Contrast Sensitivity Predicts 30-month Functional Brain Network Integrity in Cognitively Unimpaired Older Adults: the Brain Networks and Mobility Study (B-NET)

Background Visual contrast sensitivity (CS) is critical to many functions in older adults and is associated with brain network community structure, but the direction of the relationship between CS and the brain remains unclear. Methods We evaluated whether baseline binocular CS predicts 30-month functional brain network organization in 172 community-dwelling older adults (mean age 76.4±4.8 years, 56.4% female, 11.6% non-white/Hispanic) that underwent functional MRI (fMRI) at rest and during a motor imagery (MI) task. We constructed separate distance regression models for each of the 8 subnetworks covering the entire brain, while controlling for the baseline brain networks, sex, and the number of volumes removed during motion scrubbing from head motion in the scanner. Results Worse baseline CS predicted lower community structure integrity at 30-months in the visual network (VN, β=0.0115; p<0.0001), dorsal attention network (DAN, β=0.0075; p=0.0089), and default mode network both at rest (β=0.0173; p<0.0001) and during the MI task (DMN, β=0.0103; p=0.0002). No other networks showed significant associations. The DAN did not have a relationship with CS at baseline but was significant at 30-months. Similar findings were observed in models that additionally controlled for baseline MoCA and change in MoCA score over 30 months. Conclusions Poor CS may identify a subset of older adults at risk of future decrements in brain circuits important for vision, cognitive and mobility functions. Future studies should explore if improving CS increases functional brain health.