They also highlight HSV as a particularly likely cause of these dangerous infections.
The editorial — not a new study, but essentially an open letter to the medical community based on previous (inconclusive) research — was covered in fairly alarmist fashion by the Telegraph. Many outlets, including TIME and several men’s websites, followed suit. But buried near the end of the Telegraph’s own coverage is a very telling quote:
“This is a minority view in Alzheimer research,” John Hardy, a professor of neuroscience at University College London, told the Telegraph. “There had been no convincing proof of infections causing Alzheimer disease. We need always to keep an open mind but this editorial does not reflect what most researchers think about Alzheimer disease.”
Here’s the problem with the research being brought to our attention: It’s all correlative. That means that a handful of studies have shown that older folks with active HSV infections (the virus lies dormant most of the time) are more likely to be diagnosed with Alzheimer’s than those without. But no one has shown why this would happen, or given any evidence that it’s the HSV causing the Alzheimer’s. If they had done that, we’d say there was evidence of a causative relationship — signs pointing to one of the diseases causing the other.
For all we know, the correlative relationship is pure coincidence — some estimate that 80 percent of the U.S. population has HSV-1, and that’s a big chunk. There could be other, as-yet-uncovered risk factors that these individuals also had in common.
And the relationship could actually work in the other direction, too. It’s possible that something about Alzheimer’s — the disease itself, or some insidious internal process that makes it more likely to develop — makes the many, many people who also happen to have HSV more likely to have active symptoms of the virus.
In response to a pair of these studies in 2014, Cleveland Clinic Alzheimer’s specialist Jagan Pillai emphasized that the connection between the virus and the brain ailment is still murky.
“The studies show that for some as-yet unclear reason, immune changes related to herpes simplex 1 appear to be more common in older individuals (meaning older than age 60) with Alzheimer’s,” he said in a Q&A posted by Cleveland Clinic. “The research does not say, nor does it tell us, if the herpes simplex 1 virus caused Alzheimer’s. It could be that immune changes related to Alzheimer’s disease simply cause more reactivations of the virus. So the bottom line is right now, there is no reason to be alarmed. Having the herpes simplex 1 virus does not mean that it’s certain you will go on to develop Alzheimer’s disease.”
He also pointed out that the studies rely on clinical diagnosis of Alzheimer’s — as opposed to posthumous examination of the brain — and that these diagnoses are accurate only about 70 percent of the time. It’s quite possible that the apparent significance of the correlation between HSV and Alzheimer’s would drop away if those inevitable false diagnoses were removed from the data set.
In an email to The Post, Hardy agreed that, to date, the evidence was “all correlative.”
It’s not surprising that the Telegraph chose to lead with a more alarming interpretation of the editorial — or that other outlets used them as a source without bothering to mention any arguments against the editorial’s conclusions. Even though most people have herpes (yes, most people — even you) the virus’s increasing sexual transmission turns it into an instant punchline. Saying that “there’s a possibility that HSV-1 and Alzheimer’s might be connected somehow, but we aren’t really sure if that’s the case or what it would mean” just doesn’t hit the same sweet spot as this:
There’s nothing wrong with trying to direct more research at this proposed link. But implicating HSV — a disease that already gets way more stigma than it is due — as the dastardly culprit behind a devastating disease is not based on sound science.