A group of researchers from Umea University in Sweden published two related studies in their attempt to explore a link between infection either chronic or acute with herpes simplex virus (HSV) and Alzheimers disease.
Such a linkage has been postulated for thirty years, according to the lead author of these studies, Dr. Hugo Lovheim, associate professor at the Department of Community Medicine and Rehabilitation, Geriatric Medicine, Umeå University, said. The theory was abandoned after the 1980s, but he did not feel that the tests done were adequate to relegate the idea to the science junkpile, yet. So he and his colleagues studied stored blood sera from 360 Alzheimer s Disease (AD) patients, and compared antibodies to HSV among them to samples from 360 matched, AD-free controls. That was the first study, and its results indicated that the presence of anti-HSV antibodies in the entire group provided no evidence of a link. But, when only considering those patients who had developed AD over 6.6 years after the serum specimen was taken, a significant association was indeed found: a two-fold higher incidence of the IgG type of antibodies (the long-lasting type) to HSV among AD patients.
They then went on to test samples from an ongoing study: the Betula Project, which was looking, prospectively, at aging, memory and dementia in Umea. They analyzed samples from 3,342 subjects, among whom 245 (7 percent) developed AD during the 11.3 year follow-up of the study. The results: 88 percent had long-lasting IgG-type HSV antibodies, without any significant link to developing AD. However, testing for the short-acting, acute-phase or IgM-type HSV antibodies likely indicating a re-activation of HSV infection revealed that 15 percent of AD patients had such, as compared to 7 percent of AD-free subjects, a significant two-fold increased risk.
"Our results clearly show that there is a link between infections of herpes simplex virus and the risk of developing Alzheimer's disease. This also means that we have new opportunities to develop treatment forms to stop the disease," said Dr.Lövheim, as quoted in the University s press release. "Something which makes this hypothesis very interesting is that now herpes infection can in principle be treated with antiviral agents. Therefore within a few years we hope to be able to start studies in which we will also try treating patients to prevent the development of Alzheimer's disease.
ACSH s Dr. Gil Ross warned those who want to leap into treatment: not so fast: The size of these studies quite small and the unimpressive albeit statistically significant results make me skeptical that HSV infection, whether chronic, acute or re-activated, is truly a causative factor in AD development. We in medicine and public health are truly frightened of the impending hoard of AD patients as our population ages, and we are bereft of early diagnostic abilities as well as anything like a therapy. So we must be cautious about letting desperation cloud our judgment here. Even if there were some link, just because an antiviral can often ameliorate HSV symptoms does not mean it would retard AD. Much, much more research is needed on this and other possible causative or risk factors.