Such interventions might include education about the significance of the chronic co-morbid conditions, bereavement counseling and support, new skills training, “maintenance of routines” protocols, enhancement of social supports, individual or group therapy to facilitate adjustment to loss of function, and sleep enhancement protocols. ^[8]

Source of Support: None, Conflict of Interest: None

[Table 1]