The Metabolic Syndrome and the Risk of Alzheimer's

Summarized by Robert W. Griffith, MD
December 22, 2004

Introduction

Both Alzheimer's and vascular dementia are more likely to occur in people with high blood pressure or diabetes. So it's not surprising that investigators would want to find out if the metabolic syndrome, which includes both hypertension and raised blood sugar amongst its features, is itself a risk factor for cognitive decline (i.e. impaired mental processing). Their study results have been published in the Journal of the American Medical Association, and we summarize them here.

What was done

Participants in the study were enrolled from those taking part in the Health, Aging and Body Composition (ABC) study in Memphis, Tennessee and Pittsburgh, Pennsylvania. They were between 70 and 79 years old, and were considered well-functioning, with no difficulties with activities of daily living, no dementia, and cancer-free. The study lasted from 1997 to 2002.

The metabolic syndrome was defined as the presence of at least 3 of the following:

• Abdominal obesity - waist circumference greater than 102 cm (40 inches) in men, or 88 cm (35 inches) in women
• Blood triglyceride level 150 mg/dL or above (1.69 mmol/L or above)
• HDL-cholesterol 40 mg/dL (1.03 mmol/L) or below in men, or 50 mg/dL (1.29 mmol/L) or below in women.
• High blood pressure - 130/85 mm Hg or higher, or taking blood pressure medication
• High fasting glucose level - 110 mg/dL (6.1 mmol/L) or above

(If you want to see if you may have the metabolic syndrome, go to the first link below.)

Cognitive functioning was measured using the Teng Mini-Mental State Examination (3MS).¹ This was administered at baseline and at years 3 and 5.

Blood samples taken at baseline were examined for C-reactive protein (CRP) and interleukin 6 (IL-6) - two recognized markers for inflammation activity in the body.

Information was gathered on the participants' age, race, sex, years of education, current smoking, and alcohol use during the previous year.

What was found

There were over 2632 participants in the study. Their average age was 74, 52% were women, 40% were black, and 25% had high values for CRP and/or IL-6. There were 1016 people (39%) who had the metabolic syndrome, and 1616 people (61%) who didn't. Those with the syndrome were more likely to be women, white, and smokers. They were also more likely to have high markers for the presence of inflammation.

Compared with those without the metabolic syndrome, those with the syndrome were more likely to have cognitive impairment - 26% vs. 21%. Put another way, people with the metabolic syndrome are 1.2 times as likely to develop cognitive impairment.

The possible role of inflammation was examined in more depth. It was found that those with the metabolic syndrome and high levels of inflammation markers (348 subjects) were 1.66 times as likely to develop cognitive impairment; whereas those with the syndrome and low inflammation markers (668 subjects) had no such increased risk.

What this means

This study shows that well-functioning older people with the metabolic syndrome are at an increased risk of declining mental functioning. This linkage remains even after adjustments for age, lifestyle, etc have been made. And the risk is increased in those metabolic syndrome subjects who have evidence of inflammation in the body.

Two previous studies have found similar results for the link between the metabolic syndrome and cognitive impairment, but this is the first time that inflammatory markers have been given a role in the process. These markers probably serve as an indication of an active pathological process; but do the features of the metabolic syndrome come first, or the inflammatory changes? The answer to this question will provide the direction for preventive treatment of mental decline. There's a supporting clue - both statins, which are anti-inflammatory, and NSAIDS have been reported to reduce the risk of Alzheimer's. Clearly this is an important area for further research. In the meantime, there are plenty of good reasons for us to avoid or reverse just about all the features of the metabolic syndrome, if we can, by appropriate lifestyle changes. You know these by now: no smoking, a healthy diet, and plenty of exercise!

Source

• The metabolic syndrome, inflammation, and risk of cognitive decline. K. Jaffe, A. Kanaya, K. Lindquist,  et al., JAMA, 2004, vol. 292, pp. 2237--2242

Footnotes
1. The 100-point 3MS is more sensitive than the traditional 30-point MMSE. Cognitive impairment is defined as a change of 5 or more points on the 3MS.

Related Links
Tool: Do You Have the Metabolic Syndrome (Syndrome X)?
Statins to Stop Dementia?
Do You Know Your CRP?

Please take a moment to give us your comments. For questions about Health matters you may check our "Questions & Answers" Portal and Service.