HOUSTON – Cardiovascular risk factors present in middle age may presage dementia in later years, a subanalysis of a 25-year atherosclerosis study has determined.
Diabetes conferred the greatest dementia risk, nearly doubling the chance of dementia, Rebecca Gottesman, MD, PhD, said at the International Stroke Conference, sponsored by the American Heart Association.
“In fact, the risk associated with diabetes nears the increased risk associated with having an APOE4 [apolipoprotein E epsilon 4] allele,” saidof Johns Hopkins University, Baltimore.
Her subanalysis of the biracial ARIC-NCS (Atherosclerosis Risk in Communities Neurocognitive Study) also identified some racial differences in risk, with blacks being more vulnerable to the risk imposed by diabetes, and whites more vulnerable to the hypertension-associated risk.
The, sponsored by the National Heart, Lung, and Blood Institute, is a prospective epidemiologic study conducted in four U.S. communities. ARIC is designed to investigate the causes of atherosclerosis and its clinical outcomes, and variation in cardiovascular risk factors, medical care, and disease by race, gender, location, and date. To date, the ARIC project has published over 800 articles in peer-reviewed journals. A total of 15,792 participants received an extensive examination, including medical, social, and demographic data. These participants were reexamined every 3 years with the first screen occurring in 1987-1989. Follow-up occurs yearly by telephone to maintain contact with participants and to assess the health status of the cohort.
comprises about 10,000 of these subjects. Of these, 6,471 completed the fifth visit, which occurred during 2011-2013. They have undergone cognitive, neurologic, and brain imaging assessments to diagnose mild cognitive impairment or dementia and assign an etiology for the cognitive disorder. Last year, investigators published the study’s primary findings: Nearly 30% had a diagnosis of either dementia or mild cognitive impairment.
Dr. Gottesman sought to determine the extent to which these subjects’ baseline cardiovascular risk factors influenced their chances of cognitive decline or dementia. She assessed risk for the entire cohort, and then for black and white subjects separately.
Dementia was present in 1,516 cases (23%). In the total cohort, dementia was – not surprisingly – significantly associated with increasing age. Subjects aged 50-54 years had twice the risk for dementia when compared with younger subjects, while those aged 60-66 years had eight times greater risk. Black race conferred a 30% increased risk, compared with white race (hazard ratio, 1.3). Education of less than a high school degree was associated with a 40% increased risk. Having at least one copy of the APOE4 allele doubled the risk.
Diabetes was second only to genetic status, increasing the risk by 80%.
Dr. Gottesman then divided the cohort by race and reexamined these risk factors separately. She found some significant differences in the way these factors affected risk in white and black subjects.
Age exerted a greater influence on dementia risks in whites than it did in blacks. The risk was about doubled in both groups for people aged 50-54 years. But at age 55-59 years, it was significantly higher in whites than in blacks (HR, 4.37 vs. 3.53). The risk differential was even greater between whites and blacks aged 60-66 years (HR, 9.5 vs. 6.2).
Blacks with low education were more vulnerable to dementia than were whites (HR, 1.6 vs. 1.29). APOE4 status (at least one allele) more than doubled the risk of dementia for whites (HR, 2.23) but was not as strong in blacks (HR, 1.61).
Obesity was riskier for whites, increasing the risk of dementia by 22%, but it had no influence on risk among blacks. Current smoking increased the risk for whites by 62% but was not a significant risk factor for blacks. Prehypertension also affected whites more, increasing the risk by 35%, compared with a nonsignificant 17% for blacks. Full-blown hypertension increased the risk of dementia similarly in both groups (37% and 36%, respectively).
Diabetes increased the risk of dementia more in blacks than it did in whites (85% vs. 69%).
“We don’t have a clear explanation of these disparities in dementia risk with regard to race,” Dr. Gottesman said. “It could be, though, that even if a risk factor has the same relationship with dementia in both groups, if it is more prevalent in one group, that may somewhat account for this larger population attributable risk.”
She had no financial disclosures.