HONOLULU – Diabetes can be a challenge to control, depression can be difficult to treat and keep in remission, and growing evidence suggests the combination can be especially problematic for patients. And as if this adverse synergy were not bad enough, having these two conditions more than doubles the likelihood that a patient will develop dementia, Dr. Wayne J. Katon said.
Screening all patients with type 2 diabetes for depression, therefore, could have a big impact, he said at the meeting. The American Diabetes Association has endorsed such screening since 2005.
Given the bidirectional relationship between these conditions, physicians treating patients with depression also should assess, counsel, and monitor them for the development of diabetes. “Some of our psychiatric education will be pushing residents to keep up their medical skills to do monitoring. If we only train psychiatrists to do blood pressure monitoring alone, it would make a big difference,” said Dr. Katon, professor of psychiatry and behavioral sciences at the University of Washington in Seattle.
This dual comorbidity puts patients at increased risk for earlier mortality.
Major depression predicts an increased likelihood of cigarette smoking during adolescence (and more difficulty quitting), a sedentary lifestyle, and obesity. Patients with major depression also can feature decreased insulin sensitivity, increased inflammatory markers, and high cortisol levels, which all become risk factors for diabetes and heart disease.
“You can see why you would be at higher risk of earlier mortality,” Dr. Katon said.
Diabetes and depression are independent risk factors for dementia, based on the findings in a prospective study of 3,837 primary care patients (J. Gen. Intern. Med. 2010;25:423-9). “It looks like these are particularly bad conditions to have together in terms of risk of dementia,” he said.
Dr. Katon and his colleagues found that 7.9% of patients with diabetes and major depression developed dementia over a 5-year period (based on ICD-9 codes) compared with 4.8% of those with diabetes alone (fully adjusted hazard ratio, 2.69). “This was not explained by depression being a prodrome for dementia,” he said.
A more than twofold increased risk for dementia is “especially frightening,” Dr. Katon added. “It speaks to the importance of more aggressively screening diabetics for depression and more effectively treating them.”
Beyond having an increased risk of mortality and dementia, people with diabetes and depression also have lower levels of self-care, do not exercise as much, and are not as adherent to medications, compared with nondepressed diabetics (Diabetes Care 2004;27:2154-60).
In this study, those with diabetes and major depression had significantly more nonadherent medication days over time, compared with nondepressed diabetics. “This does not portend well for increased risk of morbidity and mortality,” Dr. Katon said.
Session moderator Dr. Herbert Pardes commented, “This is a big deal. The comorbidity of depression with a major medical condition … people have got to pay attention to the medical health as part of the comorbidities.” Dr. Pardes is president and CEO of the New York Presbyterian Hospital in New York City.
The baseline severity of diabetes (higher number of symptoms) was a strong predictor of a patient having major depression in a 5-year follow-up study (Psychosomatics 2009;50:570-9).
Dr. Katon and his coauthors also found having one or more coronary procedures during the 5 years predicted major depression in this prospective study of 2,759 primary care patients with diabetes.
The study also revealed a higher likelihood for all-cause mortality associated with depression (hazard ratio, 1.53, vs. 1.23 for those without depression). “Diabetics with major depression were about 50% more likely to die than nondepressed diabetics over 5 years,” Dr. Katon said.
After confounders, including cigarette smoking and a sedentary lifestyle were controlled for, major depression was associated with more microvascular complications (HR, 1.33 vs. 1.05); more macrovascular complications (1.38 vs. 1.32), and a higher prevalence of foot ulcers (1.99 vs. 1.22).
Diabetes, depression, and coronary artery disease appear to be one of the “natural clusters of illnesses that doctors see,” Dr. Katon said. These illnesses each have a high prevalence, high comorbidity, and bidirectional adverse interactions.
Depression, chronic pain, and substance abuse comprise another natural cluster, he added “but that is a whole other lecture for another day.”
Dr. Katon said he has received honoraria from Forest Laboratories, Lilly, Pfizer, and Wyeth.