Towards a Better Understanding of Diabetes Distress, Depression and Poor Glycaemic Control in T2DM

Depressive symptoms are assessed using the 20-item Center for Epidemiologic Studies Depression Scale (CES-D), covering 20 symptoms of depression. Frequencies of the symptoms during the past week are scored on a 4-point Likert scale (from 0 - "rarely or non of the time" to 3 - "most or all of the time"). Item scores are summed to a total score ranging from 0 to 60, whereby higher values reflect higher depressive symptoms. A cut-off point at ≥ 22 points (found to have the best likelihood ratio for detecting depression within the German population) is used to establish elevated depressive symptoms in this study.

Diabetes Distress is assessed as using the 20-item Problem Areas In Diabetes Scale (PAID). 20 potential problems related to living with diabetes are rated on a 5-point Likert scale (from 0 - "not a problem" to 4 - "serious problem"). Item scores are summed/transformed to a total score ranging from 0 to 100, whereby higher values reflect higher diabetes distress. A cut-off point at ≥ 40 points is commonly used to establish high diabetes distress, so too in this study.

HbA1c (estimated in %-points; mmol/mol values are calculated thereof) is used as a measure of glycaemic levels during past 3 months. It is estimated from a venous blood sample using high performance liquid chromatography (Tosho G11 analyser; meeting International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) standard) in this study. Higher values indicate less optimal glycaemic control, and values above 7.5% (58 mmol/mol) are considered to indicate glycaemic levels in need of improvement.

Percentage of glucose values measured using CGM ("FreeStyle Libre 2" glucose monitoring system) during 4-week ambulatory assessment which are between 70 and 180 mg/dl (out of all measured values). Note that although the expression "time in range (TIR)" suggests a time measure, this is in fact estimated as a percentage score.

Estimated by the coefficient of variation (range 0 to 1) of all glucose values measured using CGM ("FreeStyle Libre 2" glucose monitoring system) during the 4-week ambulatory assessment phase.

Percentage of glucose values measured using CGM ("FreeStyle Libre 2" glucose monitoring system) during 4-week ambulatory assessment phase which are below 70 mg/dl (out of all measured values). Note that although the expression "time in hypoglycaemia" suggests a time measure, this is in fact estimated as a percentage score.

Percentage of glucose values measured using CGM ("FreeStyle Libre 2" glucose monitoring system) during 4-week ambulatory assessment phase which are over 180 mg/dl (out of all measured values). Note that although the expression "time in hyperglycaemia" suggests a time measure, this is in fact estimated as a percentage score.

Activity time (in h/day) is measured continuously during the 4-week ambulatory assessment phase using a wearable health tracker/wristband ("Garmin vivosmart 4").

Sleep time (in h/day) is measured continuously during the 4-week ambulatory assessment phase using a wearable health tracker/wristband ("Garmin vivosmart 4").

Heart rate (in beats/minute) is measured continuously during the 4-week ambulatory assessment phase using a wearable health tracker/wristband ("Garmin vivosmart 4"). Heart rate variability is calculated thereof using the coefficient of variation.

Sleep quality of the past night is assessed each morning during the 4-week ambulatory assessment phase using items from the Pittsburgh Sleep Quality Index (PSQI) adapted for ecological momentary assessment (EMA). Subjective sleep quality is rated on a 10-point Likert scale (0-"very poor" to 10-"very good"). Further items request total time in bed ("How many hours did you stay in bed last night?"), sleep latency ("How many minutes did it take until you fell asleep?"), number of wake-ups ("How many times did you wake up last night?") and total time awake ("If you woke up, how many minutes did you stay awake in total?"). The following aspects are estimated thereof: sleep quality; sleep latency; sleep duration; sleep efficiency (each scored from 0 to 3; higher scores indicate more problems). The scales are summed to a total from 0 to 12; higher scores reflect lower sleep quality. Scoring of the PSQI is explained elsewhere (https://www.dgsm.de/fachinformationen_frageboegen_psqi.php).

Stress level is assessed four times daily during the 4-week ambulatory assessment phase assessed using the single item "How stressed are you feeling right now?" and a Likert scale from 0 - "not at all stressed" to 10 - "very strongly stressed" in an ecological momentary assessment (EMA) survey via smartphone.

Mood is assessed twice daily during the 4-week ambulatory assessment phase using selected items from the University of Wales Institute of Science and Technology (UWIST) Mood Adjective Checklist (UMACL) in an ecological momentary assessment (EMA) survey via smartphone. 12 of the 29 UMACL items were selected based on their significant associations with glycaemic outcomes from CGM assessment (own data set); each four of them reflect positive and negative hedonic tone and energetic and tense arousal. Responses are given on a four-point Likert scale (0 - "definitely not" / 1 - "slightly not" / 2 - "slightly" / 3 - "definitely) reflecting the presence or absence of each aspects. Item scores are summed/averaged to scale scores (from 0 to 3) reflecting hedonic tone and arousal levels; higher scores reflect higher hedonic tone and arousal levels, respectively.

Mood is assessed twice daily during the 4-week ambulatory assessment phase using selected items from the University of Wales Institute of Science and Technology (UWIST) Mood Adjective Checklist (UMACL) in an ecological momentary assessment (EMA) survey via smartphone. 12 of the 29 UMACL items were selected based on their significant associations with glycaemic outcomes from CGM assessment (own data set); each four of them reflect positive and negative hedonic tone and energetic and tense arousal. Responses are given on a four-point Likert scale (0 - "definitely not" / 1 - "slightly not" / 2 - "slightly" / 3 - "definitely) reflecting the presence or absence of each aspects. Item scores are summed/averaged to scale scores (from 0 to 3) reflecting hedonic tone and arousal levels; higher scores reflect higher hedonic tone and arousal levels, respectively.

Diabetes-specific problems are assessed daily during the 4-week ambulatory assessment phase using six items adapted from the Problem Areas In Diabetes Scale and additional items in an ecological momentary assessment (EMA) survey via smartphone. Responses are given on a Likert scale from 0 - "not at all" to 10 - "very strong". Item scores are averaged to a scale ranging from 0 to 10, whereby higher scores indicate greater problems.

Cortisol level (in μg/dl) is estimated from saliva samples collected at fixed day times (morning; afternoon; late evening) on four consecutive days (Sat/Sun/Mon/Tue) during ambulatory assessment period. Collection date within 4 week-period is from the beginning of the third week (approx. 2 weeks after baseline). Samples are analysed using electrochemiluminescence (Cobas 6000 analyser).

Estimated from venous blood sample (fasting blood collection) in mg/dl.

Estimated from venous blood sample (fasting blood collection) in pg/ml.

Estimated from venous blood sample (fasting blood collection) in pg/ml.

Estimated from venous blood sample (fasting blood collection) in pg/ml.

Coping styles regarding stressful events are assessed at baseline using the 21-item short form of the Coping Inventory for Stressful Situations (CISS-21). The scale enables estimation of three scale scores reflecting task-oriented coping, emotion-oriented coping and avoidance coping (each seven items). Responses are given on a five-point Likert scale (1 - "not at all" to 5 - "very much"). Item scores are summed to scale scores ranging from 7 to 35, whereby higher scores reflect higher use of the corresponding coping style. Note: This outcome variable is assessed to be used as a mediator or moderator or control factor in the analyses of associations between primary and secondary outcome variables (e.g. between diabetes distress and glycaemic levels).

Resilience is assessed at baseline using the Resilience Scale (RS-13). Its 13 items are scored on a 7-point Likert scale (from 1 - "I do not agree" to 7 - "I fully agree"). Item scores are summed to a total score ranging from 13 to 91, whereby higher scores indicate greater resilience. Note: This outcome variable is assessed to be used as a mediator or moderator or control factor in the analyses of associations between primary and secondary outcome variables (e.g. between diabetes distress and glycaemic levels).

Critical life events during the past 12 months are assessed at baseline using the German "Fragebogen zu Kritischen Lebensereignissen (FKL)" (Questionnaire for Critical Life Events FKL). Emotional distress related to each of 27 possible events which occured during the past 12 months is rated on a 3-point scale (from 0 - "not at all distressing" to 2 - "very much distressing"), and scores are summed to a total score reflecting the burden of recent life events (range from 0 to 54, with higher values reflecting higher burden). Note: This outcome variable is assessed to be used as a mediator or moderator or control factor in the analyses of associations between primary and secondary outcome variables (e.g. between diabetes distress and glycaemic levels).

Diabetes acceptance is assessed at baseline using a 10-item short form of the Diabetes Acceptance Scale (DAS). Each items is scored on a 3-point Likert scale from 0 - "never true for me" to 3 - "always tue for me". Items scores are summed to a total score (from 0 to 30); higher scores reflect higher diabetes acceptance. Note: This outcome variable is assessed to be used as a mediator or moderator or control factor in the analyses of associations between primary and secondary outcome variables (e.g. between diabetes distress and glycaemic levels).

Diabetes self-management is assessed at baseline using the revised version of the Diabetes Self-Management Questionnaire (DSMQ), a 27-item scale reflecting different behaviours/activities related to the self-management of the condition during the past eight weeks. Each item is scored on a 4-point Likert scale (from 0 - "does not apply to me" to 3 - "applies to me very much"), and items scores are summed/transformed to a total score (range 0 to 10) reflecting overall diabetes self-management. Note: This outcome variable is assessed to be used as a mediator or moderator or control factor in the analyses of associations between primary and secondary outcome variables (e.g. between diabetes distress and glycaemic levels).

Diabetes-specific problems are assessed at baseline using the Diabetes Distress Scale (DDS), a 17-item scale reflecting diverse problems related to living with diabetes. Items scores (from 1 - "not a problem" to 6 - "a very serious problem") are summed and averaged to a total ranging from 0 to 6 with higher values reflecting more problems. Subscale scores reflecting emotional burden, regimen-related distress, physician-related distress and interpersonal distress can also be calculated. Note: This outcome variable is assessed to be used as a mediator or moderator or control factor in the analyses of associations between primary and secondary outcome variables (e.g. between diabetes distress and glycaemic levels).

Fear of hypoglycaemia is assessed at baseline using the 11-item short form of the Hypoglycaemia Fear Survey-II (HFS-II). The occurence of eleven hypoglycaemia-related worries and avoidance behaviours during the past four weeks is rated on a five-point Likert Scale (0 = never to 4 - "almost always"). Item scores are summed to a total score ranging from 0 to 44, whereby higher values indicate higher fear of hypoglycaemia. Note: This outcome variable is assessed to be used as a mediator or moderator or control factor in the analyses of associations between primary and secondary outcome variables (e.g. between diabetes distress and glycaemic levels).

Fear of diabetes complications is at baseline assessed using a 6-item short form of the Fear of Complications Questionnaire (FCQ). The questionnaire requests the frequencies of worries and fears regarding risks of developing long-term complications of diabetes. Each item is rated on a four-point Likert Scale (0 = never/rarely to 3 - "very often"). Item scores are summed to a total score ranging from 0 to 18, whereby higher values indicate higher fear of diabetes complications. Note: This outcome variable is assessed to be used as a mediator or moderator or control factor in the analyses of associations between primary and secondary outcome variables (e.g. between diabetes distress and glycaemic levels).