By Brandon May
NEW YORK (Reuters Health) - A new study shows dementia risk follows a U-shape curve after a diagnosis of type-2 diabetes, dropping for nearly five years and then rising again with longer disease duration.
"We identified a non-linear association of type 2 diabetes duration and the risk of dementia. Physicians should closely monitor cognitive function in diabetic patients beyond the first few years after diagnosis, because the later increase in dementia occurred in all treatment groups," Dr. Constantin Reinke of the University of Rostock, in Germany, and colleagues write in Age and Ageing.
In recent decades, the global prevalence of both diabetes and dementia has increased. Cardiovascular risk factors are the main drivers of an increased dementia risk in midlife, but diabetes appears to be the strongest predictor among the cardiovascular risk factors for dementia in later life, the researchers note.
To examine the link between diabetes duration and dementia risk, they analyzed claims data on 13,761 people in Germany who were older than 64 years and had a new diagnosis of type-2 diabetes, with at least one quarter of a year of follow-up. Mean age at diabetes diagnosis was 76.9 years.
To estimate dementia risk, the researchers used piecewise exponential models with a linear and a quadratic term for the period since the index diabetes diagnosis. They used the Adopted Diabetes Complications Severity Index to control for diabetes severity in the analysis.
There were 2,558 incident cases of dementia through 2014, 2,845 people died and 8,544 reached the end of follow-up (mean follow-up per patient, 4.18 years).
One year after diabetes diagnosis, dementia risk had decreased by 26%. For the next three years, it remained nearly constant, reaching a minimum after 4.75 years and then rising again through the end of follow-up.
"Interaction between the duration of (type-2 diabetes) and different treatment strategies did not change the U-pattern for three of four treatment strategies and disclosed the strongest U-shape for insulin treatment. Only the group with mixed treatment strategy did not reveal a clear U-pattern," the researchers report.
Dr. Leann Olansky, an endocrinologist at Cleveland Clinic, in Ohio, who wasn't involved in the study, suggested that metformin was likely included in many of the patients' treatment regimens at the beginning of their disease.
"This therapy is known to protect against dementia," she told Reuters Health by email. "On the other hand, hypoglycemia is known to increase dementia (risk), so sulfonylurea agents and insulin might be added later and could explain the increase after the first few years."
Dr. Sevil Yasar, an associate professor of medicine at Johns Hopkins University School of Medicine in Baltimore, Maryland, said lifestyle changes that may follow after diagnosis, such as more exercise and weight loss, may be protective of dementia, explaining the initial dip in risk.
"The other thing is that people (with diabetes) are being aggressively treated and maybe that could be the short-term benefits of the dementia-risk reduction," she told Reuters Health by phone.
Despite these potential short-term benefits, the "vascular changes start to occur no matter how well diabetes is treated," added Dr. Yasar, who also wasn't involved in the study. She also noted that compliance with therapy tends to decline over time, which might also help explain the increased risk for dementia and other comorbid conditions.
Dr. Reinke was not immediately available for comment.
SOURCE: https://bit.ly/3HK1FmF Age and Ageing, online December 7, 2021.