British researchers find positive, independent associations, especially in women with abdominal obesity

In older British patients, increased body weight and abdominal obesity increased the risks of developing dementia up to 15 years later, according to study results published in the International Journal of Epidemiology.In women age 50 years and older in particular, increased abdominal obesity was linked to a 39% increased risk of dementia compared with those with normal waist circumference, but the same effect was not seen in men.

For this study, Yixuan Ma, an MSc student at University College London, London, UK, and colleagues included 6,582 participants from the English Longitudinal Study of Ageing (ELSA). All were over 50 years old and dementia-free at baseline.

Normal weight BMI was defined as 18.5-24.9 mg/m2, and central obesity as a waist circumference (WC) of greater than 88 cm for women and greater than 102 cm for men. Dementia diagnoses were based on physician diagnosis, an overall score of greater than 3.38 on the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) and Hospital Episodes Statistics (HES) data.

During the 15-years follow-up, 6.9% of subjects developed dementia. Those who developed dementia were older at baseline than those who did not (71.8 versus 61.9 years, respectively).

Upon Cox proportional hazard regression analysis, researchers found that participants with a BMI ≥30 kg/m2 at baseline had a 35% greater risk of dementia (HR: 1.35; 95% CI: 1.09-1.61; P ˂ 0.05) compared with those who had a normal BMI. Even after controlling for hypertension and diabetes, the risk remained but was slightly lower (HR: 1.31; 95% CI: 1.03-1.59).

Ma and colleagues found no evidence of any association between BMI and apolipoprotein E-Ɛ4 (APOE-Ɛ4; P=0.141), gender (P=0.689), hypertension (P=0.823), or diabetes (P=0.941).

Upon sex-stratified analysis, they observed a 39% increased risk of dementia in women with abdominal obesity at baseline (HR: 1.39; 95% CI: 1.12-1.66; P ˂0.05) compared with those who did not have abdominal obesity. In men, there were no associations between abdominal obesity and dementia (HR: 0.84; 95% CI: 0.55-1.19; P=0.23).

Participants who were obese and had a high WC had a 1.28-fold increase in the risk of dementia compared with those with normal BMIs and WCs (95% CI: 1.03-1.53; P ˂0.05), translating to a 28% higher risk.

Finally, Ma and colleagues found an elevated risk of dementia in patients who were obese at baseline (HR: 1.34; 95% CI: 1.07-1.61) that was independent of gender, age, APOE- Ɛ4 level, education, physical activity, smoking, and marital status.

Study limitations include a length of follow-up that may not be sufficient to monitor the development of dementia, dementia identification was primarily based on physician diagnosis, and that the number of cases of diagnosed dementia was fewer than expected compared with the general population. Finally, the study was observational by design, and therefore, causality could not be established.

Steven T. DeKosky, MD, FACP, FANA, FAAN, of the McKnight Brain Institute, University of Florida College of Medicine, Gainesville, FL, and fellow of the American Academy of Neurology, reviewed these results.

“The study is carefully and well done. The study from which it is derived is also a valuable contribution to the literature both on its own and as an open dataset for other investigators to use for various analyses (including replication of the current study, if they wished). The fact that it is a longitudinal study rather than a cross sectional study is another strength,” he said.

Dr. DeKosky pointed out that the association between obesity and dementia is neither new nor surprising:

“There have been several previous studies looking at the relationship, and the general view has been that obesity in mid-life increases the risk of dementia and obesity in late life is not, and may even look ’protective.’ However, some of these studies have been cross-sectional, and some have been longitudinal, and not all data have been consistent. The co-factors of APOE genotype, age, sex, hypertension and diabetes are all significant factors to consider—and most of them have the potential effects of worsening cerebrovascular disease.”

Nevertheless, Dr. DeKosky noted, these results serve to reinforce healthful lifestyles for older patients who are at particular risk. All of the risk factors for cardiovascular disease are also risk factors for dementia and AD.

“Physicians are aware that in midlife, obesity, hypertension, diabetes or pre-diabetes, and sedentary behavior all increase risk for a variety of subsequent illnesses, including cardiac and cognitive. This is another strong reminder, from a longitudinal study, that urging overweight, diabetic, and pre-diabetic patients to exercise, lose weight and control other vascular risks,” Dr. DeKosky concluded.

  1. In older adults, large waist circumference and a high BMI were independently associated with an increased risk of dementia.
  2. In women over the age of 50 years, abdominal obesity significantly increased the risk of dementia; this effect was not seen in men of the same age.

E.C. Meszaros, Contributing Writer, BreakingMED™

This study was supported by the National Institute on Aging.

Ma reported no conflicts of interest.

 

Cat ID: 361

Topic ID: 82,361,282,404,730,361,192,51