The presence of hypertension or diabetes in African American adolescents as young as 12 years old is associated with a higher risk for late-life cognitive decline, new research suggests.
The new analyses were based on data from the Study of Healthy Aging in African Americans (STAR), which included more than 700 participants.
“We want to make sure that efforts to reduce cardiovascular disease risk factors include young people because they may be at high risk for worse cognitive outcomes later in life,” study author Kristen George, PhD, postdoctoral scholar, Whitmer Lab, University of California, Davis, told Medscape Medical News.
The results were presented at the Alzheimer’s Association International Conference (AAIC) 2020, held online this year because of the COVID-19 pandemic.
Compared with other ethnic groups, African Americans have been shown to have more cardiovascular disease (CVD) risk factors from adolescence to adulthood, and a higher risk for dementia later in life.
However, it has been unclear whether CVD risk factors that develop prior to midlife are associated with late-life cognition.
From 1964 to 1984, Kaiser Permanente Northern California collected information on lifestyle and clinical factors at regular Multiphasic Health Check-ups (MHCs).
During check-ups, researchers collected information on four CVD risk factors:
overweight: body mass index (BMI) ≥ 25 kg/m2;
hypertension: systolic blood pressure ≥ 140 mm/Hg or diastolic ≥ 90 mm/Hg (self-report diagnosis or blood pressure medication);
diabetes: fasting glucose ≥ 120 mg/dL, nonfasting ≥ 200 mg/dL (self-report diagnosis or taking insulin); and
hypercholesterolemia: total cholesterol ≥ 200 mg/dL.
The new analysis from STAR assessed 714 individuals who were long-term members of Kaiser Permanente Northern California. They were recruited into the study at age 50 years and older and had no medical history that would affect cognition.
Investigators divided participants into groups according to age at which CVD risk factor data were measured: adolescents (12-20 years), young adults (21-34 years), and adults (35-56 years).
At baseline, the researchers collected information on education and income, and conducted cognitive assessments.
For cognition, verbal episodic memory, semantic memory, and executive function were measured using the Neuropsychological Assessment Scales. The mean age at cognitive assessment was 68 years.
After adjusting for age, gender, education, and years since risk factors were measured, results showed that both hypertension (pooled β = –0.18) and diabetes (pooled β = –0.69) in adolescence, young adulthood, or midlife were associated with worse later-life cognition.
Hypercholesterolemia among those who were adults during the MHC assessment was associated with worse later cognition (β = 0.22), but not among those who were adolescents or young adults.
Across age groups, having two or more CVD risk factors was linked to worse executive function (pooled β = –0.18) and verbal episodic memory (pooled β = –0.27) compared with not having CVD risk factors.
The association between semantic memory and CVD risk factors was not significant.
Unlike some recent research, the study did not find a connection between higher early life BMI and later dementia risk. That may be because of its small size or because not many children were overweight or obese in the 1960s, George said.
She noted that, to reduce these risk factors, heart and brain health promotion should target adolescents and younger adults.
“It’s important to have these interventions especially at a younger age. People generally think risk factors don’t appear until later in life, but in this population, risks are there early in life,” and as early as age 12 years, said George.
Although the researchers did not measure differences between males and females, “this is something we aim to do in the future,” she noted.
The investigators also plan to look at multiple time points and health checkups, and at cognitive decline over time, in future studies, she added.
Commenting on the findings for Medscape Medical News, Ralph L. Sacco, MD, professor and chair of neurology and executive director at the McKnight Brain Institute, Miller School of Medicine, University of Miami, Florida, said the study is in line with other research.
Multiple studies, including the Northern Manhattan Study that Sacco is involved with, have demonstrated the importance of the link between vascular risk factors and cognitive decline and dementia, he noted.
African Americans, as well as Hispanics, can be more vulnerable to cognitive decline because of vascular risk factors, particularly if these start in adolescence or midlife, added Sacco, who is also the immediate past president of the American Academy of Neurology.
“The earlier and the longer people have these risk factors, the more likely these risk factors can have an impact on cognitive health as people age,” he said. “We need to start lifestyle and behavior management to reduce vascular risks as early in life as possible.”
Also commenting for Medscape Medical News, Jeffery M. Vance, MD, PhD, professor of neurology, Hussman Institute for Human Genomics, which is also at the Miller School of Medicine, said the study supports current understanding of the causes of dementia.
Vance pointed to a number of previous studies that underline the vascular role in dementia.
A 2018 autopsy review of more than 1000 patients diagnosed with dementia showed that more than half the participants had a strong vascular component that contributed to their dementia. Studies of more than 7000 patients by the Alzheimer Disease Neuroimaging Initiative (ADNI) showed that vascular dysregulation of blood flow to brain cells is one of the earliest signs of the disease process that eventually leads to AD.
Vance also noted the importance of another study: the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER). Its results showed that intervening to reduce cardiovascular risk factors lowered the incidence of dementia.
The research helps illustrate the complexity of the process underlying dementia, but it primarily included participants of European ancestry, Vance said.
The current study “highlights the importance of these factors in African Americans, particularly, and strengthens the need to control these factors for both brain and heart health,” he added.
The study received funding from the National Institute on Aging. George and Vance have reported no relevant financial relationships. Sacco has reported receiving NIH funding for the Northern Manhattan Study.
Alzheimer’s Association International Conference (AAIC) 2020. Abstract #46253. Presented July 30, 2020.