Levels of personality functioning and not depression predict decline of plasma glucose concentration in patients with type 2 diabetes mellitus
Introduction
Diabetes mellitus is a common, chronic, and impairing disease that affects about 9% of men and 7.9% of women worldwide [1]. With increasing incidence rates and lower age of onset, it has been called an epidemic by some researchers. About 90% of the individuals suffering from diabetes are diagnosed with type 2 diabetes mellitus. Although there is no known cure to type 2 diabetes, some of its risk factors, symptoms and subsequent long-term damage can be managed through life-style changes or compliance to an evidence-based treatment [2]. Because of the chronicity of type 2 diabetes, adherence to life-style changes or medication have to be maintained life-long. This adherence depends on the subjects’ emotional and cognitive abilities, which are influenced by the patients’ personality and might be impaired due to mental disorders. As in other chronic diseases, the prevalence for mental disorders is higher in individuals with diabetes than in the general population [3]. This is also true for depression and type 2 diabetes [4], [5]. Individuals with type 2 diabetes [6] have higher levels of depressive symptoms, which might be similar to diabetes-specific distress [7]. The direction of the association is likely to be bi-directional: The burden of a diagnosis of and coping with type 2 diabetes can increase the risk of developing a sub-clinical or clinical depression. Similarly, depressive symptoms can increase the risk of developing type 2 diabetes via changes in lifestyle and health-behaviour, as well as endocrinological changes [8], [9]. While some studies indicate a rather linear effect of depression severity on type 2 diabetes [10], others point towards the relevance of assessing subclinical levels of depression as well [11]. This is of relevance, as a diagnosis of depression has been linked to poor outcome [12], [13], low medication adherence and adverse health behaviour in type 2 diabetes [14]. In contrast, in type 1 diabetes depression does not seem to be related to long term outcome of glycemic control [15].
However, while depression is a common psychiatric condition, others, such as personality disorders, pose a higher burden of disease on the individual as well as society due to its chronicity [16].
Common comorbid conditions of depression are personality disorders (PDs) [17]. Personality disorders (PDs) describe enduring maladaptive patterns of emotion, cognition, regulation and behaviour. Patients suffering from a PD are significantly impaired in their psychosocial functioning, which includes difficulties in interpersonal relations as well as self-regulation. PDs pose a high burden on the individual as well as society, and are sometimes experienced as ‘difficult to treat’, especially outside of specialized psychotherapy settings [16], [18], [19]. While there is some evidence for an association between specific forms of PDs and diabetes [20], research on the impact of PDs in diabetes is rare. This is somewhat surprising, as PDs are a significant risk-factor for complications or hospitalizations of patients with diabetes [21]. In one study, a diagnosis of a comorbid borderline personality disorder was related to several disease-specific parameters [22]. In another study, social and relationship functioning, which are key variables for PDs, were interrelated with markers of inflammatory processes in a sample of 200 individuals with type 2 diabetes [23].
Personality variables not directly related to a diagnosis of PD, but to five-factor models of personality, may influence patterns of glycemic control, with mixed findings [24], [25]. To sum up, PDs may be especially harmful in the context of type 2 diabetes via changes in health-behaviour and a resulting lack of compliance. Current models of assessment of PDs stress the importance of capturing the impact of subsyndromal alterations in a subjectś personality functioning as well, as those might already interfere with its capacity to implement and maintain behavioural changes, such as dietetic restrictions in type 2 diabetes. The Alternative Model for the Assessment of Personality Disorders (AMPD) of the Diagnostic and Statistical Manual for Mental Disorders of the American Psychiatric Association (DSM-5) [26] and the mental disorder section of the WHO ICD-11 [27] propose a dimensional model of PD diagnosis that focuses on levels of personality functioning regarding the self and relationships. This approach is in line with empirical data from similar research traditions [28], helps to assess subthreshold conditions, and allows for the development of screening instruments [29], [30].
Therefore, it is reasonable to ask if alterations in personality functioning on a subsyndromal level outside of PDs also have an impact on the course in a chronic disease such as diabetes type 2, possibly due to the subjects’ impairment in regulatory capacities. Consequently, the current study addresses the research question if levels of personality functioning are predictive of severity and course of patients with a first diagnosis of type 2 diabetes talking part in an evidence-based disease management program over and above the impact of depression symptoms. To be more precise, the study aims at the question if depression, personality function, or both will have major impact on changes of HbA1c during a standardized treatment program in diabetes type 2 patients.
Section snippets
Study sample
The study was approved by the institutional review-board of the Medical Association Northrhine, Germany (Id.-Nr.: 2012422). Over a period of 36 months, all patients with a first diagnosis of a type 2 diabetes of a GP outpatient setting were invited to participate in a naturalistic, longitudinal observational study with three measurement time-points (T0 = first type 2 diabetes diagnosis, T1 = three months follow-up, and T2 = six months follow-up). Exclusion criteria were high age (>80 years),
Results
Recruitment took place between January 1st 2013 and July 30th 2015. During this period, 78 patients were newly diagnosed with a type 2 diabetes, all of them meeting the study criteria. Seventy-five patients (96.2% of the sample) gave their informed written consent, five individuals dropped out over the course of the intervention, resulting in 70 subjects with complete data (89.7% of the initial sample). 45.7% of the participants were female (N = 32), with a mean age around 60 years. Most of the
Discussion
In a sample of 70 patients with a first diagnosis of type 2 diabetes, a standardized, evidence based disease-management program resulted in a significant decrease of HbA1c over a period of 6 months. Lower levels of personality functioning, but not depression, were related to a less steep decline of HbA1c. To our best knowledge, this is the first longitudinal study to simultaneously test the impact of both depression and personality functioning on HbA1c during a standardized intervention in this
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Declaration of interest
None.
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Johannes C. Ehrenthal and A. Düx contributed equally.