TUESDAY, May 19, 2009 (HealthDay News) -- Losing weight rapidly late in life seems to signal a greater risk of experiencing some form of dementia, new research suggests.
For older adults, "basically, we saw that if you are thinner or are losing weight at a faster rate, then you are at a higher risk of developing dementia," said study author Tiffany F. Hughes, a postdoctoral fellow in the department of psychiatry at the University of Pittsburgh School of Medicine.
"This is in contrast to other studies that have shown higher BMI in middle age to increase risk of dementia," she acknowledged. "What is likely going on is that higher BMI in middle age is a true risk factor for dementia, while being thinner or losing weight more quickly in old age is a result of dementia that has not been detected yet."
Hughes, who conducted her research while a doctoral student at University of South Florida, published the findings in the May 19 issue of Neurology.
To assess the association, the study authors focused on a group of just over 1,800 Japanese Americans living in Washington state.
At the launch of the study in 1992, the participants were about 72 years old, on average, at which point all were free of dementia.
Over a period of eight years, Hughes and her colleagues tracked changes in body mass index (BMI), waist circumference and waist-to-hip ratio among the members of the study group, and then lined up those statistics against diagnoses of various forms of dementia, including Alzheimer's disease.
The team found that regardless of smoking history, exercise habits and gender, having a higher BMI late in life actually appeared to be associated with having a lower risk for developing Alzheimer's.
Looked at in reverse, the study authors observed that those participants who had a lower BMI at the study's launch actually faced a 79 percent greater risk for developing dementia.
In addition, participants of any weight who went on to lose pounds during the study period at a relatively fast rate had a three times higher risk for developing dementia than those who lost weight more slowly.
In fact, participants of any weight who went on to shed some pounds at a relatively slow pace over the course of the study period actually experienced a drop in their risk for developing either dementia or Alzheimer's.
However, the apparent connection between a drop in dementia risk and slow weight loss was especially pronounced among men and women who were either overweight or obese to begin with -- generally more so than among either normal or underweight participants who similarly lost weight. Specifically, the team observed that slow-paced weight loss among those with a BMI of 23 or above translated into an 82 percent drop in the risk for dementia.
The authors cautioned, however, that the findings could be skewed by the fact that seniors who began the study at a normal body weight naturally have fewer pounds to lose, and this could affect the pace at which any weight loss might have unfolded.
In addition, they noted that the study focused solely on Americans of Japanese ancestry, making it somewhat difficult to generalize the findings to other racial and ethnic groups. And they described the amount of time they spent tracking weight fluctuations as "relatively short," leaving open the possibility that different patterns of risk could be found if the same group were to be followed for a longer period.
Yet despite these caveats, Hughes and her colleagues concluded that having a relatively low BMI in late life appears to be a sign of underlying dementia-related disease -- particularly if a senior had been overweight or obese earlier in life.
"Being thin or rapid weight loss alone will not likely tell us who is going to get dementia," Hughes noted. "But along with other tests it may help doctors identify those who will, so treatment therapies can be started earlier."
For his part, Dr. Lon S. Schneider, a professor of psychiatry, neurology and gerontology at the University of Southern California, Los Angeles, said that when assessing the implications of this particular study "the devil is in the details."
"That said, it does seem that weight loss is a warning sign of something bad to happen," he noted. "Weight loss occurring over the age of 75 or 78 is a problem that predicts bad things in general. It's a major problem in the management of elderly people with illness. And almost always the explanation for unexplained weight loss at this age is a few years down the road. So yes, certainly it is the case that this is a development that could predict future cognitive impairment."
For additional information and resources on dementia, visit FamilyDoctor.org.