Individuals in the 50-64 age category with both diabetes and depression experienced a significant acceleration in memory loss compared to individuals with only one, or neither condition.
Previous research found that having type 2 diabetes increases a person’s risk of developing depression. Conversely, having depression increases a person’s risk of developing diabetes. Both conditions are associated with an increased risk of cognitive decline and dementia.
In a recent study published in PLOS One, researchers from England investigated whether diabetes and depression have a synergistic negative impact on memory and cognition. Their large observational study had a sample of 11, 391 individuals initially grouped by age as those 50-64 and those over 65. Using the eight-item Center for Epidemiological Studies-Depression scale, depression was measured six times between 2002 and 2010. Memory and executive function were measured in two ways. First, participants were asked to recall 10 items on a list both immediately afterwards and then again after having performed other tasks. Second, participants were asked to list as many animals as they could. These two measures were assessed five times over the same eight years. In addition, interviews were conducted biennially. To improve confidence in their findings, the researchers controlled for factors such as age, marital status, socioeconomic class, smoking, levels of physical activity, and alcohol consumption.
To examine if diabetes and depression together have a greater negative impact on memory and cognition, the participants were divided into four exposure categories: 1) no diabetes or evidence of depression, 2) diabetes but no evidence of depression, 3) no diabetes but evidence of depression, and 4) diabetes and evidence of depression.
In terms of group characteristics, participants with both conditions were more likely to be of a lower socioeconomic status, physically inactive, obese, and less likely to drink or be married. Participants with diabetes alone were more likely to be older males with hypertension and participants with only depression were more likely to be female and smokers.
With respect to how these conditions were associated with memory and executive function, they found that individuals in the 50-64 age category with both conditions experienced a significant acceleration in memory loss compared to individuals with one or neither condition. The rate of executive function decline was also significantly greater in those with either one or both conditions compared to those with neither.
The biggest limitation of the study stems from measuring executive function by one’s ability to name animals. This measure may capture memory more than executive function and may be a reflection of other factors such as education, personal interests, or travel experience. An additional limitation was the lack of data on participants history of depression and the medications being taken for depression. Nonetheless, this study confirms what other studies have reported regarding the effects of diabetes and depression on memory loss. Hopefully, specialized programs to combat memory loss will be developed and made readily available for individuals with both conditions.
Written by Debra A. Kellen, PhD