The researchers suggest studying risk factors for mild cognitive impairment separately in men and women. (Enrique Castro-Mendivil/Reuters)

Men may be at higher risk of mild memory loss as they age than women, according to a new study.

The study in Tuesday's issue of Neurology looked at mild cognitive impairment — showing symptoms of memory problems that are not severe enough to be considered dementia.

Dr. R.O. Roberts of the Mayo Clinic in Rochester, Minn. and his co-authors followed a group of 1,450 people aged 70 to 89 for an average of three years. None of the participants had dementia when the study began.

The people in Olmsted County, Minn. had memory tests every 15 months during the study, with nearly half having four assessments.

The number of new cases of dementia per year was higher in men, at 72 per 1,000 people compared with 57 per 1,000 people in women, the researchers found.

Those who were not married or had less education were also more likely to develop memory loss.

"Our study suggests that risk factors for mild cognitive impairment should be studied separately in men and women," said Roberts.

Brain improvements

In general, men tolerate deficits less well than women do, Dr. Kenneth Rockwood of the geriatric medicine research unit at Dalhousie University in Halifax said in a journal editorial accompanying the study.

Intriguingly, Rockwood noted, the study's authors also reported that about one-third of of people initially diagnosed with mild cognitive impairment were subsequently diagnosed at least once with no cognitive impairment — a finding that's also been seen in previous studies.

Of the 284 people who developed mild cognitive impairment, 148 had a follow-up. Of that group, 98 or 66 per cent remained impaired and 50 or almost 34 per cent "reverted" to normal, the researchers said.

"Improvement compared with progression is an important challenge to the conventional view that MCI criteria imply a risk of dementia, but it might represent more," Rockwood said. It could be a reflection of how the brain might struggle with damage and repair as it ages.

Both Rockwood and the researchers called for more investigation on risk factors for mild cognitive impairment separately in men and women to help understand these differences.

Since the participants were mainly of European ancestry, the results may not apply to other ethnic groups, the study's authors said.

The study was funded by the National Institutes of Health, Robert Wood Johnson Foundation and the Robert H. and Clarice Smith and Abigail van Buren Alzheimer's Disease Research Program.