Research report
The community prevalence of depression in older Australians

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Abstract

Objective

To estimate the prevalence of depression among older adults in Australia.

Method

All general practitioners in Australia's five most populous states who satisfied certain eligibility criteria (e.g., sufficient weekly working hours, sufficient numbers of elderly patients) were invited to participate. Those who consented were asked to identify all of their patients aged 60+ and invite them (either directly or via the study team) to complete a questionnaire. The questionnaire identified those who had experienced ‘clinically significant depression’ and those who had experienced a ‘major depressive episode’ in the past two weeks, via the Patient Health Questionnaire (PHQ-9). Consenting patients completed the questionnaire and returned it to the study team in a reply-paid envelope.

Results

In total, 22,251 patients returned questionnaires. Overall, the age-adjusted rate of clinically significant depression was 8.2% (95%CI = 7.8%–8.6%), with the age-adjusted rates for males being 8.6% (95%CI = 7.9%–9.2%) and for females being 7.9% (95%CI = 7.4%–8.4%). The overall, male and female age-adjusted rates for a major depressive episode were 1.8% (95%CI = 1.6%–2.0%), 1.9% (95%CI = 1.6%–2.2%) and 1.7% (95%CI = 1.5%–2.0%), respectively.

Discussion

Our study suggests that depression among older people is a major public health problem. The above estimates provide guidance for efficient planning of services, and establish a baseline against which preventive and treatment interventions can be assessed. Armed with this information, we can progress efforts at reducing this major health problem and its consequences.

Introduction

Depression among older people is a significant public health issue. The impact of depression on older people is considerable because their social and family networks may be limited and their coping strategies suboptimal (Lawrence et al., 2006). Older adults with depression may also be reluctant to seek help for various reasons, including a lack of understanding of what depression is (Lawrence et al., 2006), stigma and shame (Penter and Other-Gee, 2005), and a generational stoicism (Penter and Other-Gee, 2005). Of concern for this age group, depression can also exacerbate physical morbidity (Braam et al., 2005), reduce quality of life (Blazer, 2003), and increase the risk of death (Adamson et al., 2005), including death by suicide (Grek, 2007).

The exact magnitude of the burden caused by depression in older people is unknown. In a recent review of 122 papers in this area, Djernes (2006) found that the reported prevalence of depression ranged from 1% to 49%. The Australian studies that were included in the review reported prevalence rates from 1% to 44% (Brodaty et al., 2003, Henderson et al., 1993, Snowdon et al., 1996, Snowdon and Lane, 1995, Wilhelm et al., 2003). This wide divergence can be attributed largely to methodological factors. Firstly, the definition of depression used in the identified studies was highly variable, and this is likely to have had an impact on prevalence estimates. Not surprisingly, surveys that considered major, moderate or severe depression yielded lower prevalence rates than those investigating dysthymia or minor depression. Even when the same degree of severity was considered, however, surveys that used validated diagnostic criteria (e.g., DSM-IV-TR (American Psychiatric Association, 2000) or ICD-10 (World Health Organization, 2005)) tended to yield lower prevalence estimates than those which assessed depression using other criteria (e.g., the GMS-AGECAT (Copeland et al., 1986)), or measured depressive symptoms using depression scales (Djernes, 2006).

Secondly, the sampling strategies used by the different prevalence studies may have contributed to the heterogeneity of findings in Djernes (2006) review. Studies in which older people were sampled from private households tended to yield lower estimates than studies in which the sample was drawn from institutions (e.g., aged residential care facilities).

Thirdly, varying sample sizes may have influenced the robustness of given prevalence estimates. Some studies included in Djernes (2006) review had sample sizes of several thousand, whereas others relied on data from fewer than 100 participants. The studies with smaller sample sizes may have produced less reliable estimates and arguably introduced outliers into the range reported by Djernes.

Various experts in the field have tried to address the above issues in different ways. A systematic review by Beekman et al. (1999), for example, combined prevalence estimates from 34 studies, weighting them by sample size. By doing this, they found weighted average prevalence estimates of 1.8% for major depression, 9.8% for minor depression, and 13.5% for all depressive syndromes. They acknowledged, however, that their analytic method did not take into account methodological differences between studies (e.g., different instruments), which led them and others to form a consortium known as the EURODEP Concerted Action Programme (Braam et al., 2005, Copeland et al., 2004, Copeland et al., 1999). EURODEP has attempted to combine data from 14 research groups in 11 European countries by ‘cross-walking’ a number of different instruments to a single ‘harmonised depressive symptom scale’. By doing this, EURODEP has reported an overall prevalence of depression of 12.3% in a combined sample of 22,570 adults aged 65 and over.

We took a different approach to measuring the prevalence of depression among older adults, and offer our findings for comparison with other Australian estimates in an effort to inform service planning in this area. We conducted a large-scale study of the community prevalence of depression in older people, using a single instrument to assess a ‘major depressive episode’ and ‘clinically significant depression’. We accessed our sample via general practice, on the grounds that 90% of older adults visit (or are visited by) their general practitioner at least once per year (Bayram et al., 2003). We felt that identifying a substantial, representative group of general practitioners, and in turn asking them to identify all of their older patients, had the potential to yield a large sample from which robust findings could be generalised.

This prevalence study is part of a larger investigation, known as the DEPS-GP project, which is a cluster randomised controlled trial examining the efficacy of an educational intervention in increasing general practitioners' awareness of and ability to identify and manage depression and suicidality in later life. The DEPS-GP project is being conducted by investigators from nine Australian and New Zealand universities, and has ethics approval from the human research ethics committees of each of these and the Royal Australian College of General Practitioners. This prevalence study represents cross-sectional data from the baseline phase of the DEPS-GP project (September to December 2005).

Section snippets

Recruitment of sample

A two-stage recruitment strategy was used which involved initial recruitment of general practitioners and subsequent recruitment of their patients. Details of this recruitment strategy have been described in detail elsewhere (Williamson et al., 2007), and are briefly summarised below.

General practitioners in Australia's five most populous states (New South Wales, Victoria, Queensland, Western Australia and South Australia) were identified via a list held by the Australasian Medical Publishing

Profile of sample

Table 1 provides an age/sex breakdown of the sample and offers comparisons to the general population of older Australians, using data from the 2006 Census. In general terms, our sample was reasonably representative of the general population, although there was a slight under-representation by those in the youngest of the three age groups (60–69 years) and a slight over-representation by those in the middle age group (70–79 years), particularly for males.

Prevalence of depression

Overall, the age-adjusted rate of

Summary of key findings

Our study suggests that, at any given point in time, around 8% of older Australians are experiencing clinically significant depressive symptoms that are likely to disrupt their daily lives. Nearly 2% may be experiencing a major depressive episode.

Comparison with other prevalence estimates

It is worth considering how these 2005 figures compare with other Australian estimates, some of which are now quite old. Our figures are, not surprisingly, considerably lower than those reported in an earlier study of depression among nursing home

Conclusions

With 8% of older adults experiencing clinically significant depressive symptoms, depression among older people is clearly a major public health problem. The estimates provided in our study provide guidance for efficient planning of services, and establish a baseline against which preventive and treatment interventions can be assessed. Armed with this information, we can progress efforts at reducing this major health problem and its consequences.

Role of funding source

Funding for the DEPS-GP project was provided by the National Health and Medical Research Council and beyondblue. These funding bodies had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication.

Conflict of interest

The authors have no conflicts of interest to declare.

Acknowledgements

The authors would like to acknowledge the study's funders, the National Health and Medical Research Council and beyondblue. They would also like to acknowledge the contribution of other DEPS-GP investigators: Gerard Byrne, Leon Flicker, Ngaire Kerse and Ian Wilson. They are also grateful to DEPS-GP research staff for their assistance: Peter Clissa, Jane Dodding, Skye Murray and Carmen Tang. They would also like to thank all participating GPs and patients for giving up their time to take part in

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