Depression + Diabetes = Dementia?

Previous studies suggest that depression and type-2 diabetes are separate risk factors for dementia, but whether an additive effect exists has been unclear.  Dimitry Davydow, from the University of Washington School of Medicine (Washington, USA), and colleagues utilized data collected in 2,454,532 Danish adults, ages 50 years and older, including those with depression (19.4%), type-2 diabetes (9.1%), or depression and type-2 diabetes (3.9%).  The average age at initial diagnosis of type 2 diabetes was 63.1 years old and the average age at initial diagnosis of depression was 58.5 years old.  Data analysis revealed that during the study period, 2.4% of the participants developed dementia and the average age at diagnosis was nearly 81 years. Of those individuals who developed dementia, 26.4% had depression alone and10.8% had type 2 diabetes alone, with 6.7% having both conditions.  The results of the study indicate that type 2 diabetes alone was associated with a 20% greater risk for dementia and depression alone was associated with an 83% greater risk, while having both depression and type-2 diabetes was associated with a 117% greater risk. The risk for dementia appeared to be even greater among those study participants younger than 65 years.  The study authors warn that: “Depression and [type-2 diabetes] were independently associated with a greater risk for dementia, and the combined association of both exposures with the risk for all-cause dementia was stronger than the additive association.”