< Back to Menu

Obesity at age 50 seems to increase risk of later dementia and Alzheimer Disease
(February 2006)

In recent years, there has been huge interest in the health consequences of overweight and obesity. Three recent observations suggest that:

-  Moderate to severe obesity, a BMI of 35 or more increases death rates to a moderate degree for adults under age 70, but only a little for those over age 70. (BMI = weight in kilometers divided by the height in meters squared; a BMI of 35 represents 40 percent overweight when compared to a normal BMI of less than 25 - CLICK HERE for a table to calculate your own BMI)

- The high blood pressure that often accompanies obesity appears to be a critical factor in increased deaths.

- The bigger problem with mild obesity (BMI 30 to 34.5) and more severe obesity (BMI 35 and over) is an increase in chronic disability.

A new study in the October 2005 issue of the Archives of Neurology suggests that obesity at age 50 doubles the risk of dementia some 20 years later. Scandinavian investigators followed 1,419 men and women who, at followup, averaged about 71 years of age. At that time, 61 of the participants had evidence of dementia, about four-fifths of whom were given a diagnosis of Alzheimer's, the rest being vascular dementia due, in large part, to a reduced blood supply to the brain.

Anyone with a BMI at enrollment greater than 30 was classified as obese. No attempt was made to separate mild from more severe obesity. At the end of the followup period, 2 percent of those with normal weight (BMI less than 25) had developed diabetes as had 6 percent of those who were overweight (BMI 25 to 29.9) and 19 percent of those classified as obese (BMI 30 and over).

The risk of dementia for those obese at enrollment was more than doubled. Those who were overweight (but not obese) at enrollment had no increased risk of dementia.

The investigators then analyzed enrollment values of three potential specific risk factors for dementia - a high cholesterol (greater than 250 milligrams, quite high), a high systolic blood pressure (greater than 140 millimeters of mercury), and obesity (BMI over 30) and found that any combination of two of the three risk factors increased risk of dementia by threefold. If an individual had all three risk factors, the likelihood of developing dementia increased sixfold.

The authors conclude that mid-life obesity is a significant risk factor for later dementia and that, for obese persons, weight reduction should be considered as a possible way of reducing the risk for dementia later in life.

Commentary: This is a very interesting article. The authors cite three other studies -one is in agreement; one agreed, but only for vascular dementia, not Alzheimer's; and one found no association with mid-life obesity. Still, there are multiple studies that find risk factors for heart disease, particularly high blood pressure and high cholesterol level, are also risk factors for both vascular dementia and Alzheimer's. Of course, we still do not know the cause of Alzheimer's or which of the many risk factors postulated are really important.

There are several points to note about this study:

- The number of dementia cases in each of the three groups (normal weight, overweight, obese) was small ranging from 14 to 26. That mandates caution in interpretation.

- With the small number, it was impossible to separate obesity into mild, moderate, and severe. That will have to be done before this issue is settled.

- There is a real flaw. At the followup, blood cholesterol levels were determined as was blood pressure, but we are not told about the results, so we do not know whether the patients who developed dementia continued to have high cholesterol levels and blood pressure during followup and whether high cholesterol and blood pressure at followup were associated with higher dementia frequency. It is inexplicable that the information was not provided.

- Although obesity at midlife was correlated with dementia likelihood, at followup, the average BMI was the same for those who had developed dementia and those who had not. That suggests that much of the increased risk among obese persons, indeed perhaps all the risk, could be related not to the weight itself, but rather obesity-related high blood pressure, high cholesterol level, and diabetes. This would be consistent with the growing evidence that weight by itself is less important than the specific abnormalities it creates. That, in turn, suggests that overweight and obese persons should regularly monitor their cholesterol levels, blood pressure, and blood glucose (sugar) levels and do whatever is needed to control them. By the same token, as suggested by one of the tables in the present paper, an obese person with normal blood sugar, normal blood pressure, and normal cholesterol level may not be at increased risk for dementia (or for increased risk of death).  

In this study, the average age at followup was 71 years. The results might be more dramatic if this population is followed for an additional ten years, during which time, the number of Alzheimer's cases in all weight groups should increase substantially.

Kivipelto, M., et al. Obesity and vascular risk factors at midlife and risk of dementia and Alzheimer Disease. Archives of Neurology. Vol 62 (October) Pgs 1556-1560. 2005.

Another reason for weight control and for those overweight controlling overweight-related risk factors.

Supported by