SAN DIEGO — In patients with diabetes, there is an association between depression and the risk for cardiovascular disease, kidney disease, and all-cause mortality, according to a study of American veterans.
"Depression is one of the most common conditions associated with chronic disease, including diabetes and chronic kidney disease," said Miklos Zsolt Molnar, MD, from the University of Tennessee in Memphis. And "comorbid depression in diabetes is associated with poor diabetic control and a poorer quality of life."
"Appropriate intervention studies are now needed to determine whether treating depression in patients with diabetes would prevent chronic kidney disease and cardiovascular disease," he said here at Kidney Week 2015.
The investigators assessed more than 3 million veterans with a baseline estimated glomerular filtration rate (eGFR) of at least 60 mL/min per 1.73 m², and identified 933,211 patients with diabetes.
At study enrollment, 340,806 of the patients were suffering from depression. The mean age of the cohort was 65 years, and almost all of the patients were men.
Depressed patients were somewhat younger than those without depression (61 vs 65 years), had a slightly higher eGFR (84 vs 81 mL/min per 1.73 m²), and had more comorbidities at baseline.
During the median follow-up of 7.3 years, 180,343 patients — or 19% of the cohort of patients with diabetes — developed kidney disease.
Dr Molnar and his colleagues assessed the effect of depression using Kaplan–Meier estimates and Cox proportional hazard models.
The presence of depression at study enrollment was associated with a 20% elevation in the risk for incident kidney disease during follow-up, a 35% elevation in the risk for incident stroke, a 24% elevation in the risk for incident coronary heart disease, and a 25% elevation in the risk of all-cause mortality.
Mental and Physical Health
To determine the presence of depression at baseline, the researchers looked at International Statistical Classification of Diseases and Related Health Problems, Ninth Revision (ICD-9) codes and medication. There was no concrete diagnosis of depression, which is a potential limitation of the study, Dr Molnar acknowledged.
In an observational study such as this one, the presence of depression can only be said to be associated with worse cardiovascular and kidney outcomes and cannot be inferred to be causal, he told Medscape Medical News. Nevertheless, others have reported that depressed patients with diabetes have worse diabetes self-care and worse clinical outcomes.
"One potential explanation for our findings is that if a patient is depressed, there is a greater likelihood that they will be nonadherent to their regimens, and that might explain these poorer outcomes," said Dr Molnar.
Depression is also associated with more inflammation, and inflammation is a well-known risk factor for poor outcomes, he added.
Whether or not findings are generalizable to a nonveteran population is unclear at the moment. "However, in general, I don't think we are very good at either diagnosing depression in our patients or treating it," he said.
Depression has been identified as a risk factor for poorer outcomes in patients who have experienced a myocardial infarction, but when the depression was treated, it made no difference in hard clinical end points in these patients, Dr Molnar explained.
It is very important for clinicians to understand the contribution of depression to the development or progression of kidney disease, said session cochair Sriram Narsipur, MD, associate professor of medicine at the State University of New York Upstate Medical University in Syracuse.
"It is the rare patient I see who doesn't have depression, and it ties in with so many things in life," Dr Narsipur told Medscape Medical News. "It ties in with your social network, it ties in with your ability to take your medications, and it ties into your ability to understand and remember the information that your doctor has provided."
"Depression is an absolutely central issue here that we are only touching the surface of, and I applaud the authors of this study for their work in this area," he said.
The study was funded by Veterans Administration Support. Dr Molnar and Dr Narsipur have disclosed no relevant financial relationships.
Kidney Week 2015: American Society of Nephrology Annual Meeting. Abstract TH-OR016. Presented November 6, 2015.
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Cite this: Depressed Diabetes Patients Have More Heart, Kidney Trouble - Medscape - Nov 10, 2015.