Link Seen in Age at Retirement and Risk of Alzheimer’s

20130724-3

By John Gever, Deputy Managing Editor, MedPage Today

Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

20130724-4

 

  • Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
  • French retirees who had stopped working relatively late in life were less likely to develop Alzheimer’s disease.
  • Point out that the results are consistent with the growing body of evidence for the benefit of maintaining cognitive and social stimulation in seniors.

 

July 23, 2013, BOSTON — French retirees who had stopped working relatively late in life were less likely to develop Alzheimer’s disease, a researcher reported here.

Analysis of a French healthcare insurer’s records indicated that, for each year after age 60 at which a person retired, the risk of subsequently developing Alzheimer’s disease was lower by 3.2% (HR 0.968, 95% CI 0.962-0.973), said Carole Dufouil, PhD, of INSERM in Bordeaux, France.

After adjusting for certain other risk factors, individuals retiring at 65 were 14.6% less likely to develop Alzheimer’s disease than those retiring at 60, she said at a press briefing held prior to her formal presentation at the Alzheimer’s Association International Conference.

The results were “in line with the use-it-or-lose-it hypothesis,” she said, which holds that people who remain mentally active develop dementia at lower rates than those who don’t.

Data for the study came from an insurance provider for self-employed workers in France, mainly shopkeepers and craft workers, Dufouil explained. Records for some 430,000 pensioners as of December 2010 were analyzed, including 11,397 who were considered to have developed Alzheimer’s disease or related dementias after retirement.

The analysis excluded individuals whose records indicated a Parkinson’s disease diagnosis at any time and also those with apparent dementia at retirement.

Onset of Alzheimer’s disease was defined as a diagnostic code of ALD15 in the French healthcare system, which refers to “Alzheimer’s disease and related disorders,” or purchase of anti-dementia drugs such as memantine (Namenda) or acetylcholinesterase inhibitors.

Because they had such a large data set to work with, Dufouil and colleagues also conducted analyses to determine if the relationship between retirement age and Alzheimer’s risk differed among subgroups.

There were statistically significant differences in two groups — men versus women and craft workers versus shopkeepers — but all still showed a significant decrease in risk of at least 2% for each year beyond age 60 for retirement.

Stratification by age of birth or age at Alzheimer’s disease diagnosis also did not make a great difference in results, Dufouil said.

She added that sensitivity analyses in which some individuals were excluded — such as those with diagnoses within 5 or 10 years of retirement, those retiring after age 75, and those with relatively short periods of self-employment before retirement — also confirmed the topline results.

Dufouil noted several limitations to the study: The findings might not be applicable to other occupational types, the definition of new-onset dementia could be questioned, and the data lacked information on formal educational attainment and certain other important risk factors, she said.

Nevertheless, she said the results added to the growing body of evidence that “maintaining high levels of cognitive and social stimulation” is beneficial in seniors.

David Knopman, MD, of the Mayo Clinic in Rochester, Minn., who moderated the press briefing, cautioned that the findings may not entirely be an expression of “cognitive reserve,” the idea that individuals who exercise their brains regularly throughout life can retain normal cognitive function despite physical injuries and insults.

He noted that other factors that co-associate with mental activity — such as the ability to avoid other health risks, and the consequent lower risk of cardiovascular disease that can independently impair cognitive function — also have to be considered.

“All of these things bear on the ability of the brain to withstand the onslaught of something like Alzheimer’s disease,” he said. “[They] make the risk of Alzheimer’s disease a little more complex and these things can’t be ignored.”

 

The study had no commercial funding.

Dufouil had no disclosures. Knopman had relationships with Eli Lilly, TauRx, Janssen, Merck, Baxter, and Forest.


Primary source: Alzheimer’s Association International Conference
Source reference:
Dufouil C, et al “Older age at retirement is associated with decreased risk of dementia: Analysis of a healthcare insurance database of self-employed workers” AAIC 2013; Abstract O2-13-01.

 

20130724-1

THE NEW YORK TIMES
By HILLARY ROSNER
Published: July 23, 2013

 

For his master’s thesis research, Andrew Martin, an evolutionary biologist, studied the periodical cicada, an insect that lives underground and emerges once every 13 or 17 years. Traveling the United States from Georgia to Illinois to New York, Dr. Martin, now a professor at the University of Colorado, spent a summer up close with the cicadas. At each site, he would handle anywhere from 30 to 50 of them.

20130724-2

Graphic: Ellen Weinstein

The cicadas’ bodies were greasy to the touch, he recalled, and their abdomens were often coated with a whitish-green powder. It is a fungus that sterilizes and ultimately kills the insects.

A month into the research, the cicadas weren’t the only ones the green powder had afflicted. Whenever Dr. Martin touched it, his eyes itched and watered — symptoms that grew worse every time.

“When there were lots of the fungi, my eyes wanted to pop out of my head,” Dr. Martin recalled. “I wanted to scratch my eyes out.”

Dr. Martin had developed an allergy to his research subject, a fact that made finishing the project a grueling task. “I was always on something,” he said, referring to allergy medication, “but it was still bad.”

Becoming allergic to your research may sound like a classic avoidance strategy — like coming down with the flu (cough, cough) right before that big exam, or having to work (what a drag) on the weekend the in-laws come to visit. But it turns out to be a little-discussed but fairly common occupational hazard of science.

An estimated 15 to 20 percent of researchers who work with mice and rats, for instance, may eventually become allergic to the animals, said Dr. Karin A. Pacheco, an assistant professor of environmental and occupational health sciences at National Jewish Health in Denver. The real number could be even higher, because some people who become allergic may never report it, valuing their job above their health or comfort, Dr. Pacheco said.

Allergies are caused when our immune systems become overly sensitive to otherwise inoffensive substances. “The very first time you’re stung by a bee, you won’t be allergic,” said Dr. Pacheco. “You have to be exposed to the antigen and then develop an immune response to it.” Because scientific research often involves frequent and lengthy contact with a substance or creature, it’s something of a perfect vehicle for allergies.

Charlotte R. Hewins, a research specialist at the Holden Arboretum in Kirtland, Ohio, used to spend six months a year working with witch hazel plants, pollinating the flowers by hand.

Witch hazel, used as a garden shrub and medicinally as an astringent, grows tiny hairs on its leaves and twigs. When Dr. Hewins handled the plants, those hairs would come loose and float through the air.

Before long, she remembers, “I’d be getting rashes and hives on my hands and forearms. My eyes would be itchy and watery, and I’d be sneezing.”

For Burk Dehority , a microbiologist and professor emeritus at Ohio State University, the offending substance was formaldehyde. Dr. Dehority was studying protozoa that live in the stomachs of cattle.

“After using formaldehyde in liberal quantities for a number of years and getting splashed with it, I started to develop small blisters all over my hands,” Dr. Dehority said. He tried using rubber gloves, but that proved an incomplete solution. The chemical’s fumes were partially responsible for the allergy. So Dr. Dehority installed a fume hood — a similar device to the fan system that sits above a stove.

That seemed to make the work bearable, though the allergy persisted through 40 years of research. “I made a career out of studying protozoa,” he said. “It never occurred to me to switch.”

For Dr. Martin, too, abandoning the cicada project seems never to have entered his mind. “I was getting such cool data,” said Dr. Martin, who eventually earned his first publication in the journal Nature from the cicadas. “You become myopic about what you need to do.”

In fact, even a pre-existing allergy may not be enough to deter an obsessed scientist from a particular line of inquiry. Monica Raveret Richter, a behavioral ecologist at Skidmore College, developed a severe allergy to bees, wasps and mosquitoes as a child. Yet she has since spent much of her career studying the foraging behavior of wasps — aided by EpiPens and a supply of antihistamines. “If I get a lot of stings, I have issues,” she admitted. Still, she said, “I’ve learned to work around it.”