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More Risk Factors in Dementia: 40-45 year olds BEWARE

The number of people diagnosed with Alzheimer’s is expected to increase from 240,000 to 780,000 in the next 30 years. However the results from a U.S. study undertaken in 2005 may indicate that this number is on the low side because the study identifies obesity in mid-life (40 –45) as a significant risk factor in dementia. The study is one of two by Dr Rachel Whitmer, of the Kaiser Permanente Division of Research, et al., that identify a number of risk factors for dementia. The other culprits identified are smoking, hypertension, high cholesterol and diabetes.

The studies looked at the mid-life condition of the participants because the ratio of lean to fat mass changes with ageing, resulting in decreased body mass index and because the sub-clinical phase and initial onset of dementia affects appetite and causes weight loss, skewing the temporal association between weight and dementia.

The first study, ‘Midlife cardiovascular risk factors and risk of dementia in late life’ was published in Neurology in January. It was based on 8,845 participants, who underwent health evaluations from 1964 – 1973, when they were between the ages of 40 and 44. Diagnoses of dementia were ascertained by medical records from January 1994 to April 2003. 721 or 8.2% of the participants were identified as having dementia. Smoking during midlife was associated with a 26% increased dementia risk. Diabetes increased the risk by 46%, high cholesterol by 42% and high blood pressure by 24%.

The second study, ‘Obesity in middle age and future risk of dementia’, also by Whitmer et al., and published in June in BMJ, used 10,276 participants. As with the previous study, these men and women underwent detailed health evaluations from 1964 to 1973, when they were aged 40 – 45. Diagnosis of dementia was again undertaken between 1994 and April 2003. In this study, 713 participants (6.9%) were diagnosed with dementia. The obesity measures used were body mass index and tricep and subscapular skinfold thickness.

At mid life, 10% of the cohort were obese, 36% overweight, 53% normal weight and 1.3% underweight. Their conclusions were that compared with those with normal weight at mid life, obese people had a 74% greater risk of dementia, while those who were overweight had a 35% greater risk. Also, in sex specific models, body mass index was associated with dementia more strongly in women. Overweight women were 55% more likely to have dementia than women of normal weight, while overweight men had a non-significant 16% increase in risk compared with men of normal weight. Given the demographic structure of the Canadian population, with its increasing number of seniors in the next twenty years, this is cause for considerable concern.