Prevalence of depression in type 2 diabetes patients in German primary care practices
Introduction
Diabetes and depression are highly prevalent in Europe. There are about 60 million adults with diabetes in this region of the world (10.3% of men and 9.6% of women) and prevalence of the chronic condition is increasing across all age groups, in parallel to an increase in overweight and obesity, unhealthy diet and physical inactivity (WHO, 2015a). Millions of European people, the majority of them women, suffer from serious depression during their lives and 50% of these cases remain untreated (WHO, 2015a, WHO, 2015b). As diabetes and depression are common disorders in Europe and as the associated costs for European countries already exceed millions of euros, the relationship between the two warrants careful examination.
A number of works have already shown an association between diabetes and depression (Snoek, Bremmer, & Hermanns, 2015). In 2001, Anderson, Freedland, Clouse, and Lustman (2001) analysed 42 studies aimed at the estimation of depression prevalence in people with type 1 and type 2 diabetes. They showed that the presence of diabetes doubled the odds of comorbid depression and their finding was later confirmed by other studies on the topic (Roy & Lloyd, 2012). They also demonstrated that the prevalence of depression was even higher in people with diabetes when the chronic condition was reported by the patient him/herself rather than by clinicians (Snoek et al., 2015). More recently, another meta-analysis indicated a significant link between treatment non-adherence in diabetes and depression (Gonzalez et al., 2008), underlining the tenuous link between the mental disorder and treatments regulating glycaemia, at least in cases of type 2 diabetes (Zhang et al., 2015). Finally, the association between the two disorders is not unidirectional; depression is also known to predispose individuals to diabetes (Pan et al., 2010), and the association is therefore considered bidirectional.
Despite these works, the relationship between depression and diabetes is still poorly understood (Snoek et al., 2015), with no real consensus as to whether it is causal or merely coincidental. Although depression usually appears before the ages of 25–30, type 1 diabetes and type 2 diabetes often arise in childhood and later in life respectively. Therefore, risk factors related to depression may not be the same for both forms of diabetes. Although depression is more prevalent in people with diabetes, it was recently shown that patients newly diagnosed with type 2 diabetes do not display an increased risk of developing depression (Skinner et al., 2010). Another interesting result is that patients exhibit low levels of distress and anxiety during the first years of the chronic condition (Thoolen, de Ridder, Bensing, Gorter, & Rutten, 2006), suggesting that early and intensive treatments can influence the occurrence of depression. Intriguingly, people with diabetes also reported high distress upon diagnosis (85.2% of patients felt shocked, guilty, angry, anxious, depressed, or helpless) (Peyrot et al., 2005). Finally, several authors have shown that complications related to diabetes are additional risk factors for depression (Badawi et al., 2013, Pouwer et al., 2003). The goal of the present study was to analyse depression in German patients with type 2 diabetes, in the presence or absence of diabetes complications.
Section snippets
Database
The Disease Analyzer database (IMS HEALTH) compiles drug prescriptions, diagnoses, basic medical and demographic data obtained directly and in anonymous format from computer systems used in the practices of general practitioners (Becher, Kostev, & Schröder-Bernhardi, 2009). Diagnoses (ICD-10), prescriptions (Anatomical Therapeutic Chemical (ATC) Classification System) and the quality of reported data have been monitored by IMS based on a number of criteria (e.g. completeness of documentation,
Patient characteristics
A total of 90,412 primary care patients were diagnosed with diabetes in German practices between January 2004 and December 2013. The clinical characteristics of these patients are shown in Table 1. As expected, the mean age was 65.5 years and most of these older patients had diabetes complications or co-diagnoses, most commonly hypertension, lipid metabolism and coronary heart disease (79.7%, 56.0% and 28.8% respectively). 19.7% of them also had high levels of Hb1Ac, indicating poor glycaemic
Discussion
In our study, depression was more common in women and in individuals without private health insurance. Prevalence also increased with the number of diabetes complications. Five of them were associated with a higher risk of depression development: retinopathy, neuropathy, nephropathy, coronary heart disease and stroke. Furthermore, high levels of HbA1c had an important impact on depression, in particular when they were higher than 9, as they were associated with an HR of 2.17. HbA1c thus had the
Acknowledgements
Professional English language editing services were provided by Claudia Jones, MA, Radford, Virginia, United States.
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Conflict of interest: None.