Frontal white matter hyperintensity burden predicts cognitive response to N-acetylcysteine and exercise in vascular mild cognitive impairment.

Vascular mild cognitive impairment (vaMCI) is a prodromal stage of dementia defined by cognitive deficits due to cerebrovascular disease. Increased white matter hyperintensity (WMH) volume has been associated with reduced executive function (EF). We explored whether lower baseline frontal and global WMH volume predicted an improvement in EF in vaMCI participants treated with N-acetylcysteine (NAC) and exercise as compared to placebo and exercise. Fifty-eight individuals with vaMCI received exercise therapy and were randomized to NAC or placebo. EF was assessed using the Trail Making Test Part B (TMT-B), Digit Symbol-Coding Test (DSCT), and a test of phonemic fluency, at baseline, 3 months, and 6 months. WMH volumes were measured from baseline magnetic resonance imaging scans. Linear mixed models were used. All participants improved on TMT-B (β = -0.185, SE = 0.046, p < 0.001) and phonemic fluency (β = 4.440, SE = 0.911, p < 0.001) over 6 months. A significant three-way interaction between baseline frontal WMH volume, treatment group, and timepoint predicted TMT-B performance at 3 months (β = 0.160, SE = 0.076, p = 0.039), but not at 6 months. No significant interactions were found for DSCT or phonemic fluency. Global WMH did not predict treatment response. Participants demonstrated improvement in EF regardless of treatment group and WMH volume. Lower frontal WMH volume predicted a greater improvement in TMT-B performance at 3 months in those treated with NAC versus placebo. These findings underscore the importance of considering participant heterogeneity in trials for vaMCI.