A recent study by Natacha Lorius et al. explored whether a connection exists between vascular disease or vascular risk factors, and cognitive decline. Vascular diseases are illnesses that affect blood vessels, and cognition is the mental process by which knowledge is gained through thought, experience, and the senses.(AD) The researchers hypothesized that vascular disease, as well as vascular disease risk factors, would correlate with cognitive decline both cross‐sectionally and longitudinally across the AD spectrum. To answer this question, a between‐subjects experimental design was employed and patients with AD, mild cognitive impairment, and normal control subjects were recruited for the study. The subjects underwent cognitive skills assessment, brain magnetic resonance imaging, and clinical evaluation for the course of three years. The selected participants did not start out with much stress in their vascular system. Stress in subjects’ vascular system was evaluated so as to ensure a difference in global cognition and memory decay between their initial and final visit.
[pullquote align=”right” cite=”” link=”” color=”” class=”” size=”10″]The researchers hypothesized that vascular disease, as well as vascular disease risk factors, would correlate with cognitive decline both cross‐sectionally and longitudinally across the AD spectrum.[/pullquote]
Data analysis employed statistical models such as Cox proportional hazards, longitudinal mixed effects, and general linear models. The study found strong support to suggest that higher numbers for white matter hyperintensity and homocysteine values indicated problems with processing speed and that a larger result in vascular index was linked with issues in memory. The study also found that rate of global cognitive impairment and memory decay was associated with greater total cholesterol levels and increased apolipoprotein E ε4 (APOE4) alleles. The aforementioned findings were important in understanding that the increase in vascular disease or risk factors and cognitive impairment are closely related in those who have Alzheimer’s disease.
In the Cross‐sectional Analyses section of their publication, Lorius and colleagues explained that a higher number for homocysteine relates to a smaller number for Digit Symbol, a higher processing speed impairment. The results showed that white matter hyperintensity and Digit Symbol score are negatively correlated. Performance on memory tasks was evaluated by a total score measured from an instrument called the Rey Auditory Verbal Learning Test (RAVLT). This tool was used to explain the relationship between vascular index and RAVLT Total Learning, or higher memory impairment. The results indicate a negative correlation between vascular index and RAVLT Total Learning. The authors evaluated higher global cognitive impairment through a tool called the Alzheimer Disease Assessment Scale Cognitive Subscale (ADAS‐Cog score) and found a positive correlation between cognitive impairment and factors such as the number of apolipoprotein E ε4 alleles and serum total cholesterol. Lorius and colleagues report that the initial ADAS‐Cog score was dependent on time. As time went by, a higher initial ADAS‐Cog score related to a larger rate of increase in ADAS‐Cog score. There is a positive correlation between initial ADAS‐Cog score and later ADAS‐Cog score.
The authors’ cross‐sectional and longitudinal analysis demonstrated that there is a substantial connection between increased vascular disease or risk factors and cognitive impairment with those who have Alzheimer’s disease and did not initially have substantial vascular stress. The cross‐sectional analyses showed that there are different types of vascular disease and risk factors that affect cognitive impairment, but the status of apolipoprotein E ε4 carrier appeared to be the primary marker for cognitive disability in a diagnostic group that was further impaired. In the cross‐sectional analysis, a strong correlation was observed between higher white matter hyperintensity volume, higher amounts of homocysteine, and lower processing rate; higher score for vascular index and more problems in memory; and the presence of apolipoprotein E ε4 and more global cognitive dysfunction. Taking into account lipid decrease caused by drugs, a larger initial level of total cholesterol was connected with more memory and global cognitive deficiencies. This supports previous findings that show a link between hypercholesterolemia and decline in global cognition, growth of disease in mild cognitive impairment, and Alzheimer’s disease dementia. Systolic blood pressure and body mass index were not related to cognitive measures. This research supports previous findings that indicate that there is no association between higher late‐life body mass index and cognitive deterioration, whereas higher mid‐life body mass index has been shown to be beneficial in reducing the risk of Alzheimer’s disease dementia. All in all, Lorius and colleagues’ research provides strong support to suggest that increased vascular disease and vascular risk factors correlates strongly with cognitive impairment in people who have Alzheimer’s disease and are not affected by cerebrovascular disease.
Lorius, N., Locascio, J. J., Rentz, D. M., Johnson, K. A., Sperling, R. A., Viswanathan, A., & Marshall, G. A. (2015). Vascular disease and risk factors are associated with cognitive decline in the Alzheimer’s disease spectrum. Alzheimer Disease and Associated Disorders, 29(1), 18–25.