Type 2 Diabetes Ups Vascular Dementia Risk in Women

Veronica Hackethal, MD

December 29, 2015

People with type 2 diabetes have about a 60% increased risk of dementia compared with those without diabetes, according to a new meta-analysis. The study also found that women with type 2 diabetes are at much higher risk of developing vascular dementia than men with diabetes.

The analysis included data on over 2.3 million people and over 100,000 cases of dementia — more than seven times the data in past reviews on the issue.

"Diabetes increases the risk of developing dementia, but for a major subtype of dementia — namely vascular dementia, not Alzheimer's disease — the risk is higher in women with diabetes compared with men with diabetes," commented senior author Rachel Huxley, DPhil, head of the School of Public Health, Curtin University, Perth, Australia.

"These findings add to the evidence that diabetes confers a greater vascular hazard in women compared with men," she added, "Diabetes confers a greater risk of developing heart disease, stroke, and now vascular dementia in women compared with men."

The study was published online December 17 in Diabetes Care, by Saion Chatterjee of Alfred Health, Melbourne, Australia, and colleagues.

Dementia: A Growing Health Problem

Dementia is a growing health problem. About 44 million people have dementia worldwide, with 7.7 million new cases diagnosed each year. Forecasts predict that the prevalence of dementia will double by 2030 and triple by 2050, according to background information in the article.

The two most common forms of dementia include nonvascular dementia (mainly Alzheimer's disease) and vascular dementia. A past review found that people with diabetes had about a 70% increased risk of dementia, but it was limited by the fact that most of the documented dementia cases were in people of Asian background. It also lacked analyses on sex differences and dementia subtypes.

In this new meta-analysis, Dr Huxley and her team conducted a systematic search for studies published up to November 2014 that prospectively evaluated the link between diabetes and dementia. The researchers asked authors of these studies to supply unpublished results regarding sex-specific relative risks (RR) and the link between diabetes and all types and subtypes of dementia.

They included data from 14 studies, covering 2,310,330 people (48% women) and 102,174 cases of dementia. Asians still comprised 90% of the individuals and 96% of the dementia cases, because the analysis included data from two large Asian studies.

The researchers also standardized the level of adjustment for major vascular risk factors across studies (as far as possible), thereby lessening the possible effect of residual confounding on study estimates and allowing them to examine whether adjustment had a similar effect on the age-adjusted estimates for women and men.

Multiple-adjusted analyses showed that both sexes had around a 60% increased risk of dementia if they had diabetes compared with not having diabetes (women: pooled RR, 1.62; 95% confidence interval [CI], 1.45 – 1.80; men: pooled RR, 1.58; 95% CI, 1.38 – 1.81).

Women With Diabetes at Higher Risk of Dementia

Women with diabetes had 2.3 times the risk of vascular dementia (RR, 2.34), while men with diabetes had 1.7 times the risk of vascular dementia (RR, 1.73) compared with those without diabetes.

Women with diabetes had 1.5 times the risk of nonvascular dementia (RR, 1.53), while men with diabetes had 1.49 time the risk of nonvascular dementia (RR, 1.49) compared with those without diabetes.

Compared with men, women with diabetes had a 19% overall higher risk of vascular dementia (multiple-adjusted ratio of the relative risks [RRR], 1.19; P < .001).

Excluding data from large Asian studies did not change the results, except that the overall increased risk of nonvascular dementia in women compared with men became nonsignificant.

Limitations included variations in methodologies and duration and diagnosis of diabetes and dementia across the included studies. In addition, the meta-analysis could not look at the links between duration of diabetes, glycemic control, and dementia.

The authors suggest that treatment disparities in the management of diabetes — especially inadequate care in women — may play a role in these findings. Accumulating evidence, though, also points to a biological role for the increased diabetes-associated vascular risk in women compared with men.

"More in-depth physiological studies are needed that examine how blood glucose interacts with the vasculature and whether there are any significant sex differences," Dr Huxley concluded.

The authors report no relevant financial relationships.

Diabetes Care. Published online December 17, 2015. Abstract

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