Perceived Hearing Symptoms Organize the Ear-Disease Comorbidity Network but Are Not a Causal Lever for Brain Health: A Triangulated Analysis

Background: Hearing loss is a potentially modifiable risk factor for brain health, but whether it acts as a causal lever remains unclear. Methods: We constructed an ear-disease comorbidity network from NHANES 2011-2020 (N=18,939, 16 nodes, 62 edges), performed bidirectional Mendelian randomization (MR) across 24 exposure-outcome pairs, and triangulated evidence with longitudinal data from CHARLS (N=17,101). Results: Subjective hearing symptoms (prevalence 6.1%) occupied hub positions in the comorbidity network, whereas objective hearing impairment (8.0%) was sparsely connected. All forward MR estimates were null after multiple-testing correction (IVW P>.05 for 9 of 9 pairs). Reverse MR showed one nominally significant association (cognition to objective hearing beta=-0.15, P=.013) that did not survive correction. Longitudinal analysis yielded HR=1.57 (P=.00004) for subjective hearing symptoms predicting incident depression. Conclusions: Perceived hearing symptoms organize the ear-disease comorbidity network but are not a causal lever for brain health. These findings support a "flag, not lever" framework: subjective hearing symptoms warrant clinical attention as markers of systemic multimorbidity rather than intervention targets for dementia prevention.