Editor—Whitmer et al reported a prospective study showing that obesity in middle age was associated with increased risk of future dementia.1 However, little information was given on the types of dementia. This is important especially in Alzheimer's disease, in which vascular risk factors might contribute to its development.2 We have investigated the relation between Alzheimer's disease and obesity throughout adult life in a small case-control study.
We recruited 25 patients with probable Alzheimer's disease from the Launceston Memory Disorders Clinic, Tasmania, and 50 controls from the local community. Patients were living at home and were physically well, with no important medical problems. Current height, weight, and waist circumference were measured. In addition, we asked participants to recall their weight at the age of 20-25 and 40-45. Self reported weight has been shown to be highly correlated with direct measurement in cognitively healthy people and those with mild to moderate dementia.3,4
The mean age of patients with Alzheimer's disease and controls was 74.9 (range 57-88) and 72.1 (65-94), respectively. The mean mini-mental state examination score was 19.0 (4-26) for patients with Alzheimer's disease and 29.6 (28-30) for controls. Most patients had mild to moderate disease (80% with scores greater than 14). The table shows that at midlife, patients with Alzheimer's disease had higher body mass index (BMI) by 2.8 kg/m2 or 12% than controls. At late life, BMI was not significantly different, but the waist circumference in patients with Alzheimer's disease was higher than in controls by 6.1 cm, or 7%.
Table 1.
Means (standard errors) and logistic regression odds ratios (per standard deviation) for BMI and waist circumference, adjusted for age, sex, years of education, cigarette smoking, and alcohol consumption
| Variable (SD) | Patients with Alzheimer's disease | Controls | Odds ratio (95% CI) |
|---|---|---|---|
| BMI at age 25 (3.5 kg/m2) | 23.5 (0.9) | 22.8 (0.5) | 1.16 (0.64 to 2.10) |
| BMI at age 45 (3.9 kg/m2) | 27.1 (0.9) | 24.3 (0.6)* | 2.06 (1.01 to 4.21) |
| BMI at age 65+ (4.1 kg/m2) | 26.5 (1.0) | 25.5 (0.6) | 1.24 (0.68 to 2.26) |
| Waist circumference (11 cm) | 88.4 (3.3) | 82.3 (3.2)* | 2.05 (0.99 to 4.26) |
P<0.05, calculated by using general linear model analysis.
BMI=body mass index
Our study supports the conclusion of Whitmer et al that midlife obesity increases the risk of future dementia, in this case Alzheimer's disease. In addition, abdominal obesity, which is highly associated with insulin resistance and cardiovascular diseases, might also be a risk factor for Alzheimer's disease.
Competing interests: None declared.
References
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