Conference Coverage
HOUSTON—Cardiovascular risk factors in middle age may increase the risk of dementia in later years, according to a subanalysis of a 25-year atherosclerosis study.
Rebecca Gottesman, MD, PhD
Other conditions that significantly increased the likelihood of late-life dementia were hypertension and smoking, both of which augmented the risk by 40%.
Dr. Gottesman’s subanalysis of the biracial Atherosclerosis Risk in Communities-Neurocognitive Study (ARIC-NCS) also identified racial differences in dementia risk. Smoking was a risk factor for dementia in whites, but not in blacks. In addition, although the results were not significantly different by race, diabetes appeared to increase the risk more among blacks than whites, and hypertension increased the risk of dementia more among whites than blacks.
Analyzing Data From a Study of Atherosclerosis
The ARIC study, sponsored by the National Heart, Lung, and Blood Institute, is a prospective epidemiologic study conducted in four US communities. ARIC is designed to investigate the causes and clinical outcomes of atherosclerosis, and variation in cardiovascular risk factors, medical care, and disease by race, gender, location, and date. The ARIC project has led to the publication of more than 1,700 articles in peer-reviewed journals to date.
A total of 15,792 participants have received an extensive examination, including medical, social, and demographic data. The first screen occurred between 1987 and 1989, and participants were reexamined every three years through 1998, and then again 15 years later. Follow-up occurs yearly by telephone to maintain contact with participants and to assess the health status of the cohort.
The ARIC-NCS study includes about 10,000 of the ARIC participants. Of these patients, 6,471 completed the fifth visit, which occurred during 2011–2013. The participants have undergone cognitive and neurologic assessments to diagnose mild cognitive impairment or dementia and assign an etiology for any cognitive disorder; some also have undergone brain imaging. Last year, investigators published preliminary findings from the study, including that approximately 30% of participants had received a diagnosis of dementia or mild cognitive impairment.
Dr. Gottesman sought to determine the extent to which these subjects’ baseline cardiovascular risk factors influenced their risk of cognitive decline or dementia. She assessed risk for the entire cohort, and then assessed the risk for black and white subjects separately.
Genetic Status Had Largest Effect
In all, 1,516 participants (23%) developed dementia. In the total cohort, dementia was significantly associated with increasing age. Subjects between ages 50 and 54 when first examined had twice the risk of dementia during follow-up, compared with younger subjects, while those between ages 60 and 66 had eight times greater risk. Black race conferred an increased risk, compared with white race (hazard ratio [HR], 1.3). Education of less than a high school degree was associated with a 40% increased risk of dementia. Having at least one copy of the APOE4 allele doubled the risk of dementia.
Increasing BMI did not increase the risk of dementia, Dr. Gottesman noted. Smoking, however, increased the risk of dementia by 40%, as did prehypertension and hypertension. Dyslipidemia was not associated with any increased risk. Diabetes increased the risk of dementia by 80%.
Dr. Gottesman found significant differences in the way the factors affected risk in white and black subjects. Age exerted a greater influence on dementia risk in whites than it did in blacks. The risk was approximately doubled in both groups for people between ages 50 and 54 at baseline. But for patients between ages 55 and 59 at baseline, dementia risk was significantly higher in whites than in blacks (HR, 4.4 vs 3.5). The risk differential was even greater between whites and blacks who were between ages 60 and 66 (HR, 9.5 vs 6.2).
Blacks with low education had a greater risk of dementia than did whites (HR, 1.6 vs 1.3). APOE4 status (ie, having at least one allele) more than doubled the risk of dementia for whites (HR, 2.2), but had a weaker effect in blacks (HR, 1.6).
Obesity increased the risk of dementia by 22% for whites, 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 had a greater effect among whites, increasing the risk by 35%, compared with a nonsignificant 17% increase for blacks, but the difference was not statistically significant. 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%), but the racial difference was not statistically significant.
“We do not have a clear explanation of these disparities in dementia risk with regard to race,” said Dr. Gottesman. “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.”
—Michelle G. Sullivan
Suggested Reading
Baumgart M, Snyder HM, Carrillo MC, et al. Summary of the evidence on modifiable risk factors for cognitive decline and dementia: A population-based perspective. Alzheimers Dement. 2015;11(6):718-726.
Exalto LG, Quesenberry CP, Barnes D, et al. Midlife risk score for the prediction of dementia four decades later. Alzheimers Dement. 2014;10(5):562-570.
Hessler JB, Ander KH, Brönner M, et al. Predicting dementia in primary care patients with a cardiovascular health metric: a prospective population-based study. BMC Neurol. 2016;16:116.
Knopman DS, Gottesman RF, Sharrett AR, et al. Mild cognitive impairment and dementia prevalence: The Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS). Alzheimers Dement (Amst). 2016;2:1-11.
Virta JJ, Heikkilä K, Perola M, et al. Midlife cardiovascular risk factors and late cognitive impairment. Eur J Epidemiol. 2013;28(5):405-416.