Depression - whether it's mild or severe - can significantly raise the risk of dying for people with type 2 diabetes, research shows.
A study in the journal Diabetes Care found that people who have the combination of type 2 diabetes and minor depression have a 67% greater risk of dying, while people with both diabetes and major depression have a 130% greater chance of dying, compared to those who have type 2 diabetes alone.
Researchers at the University of Washington followed 4,154 people who had type 2 diabetes for three years after they filled out a questionnaire screening for depression. Participants were considered to have minor depression if they reported two to four symptoms of depression that lasted the greater part of two weeks or major depression if they had at least five symptoms over the same length of time.
In order for a person to be considered depressed, the reported symptoms had to include depressed mood or loss of pleasure. Other known symptoms of depression include changes in sleeping and eating habits, lack of energy and changes in activity levels.
Based on the criteria, 354 participants were considered to have minor depression and 497 participants were classified as having major depression at the start of the study. Participants with minor depression were less educated and less likely to be Caucasian, while those with major depression were younger, less likely to be married, and more likely to be female than the participants who did not report symptoms of depression.
Participants with depression were also more likely to have two or more complications related to diabetes, to have another medical condition, to smoke, to be obese, and to have been treated with insulin. They were also less likely to be physically active.
During the three years of follow-up, 382 participants died from all causes. But a greater proportion of participants with depression died compared to those who weren't depressed: nearly 14% of those with minor depression and 12% of those with major depression died, while slightly more than 8% of non-depressed participants died.
While the study doesn't pinpoint the reason the combination of depression and type 2 diabetes appears to be more deadly than diabetes alone, the researchers say the cause could be biological or behavioural.
For example, previous work by the study's lead researcher, Dr. Wayne J. Katon, found that patients with both depression and diabetes are less likely to follow diet and exercise recommendations, to check their blood sugar levels or to fill their prescriptions for blood sugar, cholesterol or blood pressure medications. They were also more likely to have at least three risk factors for heart disease, including smoking, obesity and a sedentary lifestyle, compared to patients who had diabetes alone.
Furthermore, they add that changes in brain chemistry and the nervous system which accompany depression could also worsen diabetes outcomes.
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