Fig. 4

The mean mid-peripheral CFZ width with standard error of the mean error bars for arterioles and venules in cognitively unimpaired (CU) low- and high-risk older adults. The periarteriole CFZ width is significantly greater than the perivenule CFZ width in both groups (p < 0.001) similar to that reported previously [22, 23]. The periarteriole CFZ width of the CU high-risk older adults is significantly greater than that of the CU low-risk older adults, p = 0.005, with a medium effect size (Cohen’s d) = 0.55. Similarly, the perivenule CFZ width of the CU high-risk older adults is also significantly greater than that of the CU low-risk older adults, p = 0.034, with a small effect size (Cohens’ d) = 0.42. *p < 0.05, **p < 0.01, ***p < 0.001