I was reading about a recent large study on the effect of alcohol on longevity. It said in the past, the data used to show light drinking increased longevity. But that was because the “control” group was absolute non-drinkers. And some of these people didn’t drink because of their morbidity.
So, hopefully, any study that shows wearing hearing aids increases longevity has taken steps to throw out members of the control group who don’t wear hearing aids because of morbid conditions. The same consideration should apply to studies that claim wearing hearing aids helps reduce the incidence of dementia.
The recent large-scale study on alcoholic drinks on longevity used a control group of “occasional drinkers” rather than non-drinkers to help avoid the morbidity effect. Just smiling here, but are there enough “occasional hearing aid wearers” to form a similar control group for hearing aid longevity studies?
I suspect there are a fair amount of “occasional” hearing aid wearers out there. My father-in-law was one. Basically didn’t wear them until he was around family when he would wear them but he was frustrated that they didn’t help.
I’m not convinced there’s much value in these studies. They’re always going to be associational in nature as there’s no way we’re going to do a randomized study where we assign hearing aids to a portion of subjects who might need them. To me the value of hearing aids is that they either help the individual wearing them, or they help indirectly by helping individual’s family members. If neither of those is the case I doubt it’s worth wearing them because of some association with longevity or less dementia.
The “Lancet dementia commission” just published a new update (I posted this in the archieved “dementia” thread). They list hearing loss as the highest preventable risk factor for dementia. As you say, the problem with these studies are that they are all correlative- however there are quite a few of them and (naturally) all efforts are made to have fair controls. The suspicion is that such a risk is somehow linked with social isolation (another major risk factor). A mechanistic explanation could be that a lack of stimulation of certain brain areas sets a process in motion that ultimately leads to loss of cognitive function. Wild speculation ofc…