Screening instruments for a population of older adults: The 10-item Kessler Psychological Distress Scale (K10) and the 7-item Generalized Anxiety Disorder Scale (GAD-7)

Highlights

• Cutoff scores of 19 and 23 were found for K10 when screening for minor or major depression in older adults.

• Cutoff scores of 5 were found for GAD-7 when screening for an anxiety disorder in older adults.

• K10 and GAD-7 are useful in discriminating between cases and non-cases of depression and anxiety.

ABSTRACT

Screening tools that appropriately detect older adults׳ mental disorders are of great public health importance. The present study aimed to establish cutoff scores for the 10-item Kessler Psychological Distress (K10) and the 7-item Generalized Anxiety Disorder (GAD-7) scales when screening for depression and anxiety. We used data from participants (n=1811) in the Enquête sur la Santé des Aînés-Service study. Depression and anxiety were measured using DSM-V and DSM-IV criteria. Receiver operating characteristic (ROC) curve analysis provided an area under the curve (AUC) of 0.767 and 0.833 for minor and for major depression when using K10. A cutoff of 19 was found to balance sensitivity (0.794) and specificity (0.664) for minor depression, whereas a cutoff of 23 was found to balance sensitivity (0.692) and specificity (0.811) for major depression. When screening for an anxiety with GAD-7, ROC analysis yielded an AUC of 0.695; a cutoff of 5 was found to balance sensitivity (0.709) and specificity (0.568). No significant differences were found between subgroups of age and gender. Both K10 and GAD-7 were able to discriminate between cases and non-cases when screening for depression and anxiety in an older adult population of primary care service users.

Introduction

Worldwide, the population of older adults, aged 65 and over, is expected to triple by 2050 (WHO, 2011). This increase in population comes along with an increased need for research and advancements in improved mental health for seniors considering the negative impact of mental health issues on quality of life, functionality, cognition as well as physical health, the latter presenting a suggested bidirectional effect with common mental health problems, such as depression and anxiety (Ramasubbu et al., 2012, Roy-Byrne et al., 2008, Rugulies, 2002, Skoog et al., 1993).

Large population based studies in developed countries have reported rates of depression and anxiety ranging from 2.6% to 27% in older adults (Blazer et al., 1987, Scott et al., 2008, Mosier et al., 2010, Kessler et al., 2010). In Canada, a study using the Enquête sur la Santé des Aînés (ESA) survey on the health of older adults showed that 13% and 5.7% of community dwelling seniors reported psychological distress symptoms and filled DSM-IV criteria for depression in the past year (Préville et al., 2008). Using the same data, Grenier et al. (2011) showed that the past year prevalence rate of any anxiety disorder was 5.6% for seniors when using DSM-IV criteria.

Canada has a public managed health care system and all residents have access to primary care. Reports have shown that among the 13% of older adults that suffer from a common mental disorder, fewer than 50% actually receive any treatment (Préville et al., 2008). From a public health perspective, the impact of untreated depression and anxiety is great not only on the individual׳s physical health but also on the health care system. One recent study showed that, in 2010, the excess annual adjusted health care costs of depression, anxiety and co-morbid depression and anxiety reached $27.4, $80.0 and $119.8 million per 1 million in a population of elderly (Vasiliadis et al., 2013).

Given the aging of the population and the important burden of depression and anxiety on the health care system, as well as on individuals, it is important to effectively detect these disorders in both epidemiological and clinical settings. One way to do so is with screening tools that preferably should be simple and short as opposed to extensive questionnaires given the cognitive decline with older age (O’Brien and Grayson, 2013). Moreover it has been reported that the elderly have a harder time accurately completing long questionnaires (O’Connor and Parslow, 2010).

Some screening methods presently in use include the Hospital Anxiety and Depression Scale (HADS) which has been validated in French for the population of Quebec, however, the scale׳s strength in detecting mental disorders is weak (Roberge et al., 2013). Other measures include the 10-item Kessler Psychological Distress Scale (K10) and the 7-item General Anxiety Disorder Scale (GAD-7) (Kessler et al., 2002, Spitzer et al., 2006).

The K10 is a non-specific and concise screening method for psychological distress. There has been a satisfactory evidence of this scale correlating with the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) when looking at anxiety and depression disorders (Andersen et al., 2011, Anderson et al., 2013, Andrews and Slade, 2001, Fassaert et al., 2009, Furukawa et al., 2003, Furukawa et al., 2008). The majority of these validation studies on the K10 have been done on adult populations. Recently, Anderson et al. (2013) highlighted that these validation studies may not be directly applicable to different older adult populations. Their study focused on an older adult population in Australia and found a significant correspondence between K10 scores and the presence of psychological disorders.

The GAD-7 is also a concise scale with only 7 items aimed at screening for anxiety disorders. Its validity and reliability have been tested in both clinical and general population settings. In both settings it has been shown to be a valid and effective measure of anxiety (Spitzer et al., 2006, Kroenke et al., 2007, Löwe et al., 2008). A study by Wild et al. (2014) validated the GAD-7 screening tool on a population of older individuals in Germany and it was considered effective in this population.

The objective of this study was to determine, in a large sample of community living older adults attending primary care health clinics in Quebec, the cutoff for depression and anxiety disorder when using a French adaptation of the K10 and GAD-7 as a screening tool.