Food and Behaviour Research

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Obesity in middle age and future risk of dementia: a 27 year longitudinal population based study

Whitmer RA, Gunderson EP, Barrett-Connor, E, Quesenberry CPJr, Yaffe K. (2005) BMJ 330 1360 

Web URL: View this and related abstracts via PubMed here.

Abstract:

Objective: To evaluate any association between obesity in middle age, measured by body mass index and skinfold thickness, and risk of dementia later in life.

Design: Analysis of prospective data from a multiethnic population based cohort.

Setting: Kaiser Permanente Northern California Medical Group, a healthcare delivery organisation.

Participants: 10 276 men and women who underwent detailed health evaluations from 1964 to 1973 when they were aged 40-45 and who were still members of the health plan in 1994.

Main outcome measures: Diagnosis of dementia from January 1994 to April 2003. Time to diagnosis was analysed with Cox proportional hazard models adjusted for age, sex, race, education, smoking, alcohol use, marital status, diabetes, hypertension, hyperlipidaemia, stroke, and ischaemic heart disease.

Results: Dementia was diagnosed in 713 (6.9%) participants. Obese people (body mass index = 30) had a 74% increased risk of dementia (hazard ratio 1.74, 95% confidence interval 1.34 to 2.26), while overweight people (body mass index 25.0-29.9) had a 35% greater risk of dementia (1.35, 1.14 to 1.60) compared with those of normal weight (body mass index 18.6-24.9). Compared with those in the lowest fifth, men and women in the highest fifth of the distribution of subscapular or tricep skinfold thickness had a 72% and 59% greater risk of dementia, respectively (1.72, 1.36 to 2.18, and 1.59, 1.24 to 2.04).

Conclusions: Obesity in middle age increases the risk of future dementia independently of comorbid conditions.

FAB RESEARCH COMMENT:

This study found significantly increased risks for developing dementia in adults who were obese or overweight in mid-life (at 40-45 years of age), compared with normal-weight adults of the same age.

Importantly, these links between obesity, overweight and future dementia risks were independent of other physical health conditions linked with obesity, such as diabetes, hypertension, heart disease or stroke. 

This population-based study used data from a US medical health provider, which allowed researchers to follow up patients' health records for 20-30 years, and to control for numerous other factors already known or thought to affect dementia risk - including age, sex, race, education, smoking, alcohol use, and marital status.

While association studies can never provide definitive 'proof' of causal links, these data show that mid-life obesity is a strong predictor of dementia risk.

They are also consistent with the basic fact that body and brain health are strongly interconnected, for which there is already abundant evidence, although this is not yet reflected in public health policy or practice.