Depressive symptoms, sleep quality and cognitive functioning in outpatients with type 2 diabetes

Diabetes mellitus has become a point of major concern around the world. It is
estimated that the total number of persons with diabetes will increase to 366
million in 2030. Diabetes type 2 accounts for 90-95% of the cases. It is
associated with a variety of secondary complications. Diabetes type 2 can
damage multiple organs including the eyes, kidneys, heart and brain. This
article focuses on brain related complications in diabetes.
Research indicates that cognitive impairment and depression are among the most
common brain related complications in DM. DM patients are 1.5 times more likely
to experience cognitive decline, with research showing that 25.8% of persons
with DM had cognitive impairment. These impairments are consistently found in
the domains of memory, information-processing speed, and attention and
executive functioning. DMT2 is also associated with a high prevalence of
depression. At least 10-30 of DM patients suffer from elevated depressive
symptoms and approximately 10% from a major depressive disorder.
The question arises if depression and cognitive impairment share the same
aetiologies in DMT2: both conditions may have shared risk factors. Research
indicates a few underlying mechanisms for the occurrence of depression in
persons with DMT2 and possible underlying mechanisms for the relationship
between cognitive impairment and depression. An example is, DMT2 is associated
with a decreased insulin production or receptor resistance to insulin in its
target tissues. The central insulin receptors are mainly localised in the
hippocampus, olfactory bulbs and hypothalamus. As a part of the limbic system,
the hippocampus takes part in neuroendocrine responses to emotional stressors.
Under these stressors, the release of acetylcholine in the hippocampus
increases. At the same time the plasma glucose will elevate. As mentioned
before, a high level of glucose can result in accumulation of advanced
glycation end-products, which has a toxic effect on neurons in the brain.
Emotional stressors like depression, activate the amygdala as a part of the
limbic area. Amygdala activation leads to elevated cortisol levels, which is
known as a stress hormone. A high level of cortisol can result in insulin
resistance of the tissue, a decrease in glucose uptake by muscles and plasma
glucose will be elevated. Which can lead to more AGE*s and impaired cognitive
functioning. Besides this example research indicates more possible underlying
mechanisms.
Based on above-mentioned facts, we might assume that there are some underlying
mechanisms or interactions between cognitive functioning and depression in
persons with DMT2. Research on the relation between cognitive impairment and
depression in patients with DMT2 has been conducted several times, but findings
differ. Previous studies were mainly conducted in primary care units and had
important methodological limitations. The prevalence rates of depression and
cognitive impairments were at the lower end of the range of differences between
persons with DMT2 and control group. This indicates that the research group may
not have been an accurate reflection of the diabetic population. This also
accounts for the HbA1c of the participants, participants had mainly well
controlled diabetes in earlier studies. In contrast to primary care, patients
in an out-patient clinic report more depressive symptoms and have higher
comorbidity rates. Based on above-mentioned mechanisms we assume that there is
a negative relationship between depressive symptoms and cognitive functioning
in DMT2 patients.

The aim of this study is to investigate the prevalence of impaired cognitive
functioning in outpatients with DMT2. Second, we will investigate the
relationship between impaired cognitive functions and sociodemographic factors,
clinical features and depressive symptoms.

The following hypotheses will be investigated:
- There is a negative relationship between depressive symptoms and cognitive
functioning
- There is a negative relationship between sleep quality and cognitive
functioning
- The relationship between cognitive functioning and HbA1c is explained by
depressive symptoms and/or sleep quality
- There is a negative relationship between sleep quality and depressive symptoms
- The relationship between subjective cognitive functioning and depressive
symptoms is stronger than the relationship between objective cognitive
functioning and depressive symptoms


The aim of this research is to increase the knowledge about the comorbidity of
diabetes type 2. Research about cognitieve functioning in outpatients with
diabetes type 2 is rare. Findings can give more insight in the identification
of psychosocial or cognitive problems in patients with diabetes. Additional
diagnostics or treatment can be handed and the quality of healthcare will be
improved. Research findings will be shared within the profession.

The nurses of the department of diabetes will make a list of eligable patients.
The researcher will approach these patients with a introduction letter and an
informed consent form. If patients want to participate they receive an
information letter which two questionnaires; PHQ-9 and the PSQI. Additional,
participants attend the hospital for one day in which a neuropsychological
examination will be conducted. Clinical characteristics will be obtained from
medical records (HbA1c, blood pressure, cholesterol, any macrovascular event,
BMI).

The examination starts with a standardized interview in which additional
medical data are collected. A neuropsychological test battery will be
administered, which will adress the domains memory, information-processing
speed and attention and executive functioning. The following tests will be
administered:
- Rey cft
- 15 woordentest
- digit span WAIS-IV-NL
- TMT A/B
- Stroop 1/2/3
- M-WCST
- LFT
- NLV
Thereafter a structured interview about subjective cognition will take place.
The appointment will take about 1.5 hour to complete.

The risk of this study is negligible. Patients can experience fatigue during
the neuropsychological assessment but this is not harmfull for their health.
If scores from assessment indicate problems, patients are only approximated
when they have given permission on their informed consent form.
The obtained findings of this study are important for the profession and
quality of healthcare. Due to the low risk, this research is justified.