J-shaped Link Between Diabetes Duration and Depression

Liam Davenport

January 22, 2016

The risk of depression following a diagnosis of diabetes falls during the second decade of having the disease and then rapidly rises, Australian researchers have discovered, in a study that suggests there is a J-shaped relationship between the two conditions.

They found that living with diabetes initially doubles the risk of depression. Treatment and disease acceptance may then contribute to a lower likelihood of depressive symptoms, before the risk is almost tripled after the third decade.

The team, led by Osvaldo P Almeida, PhD, from the School of Psychiatry & Clinical Neurosciences, University of Western Australia, Perth, believe that frailty may explain some of the association between diabetes and depression and that the "introduction of strategies that are effective at decreasing diabetes-related complications may also contribute to decrease the risk of depression among older men."

The research was published online in Maturitas on January 11.

Commenting, Dimitry S Davydow, MD, MPH, associate professor in the department of psychiatry and behavioral sciences at the University of Washington School of Medicine, Seattle, said that the study is "very interesting."

He continued: "There's lots of research that's previously found, essentially, that diabetes and depression share a bidirectional relationship, meaning that depression earlier in life raises your risk of a lot of things: not exercising, smoking, and obesity and [factors]...that lead to developing diabetes."

"Conversely, diabetes and diabetes-related complications can raise your risk of developing depression."

Nevertheless, Dr Davydow noted that — as acknowledged by the authors — there are a number of limitations to this study, principally the fact that it was cross-sectional in nature. This means that depression and diabetes were assessed at a single point in time, raising the risk of recall bias when the participants were asked about prior depression.

Living With Diabetes for More Than 30 Years Triples Risk of Depression

The investigators conducted their cross-sectional, community study of 5462 men aged 70 to 89 years living in the metropolitan area of Perth, Australia.

The presence of diabetes was determined by self-reported history, a fasting glucose ≥7 mmol/L, or the use of insulin or hypoglycemic drugs — the researchers did not differentiate between type 1 and type 2 diabetes.

Current depression was assessed using the abbreviated Geriatric Depression Scale, with "ever depressed" including both current depression and a reported history or treatment for depression.

Current depression was identified in 353 (6.5%) of the participants, while 623 (11.4%) were deemed to have had previous depression, giving a total of 976 (17.9%) who were ever depressed.

Diabetes was associated with an increased risk of both ever depression, at an odds ratio of 1.49, and current depression, at an odds ratio of 1.94.

Interestingly, the association between the time lived with diabetes and the risk of current depression revealed a J-shaped curve, at odds ratios for less than 10, 10 to 19.9, 20 to 29.9, and 30 or more years of living with diabetes of 1.92, 1.56, 2.49, and 3.13, respectively, compared with older men without diabetes.

The team found that the strength of the relationship between diabetes and depression was reduced after taking into account frailty, age group, place of birth, education, and smoking history. However, the nature of the association was not altered.

They suggest that the J-shaped relationship they identified between time lived with diabetes and depression may indicate that patients initially experience mental-health benefits from both treatment and illness acceptance.

Dr Davydow agrees that this may be a factor, as diabetes involves "a lot of intensive self-care" to make sure that complications do not develop, which becomes more challenging as time goes on.

However, he reemphasized that the study being cross-sectional means that "you can't really say that much about the 'why,' in that there are lots of possibilities."

For example, a lot of people have a preexisting history of depression prior to diabetes and, over time, during their diabetes, "they're more likely to have recurrences of depression that interfere with their ability to care for themselves," he explained.

This can then lead to a vicious circle of greater complications of the diabetes — such as diabetic neuropathy and possible limb amputation, renal damage and dialysis, and/or diabetic retinopathy — which then cause more depression because of the limitations in functioning that the complications can cause.

Frailty Could Explain Some of the Association

Further analyses by the authors indicated that frailty may explain some of the association between diabetes duration and depression.

A history of diabetes increased the risk of frailty independently of the number of years lived with diabetes, at an odds ratio of 1.1 to 1.2. Furthermore, frailty increased the risk of depression, at an odds ratio of 8.57.

They estimate that, overall, approximately 15% of the association between diabetes and depression may be mediated by frailty.

However, Dr Davydow believes that, at this stage and given the cross-sectional nature of the study, this is speculation.

Nevertheless, it is a "reasonable" assumption, as being frail could increase the likelihood of suffering diabetes complications, which in turn could increase the risk of developing depression.

A more definitive answer on the connection between diabetes, frailty, and depression would, however, require longer and larger studies to be able to "disentangle" the relationship, he said.

In the meantime, he said, "Is this something that we can do something about? Can we find ways to help older adults with diabetes to be more physically active, assist them in taking care of themselves…and also identify depression and treat it so they don't end up having worse long-term complications?"

This work was funded through competitive project grants from the National Health and Medical Research Council of Australia. The authors declare they have no relevant financial relationships.

Maturitas. Published online January 11, 2016. Abstract

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