Type D personality and its impact on patients with Type 2 diabetes mellitus

Background: Type D personality (TDP) has been recognized as a risk factor for many diseases. Researches in association with TDP and type 2 diabetes mellitus (T2DM) were limited. Aims: The aim of this study was to estimate the prevalence of TDP, also to assess the relationship between TDP and perceived stress, self-efficacy, self-care behaviors, and psychological distress on Taiwanese patients with T2DM. Methods: 198 patients with T2DM were recruited consecutively from the department of endocrinology of a regional hospital in Taipei, Taiwan from December 2017 to April 2018. The participants completed questionnaires containing questions about sociodemographic characteristics, TDP, illness-related stress, self-efficacy, execution of diabetes management and emotional distress. Their medical records were reviewed for biomedical data. Results: 41.4% of the 198 patients had TDP. Controlling for sociodemographic factors, patients with TDP were reported significantly poorer on glycemic control than those without this personality ( P <0.05). Compared to those without TDP, the results showed significantly higher levels of perceived stress ( P <0.001) and psychological distress (anxiety and depression) ( P <0.001), as well as significantly lower levels of self-efficacy ( P <0.001) and self-care behaviors ( P <0.001) on patients with TDP. TDP is positively correlated with perceived stress and psychological distress. It is negatively correlated with self-efficacy and self-care behavior scores. Discussion: This study provides the evidence linking TDP with poor glycemic control, self-efficacy, and self-care behaviors, as well as high perceived stress and psychological distress, which highlights the screening of TDP and the specific needs for the care among T2DM patients with TDP.


Background
Among different personality traits, Type D personality (TDP) describes those individuals who simultaneously experience high levels of both two personality traits, negative affectivity (NA), which is the tendency to experience negative emotions across time and situations, as well as the social inhibition (SI), which is the tendency of the self-expression emotion inhibitor for the fears of others' reactions during social interactions [1][2][3] . TDP is considered as psychological risk factors in many diseases. Existing evidences showed that standard biomedical risk factors, such as blood pressure, cholesterol level, obesity and poor cardiovascular outcome, are significantly related to TDP [4][5][6][7][8] . Researches in association with TDP and type 2 diabetes mellitus (T2DM) were limited.
It is known that self-efficacy, self-care behavior, perceived stress, and psychological distress play important roles in psychological aspects of diabetes care. Self-efficacy is defined as the belief in one's capabilities to organize and execute the courses of action that required to produce the given achievement 9 . Strong self-efficacy has been associated with better self-management behaviors in diabetes, including the control of dietary habits, exercise, blood glucose testing, and medication compliance 10,11 . Poor self-efficacy has been associated with increased depressive symptoms and poor glycemic control 12 .
Obviously, self-efficacy affects glycemic control and the outcome of diabetes.
Diabetes is often accompanied with psychological distress and stress. There is a significantly higher prevalence of depression and anxiety on T2DM patients than the general population 13,14 . Psychological distress affects treatment choices, selfmanagement, and outcomes on these patients [15][16][17] . Additionally, researches on T2DM individuals showed that perceived stress disrupts diabetes control indirectly through effects on diet, exercise, and their self-care behaviors, which causes problems in the effective management of diabetes 18,19 .
In our study, we tried to confirm the impact of TDP in relation to the importance of sociopsychological factors on T2DM patients, such as self-efficacy, self-care behaviors, perceived stress and psychological distress.

Study setting and participants
The study was approved by the ethics committee of the regional hospital. Participants who visited the endocrine clinics of the regional hospital, in Taipei, were recruited consecutively from the outpatients between December 2017 and April 2018. The participants were provided with both written consent and oral information regarding the study, who were also informed that they were free to withdraw from the study at any time.
The study was conducted in accordance with the Declaration of Helsinki.
According to the diagnostic criteria of American Diabetes Association (2016), all the participants were diagnosed as T2DM who were at least 20 years of age, and were receiving regular anti-diabetic treatment. Each one was willing and was able to complete the questionnaire. The following exclusion criteria were applied to the study: participants having concurrent malignant tumors, type 1 or gestational diabetes, late stage of cardiovascular, renal diseases or acute complications, severe neurocognitive disorders or psychiatric illness (such as schizophrenia), and who were taking antidepressants.

Data collection
Under the guidance of the trained staff, the eligible subjects were firstly asked to complete the structured questionnaire, that contains demographic and socioeconomic data in a quiet environment, and then five-scale questionnaires (TDP, self-efficacy, self-care behaviors, perceived stress and psychological distress scales). Each one completed the scales without mandatorily stipulated time. Their medical records were reviewed to obtain and confirm information on the medical history, treatment and present glycosylated hemoglobin (HbA1c) level in the past 3 months.

Type D personality (TDP)
TDP was assessed by using Type D Scale-14, Taiwanese version-revised (DS14-TR) 2,20 , which is consisted of two 7-item subscales to measure NA and SI, respectively. Items are scored on a 5-point Likert scale ranging from 0 (false) to 4 (true), with a total subscale score ranging from 0 and 28. TDP was determined while both subscales score 10 points or higher. Both subscales have been tested previously to be internally consistent (Cronbach's α=0.87 and 0.83 for NA and SI, respectively) on T2DM patients 21 .

Self-efficacy
We used the Chinese Version of Diabetes Management Self-Efficacy Scale (C-DMSES), developed by Vivienne Wu et al 22 in 2008. It contains 20 items that reflect the multiple aspects of self-efficacy on diabetes patients, including diet control, physical activity, symptom management, and role function. Each item is on a score from 0 (no confidence at all) to 10 (full confidence), with a total score between 0 and 200. The total score of the 20 items indicates the level of self-efficacy. A higher score reflects better self-efficacy. The Cronbach's α value of the scale was previously estimated at 0.95 22 .

Self-care behaviors
We used the Chinese Version of Diabetes Self-Care Scale (C-DSC), designed by Hurley et al 23 in 1992 and modified by Wang et al 24 in 1998, to assess five domains of a patient's self-care behaviors to manage diabetes, which include diet control, physical activity, medication compliance and glucose monitoring, prevention of diabetic foot ,and treatment of hyper/hypo-glycemia. It contains 26 items and each item is scored on a 5-point Likert scale from 1 (totally disagree) to 5 (totally agree), with a total score between 26 to 130. A higher score indicates better self-care behaviors. The Cronbach's α value of the scale is between 0.82 and 0.92 24 .

Perceived stress
We used the Chinese Version of Problem Area in Diabetes (PAID-C) designed by Polonsky et al 25

Statistical analysis
The data were collected and entered into the computer by a trained staff. The Cronbach's α values were calculated to assess the internal consistency of these scales. Numeric values were presented as mean±standard deviation (SD), with categorical values as n (%).
The differences in the demographic and socioeconomic characteristics between T2DM patients with TDP and non-TDP were compared by the independent sample t-test (for continuous variables) and the chi-square test (for categorical variables). The associations of TDP and psychological variables of T2DM were tested by Bi-serial correlation and pearson product-moment correlation. A P-value of <0.05 was considered statistically significant. All statistical analysis was performed by the SPSS statistical software (version 22.0, IBM Corp., Armonk, NY, USA).

Results
In the study, 82 (41.6%) of the 198 participants had TDP. Table 1 is the demographic, social, and clinical characteristics of the participant with and without TDP. There were no significant differences between the two groups in the distributions of gender, age, body mass index (BMI), T2DM duration, smoking/drinking history, education level, marital status, employment status, current treatment, and major complications. It was important to note that the group with TDP had significantly higher percentage in numbers of high HbA1c level than the non-TDP, which indicated that TDP had poorer glycemic control than non-TDP. Table 2 shows the comparisons of the perceived stress, self-efficacy, self-care behaviors, and psychological distress scores on T2DM patients with and without TDP. TDP had significantly higher scores on perceived stress and psychological distress, but who had significantly lower scores on self-efficacy and self-care behaviors than non-TDP.  32 . It may be because that the T2DM patients in our study were mostly middle-age (51.2±11.0) and had the high educational levels, which led them to express more health awareness and attitudes through these questionnaires.
As is shown Table 1, the demographic and social characteristics had no difference between TDP and non-TDP, which was consistent with the previous reports [1][2][3]29 .
Importantly, we found that HbA1c levels were significantly higher on the patients with TDP than those with non-TDP, which was consistent with the studies by Li X et al 33 and Shao Y et al 34 . Therefore, T2DM patients with TDP tend to have poor glycemic control.
As is shown Table 2, T2DM patients with TDP were more likely to perceive more diabetesrelated stress and experience more psychological distresses (anxiety and depression). They had lower levels of self-efficacy and self-care behaviors to manage their diabetes.
As is shown Table 3, TDP had significantly positive correlations with perceived stress and psychological distress. It had significantly negative correlations with self-efficacy and selfcare behaviors in T2DM patients.
The results of our study indicated that TDP plays an important predictor of self-efficacy, self-care behaviors, perceived stress and psychological distress on T2DM patients.

Limitations
There were some limitations in our study. First, the sample was small, and it was collected from the outpatients who visited the endocrine clinics of a single hospital, which cannot be directly generalized to be the normal population with T2DM or those with more complicated diseases. Second, our design of study was cross-sectional and self-reported.
Our findings may have subjective reporting biases.

Conclusion
We demonstrated that TDP was a crucial predictor of self-efficacy, self-care behaviors, perceived stress and psychological distress on T2DM patients. Our study provided the evidence linking TDP with poor glycemic control, self-efficacy, and self-care behaviors, as well as high perceived stress and psychological distress. We suggested it was necessary to have TDP screening mechanism among T2DM, also to tailor-made specific needs of care for those with TDP.

Declarations
Ethics approval and consent to participate: The Taiwan Adventist Hospital Ethics Committee approved this study(106-E-26). All participants gave written informed consent before data collection began. Consent for publication: All participants gave written informed consent for publication.
Availability of data and materials: The datasets generated and analysed during the current study are not publicly available due to personal privacy but are available from the corresponding author on reasonable request.
Competing interests: The authors declare that there are no competing interests. Di-An Chen also had substantial contributions to acquisition of data.
Chemin Lin also had substantial contributions to interpretation of data.
Acknowledgements: The authors would like to thank all the people with T2DM who participated in this study. The authors also are grateful to the hospital officials for providing support for this study and Sabina Wang for revision of the English.

Abbreviations
Type D personality, TDP; type 2 diabetes mellitus, T2DM; glycosylated hemoglobin, HbA1c; body mass index, BMI; oral antidiabetic drug, OAD; glucagon like peptide-1 receptor agonist, GLP-1 RA; self-efficacy, SE; self-care behavior, SC; negative affectivity, NA; social inhibition , SI.  Table 3 Correlations between Type D personality (TDP), perceived stress, self-efficacy, self-care behaviors, and psychological distress scores: TDP had significantly positive correlations with perceived stress and psychological distress, but it had significantly negative correlations with self-efficacy and self-care behaviors on T2DM patients.