Cardiovascular risk factors tied to dementia risk: simple lifestyle changes that boost HDL cholesterol may have a substantial impact.
Data from three large population-based studies presented at the 9th International Conference on Alzheimer's Disease and Related Disorders support what has become a major focus in Alzheimer's disease research.
"Evidence has been building over the last 2 or 3 years that cardiovascular risk factors are also Alzheimer's disease risk factors. Consensus is building in the scientific community. This will be approached very vigorously, since these risk factors are very common," Dr. Hugh C. Hendrie, professor of psychiatry at Indiana University, Indianapolis, said at a press briefing during the meeting, presented by the Alzheimer's Association.
Elizabeth Devore, a third-year epidemiology doctoral student at Harvard Medical School, Boston, presented data from 4,081 female health professionals who had participated in the Women's Health Study and who had blood samples taken at baseline in 1992-1995. All were aged 65 years and older at follow-up, a mean of 5.8 years later. At that time, cognitive function was assessed by a telephone interview based on five tests measuring general function, verbal memory, and category fluency.
Of the 409 women with cognitive impairment (defined as a total cognitive score in the bottom 10%), 55 were in the top quintile for baseline HDL cholesterol, and 84 were in the lowest HDL quintile.
After adjustment for potential confounders--including age, educational level, body mass index (BMI), blood pressure, LDL cholesterol, triglycerides, and statin use--women in the top quintile for baseline HDL cholesterol were half as likely to have cognitive impairment as were those in the lowest HDL quintile.
"Put another way, this was the equivalent of saying that women in the highest versus the lowest quintiles for HDL were 2 years younger.... Simple lifestyle changes that increase HDL cholesterol may have a substantial health impact," Ms. Devore said.
A similar but nonsignificant trend was seen for LDL cholesterol; no trend was seen for triglycerides. The weaker relationship with LDL and triglycerides is consistent with data on cholesterol levels and cardiovascular risk in women, she noted.
A second study, from the Scandinavian Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) project, evaluated relationships between midlife body mass index and clustering of vascular risk factors with late-life development of dementia among 1,409 individuals.
At midlife, 35% of the subjects had normal/low BMIs of less than 25 kg/[m.sup.2], 49% were overweight (BMIs of 25-30 kg/[m.sup.2]), and 16% were obese (BMIs above 30 kg/[m.sup.2]). Cognitive status was evaluated an average of 21 years later, when the subjects were 65-80 years old. At that time, a total of 61 were diagnosed as having dementia, of whom 48 fulfilled the criteria for Alzheimer's disease, said Dr. Miia Kivipelto of the Karolinska Institute, Stockholm.
Dementia was diagnosed in 9.5% of the subjects with a midlife BMI above 30 kg/[m.sup.2], compared with 2.8% of those with low/normal BMIs. Similarly, Alzheimer's disease was present in 6.9% versus 2.4%.
Even after adjustment for age, sex, education, follow-up time, midlife systolic and diastolic blood pressures, cholesterol, smoking, apolipoprotein [epsilon]4 status, prior myocardial infarction, cardiovascular disease, and diabetes, the risk for late-life dementia was still nearly double (odds ratio 1.9) in those with BMIs of less than 25 kg/[m.sup.2], compared with those with BMIs greater than 30 kg/[m.sup.2], Dr. Kivipelto reported.
Both midlife systolic blood pressure and total cholesterol level were also independently associated with the development of late-life dementia. Subjects with systolic BP levels above 140 mm Hg were twice as likely as those below that level to have dementia, as were subjects with cholesterol levels above 6.5 mmol (253.5 mg/dL) compared with those below.
The three risk factors were additive, so that subjects who had all three were more than six times more likely to develop dementia than were those who had none, after adjustment for age, sex, education, and follow-up time, she said.
Lending support to the relationship between late-life dementia and high blood pressure was a third population-based study, this one in more than 5,000 individuals aged 65 years and older from Cache County, Utah (the Cache County Study).
Of 3,308 subjects initially without dementia who had been screened in 1995-1997 and survived to a second "wave" in 1998-2000, a total of 102 had developed Alzheimer's disease between the two evaluation periods, said Ara S. Khachaturian, Ph.D., a psychiatric epidemiologist with the Alzheimer's disease and aging consultancy group Khachaturian Associates, Potomac, Md.
Subjects taking any antihypertensive medication were 36% less likely than those not taking the drugs to develop Alzheimer's disease during the follow-up period, after adjustment for a list of factors including age, sex, education, apolipoprotein [epsilon]4 status, and a history of diabetes or heart disease. Alzheimer's risk was reduced significantly by use of [beta]-blockers (47%) and diuretics (39%). No significant relationship was seen with ACE inhibitors or calcium channel blockers.
When broken down further by subtypes of antihypertensive agents, the potassium-sparing diuretics had the most significant protective effect, with a 73% reduction in risk for Alzheimer's disease.
The findings, although significant, "must be regarded as preliminary," Dr. Khachaturian said.
BY MIRIAM E. TUCKER
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|Author:||Tucker, Miriam E.|
|Publication:||Internal Medicine News|
|Date:||Sep 1, 2004|
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