Stroke & Dementia Share Risk Factors

A growing challenge seen in all modern societies is taking care of a rapidly growing older population. A major cause of the disability seen in a large and growing number of older people is the result of strokes and/or dementia. In the United States alone there are about 800,000 strokes each year and there are now more than 5.5 million Americans with Alzheimer’s disease (AD) and another 1.5 million with vascular dementia. The good news is that the risk of older Americans developing dementia has been declining for at least the past two decades. Unfortunately, the number of older Americans is increasing much faster than this modest decline seen in the prevalence of dementia and stroke. As a result the number older Americans disabled by strokes and dementia will likely continue to increase thus placing an ever greater burden on the US healthcare system and on a growing number of families.¹

Unfortunately medical treatments of the brain damage seen in those who have suffered strokes and/or developed Alzheimer's disease and vascular dementias are largely ineffective leading a large number of older Americans to end up in long term care facilities. Food supplements such as omega-3 fatty acids have generally proven to also be largely ineffective at improving cognitive functioning in older adults who already have cognitive dysfunction.²

An Ounce of Prevention May Be Better than a Pound of Treatment

There is now growing evidence that cardiovascular risk factors seen in middle age are predictive of an increased risk of dementia in later life. For example, a cohort study of 15,744 black and white adults, examined in midlife for CVD risk factors to see if any of these risk factors had a significant impact on the risk of developing dementia over the next 25 years. The study was conducted on Atherosclerosis Risk in Communities (ARIC) participants who were evaluated in midlife in order to explore the associations between midlife vascular risk factors and 25-year incidence of dementia. The setting was ARIC field centers (Washington County, Maryland; Forsyth County, North Carolina; Jackson, Mississippi; and Minneapolis suburbs, Minnesota). The study participants (of whom 27.1% were black and 72.9% white) were initially aged 44 to 66 years. Vascular risk factors were measured at baseline including obesity, smoking, diabetes, prehypertension, hypertension, and hypercholesterolemia, as well as presence of the APOE ?4 genotype. After the baseline visit, participants had 4 additional in-person visits, for a total of 5 in-person visits, hospitalization surveillance, telephone calls, and repeated cognitive evaluations. Most recently, in 2011-2013, through the ARIC Neurocognitive Study (ARIC-NCS), participants underwent a detailed neurocognitive battery, informant interviews, and adjudicated review to define dementia cases. Additional cases were identified through the Telephone Interview for Cognitive Status–Modified or informant interview, for participants not attending the ARIC-NCS visit, or by an International Classification of Diseases, Ninth Revision dementia code during a hospitalization. Fully adjusted Cox proportional hazards regression was used to evaluate associations of baseline vascular and demographic risk factors with dementia.

In total, 1516 cases of dementia among the initial 15,744 participants. Black race (hazard ratio [HR], 1.36; 95% CI, 1.21-1.54), older age (HR, 8.06; 95% CI, 6.69-9.72 for participants aged 60-66 years), lower educational attainment (HR, 1.61; 95% CI, 1.28-2.03 for less than a high school education), and presence of the APOE ?4 genotype (HR, 1.98; 95% CI, 1.78-2.21) were all associated with an increased risk of dementia. In addition, midlife smoking (HR, 1.41; 95% CI, 1.23-1.61), diabetes (HR, 1.77; 95% CI, 1.53-2.04), prehypertension (HR, 1.31; 95% CI, 1.14-1.51), and hypertension (HR, 1.39; 95% CI, 1.22-1.59). The HR for dementia for diabetes was almost as high as that of the well-established APOE ?4 genotype, which has long known to markedly increase the risk of developing dementia.

It has long been known that heavy alcohol consumption damages the brain and contributes to the loss of brain function over time but there remains a debate about the potential benefit of moderate alcohol intake. A long-term study which followed 500+ middle-aged people (initial mean age 43 years) for 30 years in the UK to examine the impact of alcohol consumption on brain health. Over the 30-year follow-up period increasing alcohol intake was associated with greater hippocampal atrophy in a dose dependent fashion. While those consuming over 30 drinks a week were at the highest risk compared with abstainers (odds ratio 5.8, 95% confidence interval 1.8 to 18.6; P?0.001), even those drinking moderately (14-21 drinks/week) still had a better than 3-fold increased risk of right sided hippocampal atrophy (3.4, 1.4 to 8.1; P=0.007). Nor was there any sign of a protective effect of light drinking (1-6 drinks per week) over abstinence. Higher alcohol use was also associated with differences in corpus callosum microstructure and faster decline in lexical fluency. The study authors concluded: "Alcohol consumption, even at moderate levels, is associated with adverse brain outcomes including hippocampal atrophy. These results support the recent reduction in alcohol guidance in the UK and question the current limits recommended in the US."³

Bottom Line.

Further studies will be needed to evaluate potential mechanism by which a healthier diet and lifestyle can prevent stroke and/or dementia by reducing these cardiovascular risk factors in midlife. Until such definitive data become available it seems prudent to adopt a healthy diet low in added salt, alcohol, refined carbohydrates, and saturated fat and cholesterol and not smoke. Regular exercise and maintaining a healthy BMI are also likely to reduce the risk of stroke, Alzheimers disease, and vascular dementia.

By James J. Kenney, PhD, FACN

References:

1. https://www.scientificamerican.com/article/is-dementia-risk-falling
2. Andrieu, Guyonnet S, Coley N, et. al. Effect of long-term omega 3 polyunsaturated fatty acid supplementation fatty acid with or without multi-domain intervention on cognitive function in elderly adults with memory complaints(MAPT): a randomised, placebo-controlled trial. Lancet Neurology. 2017;16:377-89
3. Topiwala A. Allan CL, Valkanove V, et. al. Moderate alcohol consumption as risk factor for adverse brain outcomes and cognitive decline: longitudinal cohort study. Br Med J.2017; 357 doi: https://doi.org/10.1136/bmj.j2353