A Warning of Impending Alzheimer's?

Summarized by Robert W. Griffith, MD
May 4, 2005

Introduction

As we get older, we often have to struggle against increasing in weight. However, unintentional weight loss can occur, and it can often raise the suspicion of the presence of a malignant tumor somewhere in the body. But a new study shows that it may also be a warning sign of early Alzheimer's disease and vascular dementia. The report of this study, published in the Archives of Neurology, is summarized here.

What was done

The Honolulu-Asia Aging Study provided data on Japanese American men who had been weighed at intervals over a 34-year period (1965-1999) and who had been screened for dementia between 1991 and 1999.

There were 112 new cases of dementia diagnosed at the last screening for dementia (in 1999) among the 1,890 men in the study. Their body weight changes over the years were compared with those of the 1,778 participants without dementia.

What was found

The 1890 men in the study were aged between 77 and 98 at their last examination. At the start of study, and for the next 26 years, body weights were similar in the group of subjects who later developed dementia, and those who did not. It was only during the last 6 years that significant differences were seen.

After adjusting for differences in age, level of education, depression, and other factors that might affect either body weight or the likelihood of developing Alzheimer's, it was found that, during the last 6 years, the men who were eventually diagnosed with dementia had a significantly greater weight loss than the others.

Put another way, those men who later developed dementia lost an average of 0.36 kg/year (over 3/4 pound/year), compared with those without dementia, who lost 0.22 kg/year (1/2 pound/year). During the last 3 years alone, 30% of the men with dementia had lost at least 5 kg (11 pounds), compared with only 12% of the men without dementia.

The relationship between weight loss and later dementia was present for both Alzheimer's disease and vascular dementia.

What's the value of this finding?

The results of this analysis mean that doctors should consider early dementia when they see older patients with otherwise unexplained weight loss. (In the report it wasn't made clear if physical examinations were done looking for other causes of weight loss.) It's clear that weight loss occurred some time before Alzheimer's was diagnosed. And this raises questions:

• What's the likely mechanism of weight loss in these subjects?
• Does the weight loss cause, or accelerate the dementia?
• Can maintaining weight slow the progress of Alzheimer's?

It may be that early dementia interferes with the brain controls of appetite or body metabolism. But weight loss might contribute to, or speed up dementia, according to an eminent editorialist in the same journal.¹ And it makes sense to try to maintain body weight in such individuals - it may slow impending dementia, and it should certainly help reduce the risk of other problems, such as falls, delayed wound healing, or physical dependence on others.

Source

• A 32-year prospective study of change in body weight and incident dementia. R. Stewart, K. Masaki, Q-L. Xue,  et al., Arch Neurol, 2005, vol. 62, pp. 55--60

Footnotes
1. Weight Loss in the Elderly May Be a Sign of Impending Dementia. M. Grundman, Arch Neurol, 2005, vol. 62, pp. 20--22

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