March 25, 2009 (Prague, Czech Republic) — The world may be experiencing an epidemic of Alzheimer's disease (AD) that is not entirely attributable to an aging population, new research suggests.
Presented here at AD/PD 2009: 9th International Conference on Alzheimer's and Parkinson's Diseases, Murray Waldman, MD, from St. John's Rehabilitation Hospital, in Toronto, Ontario, found that while citations in the medical literature for femur fractures rose from 1706 to 3730 between 1996 and 2000, citations for AD and other dementias shot up from 1274 to 21 569 during the same time period.
Femur fractures make a good comparison for AD because both increase with age and treatment for both conditions has not changed significantly in the past 40 years, said Dr. Murray.
Little Mention Of AD Before 1960
Although AD is one of the most common diseases of the elderly, Dr. Waldman could find little mention of it before the 1960s. "I looked everywhere. I looked on 3 continents and in every medical library I could find, including the Library of Congress and the British Museum library," Dr. Waldman told Medscape Psychiatry.
"I also looked at psychiatric literature and at the pathology literature, but no matter where I looked, I couldn't find anything that indicated there was very much AD prior to the 1960s."
This lack of reference may indicate that AD did exist but nobody noticed it, "which I don't believe for a second, because of all diseases, Alzheimer's is one of the most difficult to miss," said Dr. Waldman. The only other plausible explanation, he said, is that it was less frequent then than it is now.
After 1960, the number of femur fractures rose in a linear fashion, reflecting the aging population. There were 1706 citations for these fractures from 1966 through 1970; 2077 from 1971 through 1975; 2356 from 1981 through 1985; 3235 from 1990 through 1995; and 3730 from 1996 through 2000.
In contrast, the number for AD and other dementias rose exponentially: 1274 citations from 1966 through 1970; 1733 from 1971 through 1975; 5465 from 1981 through 1985; 16 204 from 1991 through 1995; and 21 569 from 1996 through 2000.
This dramatic spike over 40 or so years, he said, cannot be accounted for by an aging population, "because what we were looking at was incidence, not prevalence."
Incidence Has Soared
Epidemiological data collected over a 25-year period shows the incidence of AD in the 1960s was 2% in people over the age of 85 years, whereas today, most experts accept that the incidence of AD in this population is 50%. It is 20% over the age of 75 years and 10% in individuals over the age of 65 years, he added.
"So the incidence seems to have soared enormously in this brief period."
The "exponential curve" pattern showing the rise in incidence of AD is similar to that of AIDS, said Dr. Waldman. Both patterns seem to fit the conditions of an epidemic. For example, the increased AD incidence began in Europe, moved to North America, then to Japan, China, and finally to India. India, he added, just started reporting AD cases in the past 5 years.
Dr. Waldman has his own theory of what might explain this spike in AD cases and wrote about it in his book Dying for a Hamburger (Toronto, ON: McClelland & Stewart, 2004). He's convinced that AD is due to prions, extraordinarily rare but extremely infectious agents. Prions apparently caused an outbreak of bovine spongiform encephalopathy in England over a decade ago.
He added he was disappointed that the AD/PD conference where he presented his work did not seem to feature research probing the causes of AD. "I didn't hear anything new," he said. "Nobody seems to be looking at what's causing this. No one seems to be asking the most fundamental question: Where does this disease come from?"
AD/PD 2009: 9th International Conference on Alzheimer's and Parkinson's Diseases: Abstract 90. Presented March 12-13, 2009
Medscape Medical News © 2009
Cite this: Pauline Anderson. AD/PD 2009: Are We Experiencing an Alzheimer's Epidemic? - Medscape - Mar 25, 2009.