Having a longer duration of type 2 diabetes is linked to a higher risk of developing dementia at age 70, according to a new study published in the journal JAMA.
As noted in a Healio article on the study, previous research has shown that having diabetes increases the risk of developing dementia, but only later in life — at or after age 65. But not much research, prior to the new study, has examined whether developing diabetes at an earlier age increases the risk of developing dementia after age 65.
For the latest study, researchers looked at 10,095 UK residents who took part in a general health study. Health records showed which participants developed diabetes, and when, during the course of the study period, which lasted from 1991 to 2016.
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During that period, study participants had six clinical examinations. During the initial study recruitment between 1985 and 1988, participants ranged from 35 to 55 years old. For the purposes of the study, developing diabetes was defined as having a fasting blood glucose level of at least 126 mg/dl in a clinical examination, having doctor-diagnosed diabetes in health records, having use of diabetes medications in health records, or having a hospital record of diabetes.
Early onset of type 2 linked to higher dementia risk
During the study period — an average follow-up period of 31.7 years — 1,710 participants developed diabetes, and 639 developed dementia. The rate of dementia at age 70 was 8.9 per 1,000 person-years for people without diabetes. For people who had developed diabetes up to five years earlier, the dementia rate was 10.0 per 1,000 person-years, or an 11% higher risk for dementia after adjusting for certain differences between the groups. For participants who had developed diabetes six to 10 years earlier, the rate of dementia was 49% higher at age 70. And for participants who had developed diabetes more than 10 years earlier, the rate of dementia was an astonishing 112% higher at age 70 than in participants who didn’t have diabetes.
Upon further examination, the researchers found a linear association between time of diabetes diagnosis and dementia risk — meaning that an earlier diagnosis steadily and predictably increased the risk of developing dementia. At age 70, for every five years earlier a person was diagnosed with diabetes, the risk for dementia increased by 24% after adjusting for demographic factors (like race and income level), reported health behaviors, and other measures of health status.
These findings shouldn’t be surprising, the study authors noted, since developing diabetes at an earlier age has long been known to increase the risk of certain diabetes complications and cardiovascular problems. But this study makes clear that the same pattern applies to dementia — and demonstrates yet another reason why diabetes prevention should be a priority for doctors, patients, and healthcare systems.
Want to learn more about maintaining cognitive health with diabetes? Read “Nine Tips to Keep Your Memory With Diabetes,” “Keeping Your Brain Strong With Diabetes” and “Memory Fitness: How to Get It, How to Keep It.”
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