Just days into 2004, are you already struggling with those New Year's resolutions to eat right, exercise and shed excess pounds? Here's added incentive to stick with the program. It turns out that the healthy measures most of us vow to take every New Year's could not only make us look better in bathing suits but also lower our risk of Alzheimer's disease.
For generations, Alzheimer's has seemed as unpredictable as a game of chance--either you win or lose at dementia roulette. But that picture is starting to change. Scientists have long known that proper diet, exercise and weight control can help lower the risk of heart disease, strokes and vascular dementia. Now they're recognizing that the same healthy-lifestyle factors may also lower the risk of Alzheimer's. In short, what's good for the heart is good for the brain. "Over the last three years, the single most significant trend in research is the evidence that risk factors for heart disease track with those for Alzheimer's," says Bill Thies, vice president of medical and scientific affairs of the Alzheimer's Association, a nonprofit group in Chicago.
The vascular hypothesis, as the idea has come to be known, got its tentative start in the 1980s at the medical examiner's office in Lexington, Kentucky. Neuropathologist Larry Sparks, who was then the chief bio- medical consultant, was studying the brains of people who had died in a variety of accidents. None of the victims had overt signs of dementia. But Sparks noticed that many of their brains bore the same telltale amyloid plaques and neurofibrillary tangles that characterize the brains of Alzheimer's patients. As the number of cases grew, he noticed that plaques and tangles were three times more common in the brains of people with heart disease. "If they were resilient enough not to succumb to heart trouble in their 60s, they might be staring down the loaded barrel of dementia in their 80s," says Sparks, now with the Sun Health Research Institute in Arizona. Many scientists were skeptical.
Then results started coming in from long-term epidemiological studies. In 1996 Dr. Ingmar Skoog, a psychiatrist at Goteborg University in Sweden, published a study in The Lancet showing a correlation between high blood pressure at the age of 70 and a tendency to develop Alzheimer's 15 years later. Was hypertension years earlier setting people up for Alzheimer's in their old age?
Other studies suggested it was. In 2000 the Honolulu-Asia Aging Study reported that middle-aged Japanese-American men with diastolic blood pressure over 90 (the second of the two blood-pressure readings is diastolic) ran five times greater risk of dementia 20 to 25 years later than those with diastolic pressure in the 80-to-89 range. If the men treated their high blood pressure, however, risk of later Alzheimer's fell. The Honolulu findings were particularly powerful because the researchers were able to examine the brains of participants at death. "The higher their midlife blood pressure, the more plaques and tangles they had on autopsy," says Lenore Launer, chief of neuroepidemiology at the U.S. National Institute on Aging and one of the investigators.
In the past three years, still more cardiac risk factors have been implicated in Alzheimer's disease--smoking, atherosclerosis, high cholesterol and excessive levels of a substance in the blood called homocysteine. Moderate smoking, for example, doubled or tripled Alzheimer's risk in two studies. Obesity poses a risk, too. In the Goteborg study in Sweden, every one-point increase in body-mass index at the age of 70 increased the risk of Alzheimer's 15 years later by 36 percent. Diabetes, which is also associated with excess weight, doubled the risk of Alzheimer's in two other large surveys.
Want to lower your chances of dementia? A heart-healthy diet is a good place to start. Last summer Martha Clare Morris of the Rush Institute for Healthy Aging in Chicago published an epidemiological study showing that senior citizens who ate fish at least once a week had 60 percent less risk of getting Alzheimer's four years later. It's too early to say why, but Morris noted a correlation between intake of DHA--one of the omega-3 fatty acids in fish--and reductions in Alzheimer's. "DHA is the primary lipid in the brain," she noted. In other surveys, she's found that those who eat the greatest quantities of foods containing vitamin E--such as vegetable oils, wheat germ, whole grains, sunflower seeds and collard greens--reduce their risk as much as 70 percent. On the opposite side of the ledger, saturated fat and trans fats appear to increase the incidence of Alzheimer's.
At this stage, none of these results are conclusive. The evidence comes mainly from epidemiological studies, which find associations but don't establish cause and effect. The vascular hypothesis won't be secure until research firmly links cardiovascular risk factors to mechanisms underlying the development of Alzheimer's. Such evidence is starting to emerge. For example, scientists have shown that high cholesterol in rabbits, mice and guinea pigs leads to increased formation of amyloid plaques in the animals' brains. But the evidence is still preliminary.
Even if the research holds up, there are no guarantees that any individual will be able to avoid the devastating illness. The rare early-onset Alzheimer's that strikes people in their 40s and 50s is heavily controlled by genetics. The more common late-onset form seems more amenable to reduction, but genes still play a role. In the end, however, it can't hurt to adopt more heart-healthy behaviors.