This blog is coming across the woodland in stereo as the Diabetes and Mental Elf join forces. In 2011 the Diabetes Elf highlighted Depression and Diabetes: a two way street? a systematic review looking at cause and effect of diabetes and depression and the link between diabetes and cardiovascular disease is not contested.

However moving forward from this, in the Netherlands Van Dooren and colleagues have completed a systematic review and meta-analysis looking at the question: does depression increase the risk for all-cause (and cardiovascular mortality) in people with diabetes? The results were published in PLOS ONE in March of this year.

Methods

A literature search was completed using PubMed and PSYCHinfo and studies that met the following criteria were included:

1. Longitudinal studies, including both retrospective and prospective
2. The study population included people diagnosed with diabetes (clinical or self-report)
3. The outcome variable was mortality
4. Association between baseline depression (yes/no, clinical diagnosis or self-report) and mortality during follow up was analysed

400 papers were originally identified, however with the screening and eligibility criteria employed this reduced dramatically to only 16 studies. The number of individuals included in these studies was impressive though, at 109,046, with 21,443 (19.7%) identified as having comorbid depression.

Results

• 75% of studies showed a significant association between depression and mortality in individuals with diabetes
• Compared to those without depression, depressed individuals with diabetes had a 46% increased risk for all-cause mortality

Although based on only 5 studies, the results also show a 39% increased risk for cardiovascular mortality associated with the presence of depression in diabetes

There was however a high heterogeneity in the studies. Subgroup analyses twere performed and there was no significant differences for follow-up length, age, method of depression assessment, method of diabetes assessment, number of participants and the percentage of females included.

Conclusion

Depression is associated with a 1.5-fold increased risk of all-cause mortality in people with diabetes

Although based on only five studies, similar results were found for cardiovascular mortality. Whilst considering the study limitations and strengths, the authors believe that this could be an accurate risk estimation.

Only one article reported on individuals with type 1 diabetes, and two articles reported on a combined study population of people with both type 1 and type 2 diabetes. Because type 2 diabetes is the most prevalent form of diabetes, cohort studies with patients with type 1 diabetes are scarce.

Finally, the authors found an indication of publication bias: negative or insignificant result are often not submitted for publication by authors, or rejected by reviewers and editors. Another good example of why you should sign up to the AllTrials campaign that the Mental Elf blogged about last month.

Recommendations

1. Future studies are encouraged to explore whether the association between depression and mortality is similar for people with type 1 and type 2 diabetes
2. Future studies to address the behavioral or physiological pathways that may explain this association
3. Screening for depression in clinical practice may be a helpful first step, and should be embedded in collaborative care approaches

So out in the woodland we Elves have enjoyed this collaboration, after all we do want the same thing.

Links

Fleur E. P. van Dooren, Giesje Nefs, Miranda T. Schram, Frans R.J.Verhey, Johan Denollet, François Pouwer. Depression and Risk of Mortality in People with Diabetes Mellitus: A Systematic Review and Meta-Analysis. PLOS ONE March 2013, Vol 8, Issue 3.