Another potential example for a DAG or two. Huang et al. (2025) found an association between hearing impairment and subsequent heart failure, which they attributed to a common cause of systemic vascular disorders. I don’t know anything about either topic, but it sounds plausible – more so than, e.g., hearing loss causing heart failure. They also found that whether people wore a hearing aid did not moderate this association – which again makes sense, though it was unclear what the authors expected:
“Of note, both the participants who used hearing aids and those with poor hearing status had a similarly significant increase in the risk of incident HF, suggesting that while hearing aids can improve auditory function, they may not address the underlying vascular issues that contribute to the risk of HF.”
I think it’s missing an “unsurprisingly”, but again don’t know the topic.
But then the mediation test comes along and suggests that the association between hearing loss and heart failure is mediated by psychological factors such as stress. Now how to get that in a DAG with the common cause model.
Here’s the relevant paragraph:
“Second, we found that the positive association between poor hearing status and incident HF was significantly mediated by psychological factors. Because hearing problems can lead to difficulties in speech comprehension and poor engagement in social activities, people with hearing impairment are more likely to experience social isolation, psychological distress, anxiety and depression than people without hearing impairment. These psychological factors may increase the activity of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, and enhance inflammation and oxidative stress, thereby accelerating atherosclerosis, increasing peripheral stress, and promoting the development of cardiac remodelling in the pre-HF period, thus significantly increasing the risk of HF.”
References
Huang, Y., Zhang, Y., Zhang, Y., Xiang, H., Ye, Z., Yang, S., Gan, X., Wu, Y., Zhang, Y., & Qin, X. (2025). Hearing impairment, psychological distress, and incident heart failure: A prospective cohort study. Heart, heartjnl-2024-325394.
