Reducing the risk of Alzheimer's

Reducing the risk of Alzheimer's

Controlling one’s drinking and smoking habits can delay the onset of Alzheimer’s disease.

Keeping it at bay: With proper care, the prevalence of Alzheimer’s can be brought down.

Alzheimer’s disease is a progressive, age-associated neurological disorder that initially affects the ability to recall recent events, but ultimately leads to an inability to function independently. As countries develop economically and the lifespan and the average age of its citizens increase, so does the number of individuals affected with Alzheimer’s disease. For societies with high proportions of older citizens, the epidemic of Alzheimer’s disease is a looming and major concern. Some of the most troublesome symptoms of this disease are not just those that affect memory and other mental abilities. Depression, paranoia and agitation, impaired balance, frequent falls and incontinence are features of the later stages of the disease and these greatly impact on the quality of life of the patients and on their family members. Modifiable factors

Although age is the single biggest risk factor for Alzheimer’s disease, genetic factors, which are not modifiable, and other factors, which are modifiable, are known to be strongly associated with the disease. The prevalence of a disease, i.e., the number of people that are affected by that disease at any given point in time, is a measure of the burden posed to society by that disease. After the age of 65, the prevalence of Alzheimer’s disease doubles about every five years. If we could delay the onset of Alzheimer’s by five years, we could reduce its prevalence almost by half. As such, an important public health goal should be to identify and control all modifiable risk factors for Alzheimer’s disease, so as to delay the age of onset of the disease and dramatically reduce its prevalence.

At Mt. Sinai Medical Center, Miami Beach, Florida, my colleagues and I investigated how heavy smoking, which was defined as smoking two or more packs of cigarettes per day, and heavy drinking, which was defined as consuming more than two drinks a day, affected the age of onset of symptoms of Alzheimer’s disease. All the information about their drinking and smoking habits as well as the age when the first symptoms of Alzheimer’s disease were noticed was obtained from close family members. We performed blood tests to detect the e4 variant for the gene for the ApoE protein. The e4 gene variant is known to increase the risk for Alzheimer’s disease and is also known to reduce the age at which Alzheimer’s disease occurs.

At the recent annual meeting of the American Academy of Neurology, in Chicago, I presented the results of our analyses of nearly 700 patients diagnosed with Alzheimer’s disease. As a group, their first symptoms started at the age of 75 years, but for those who drank alcohol moderately, did not smoke and did not have the e4 gene variant, the onset of symptoms was at 77 years of age. We found that each of the three risk factors, heavy smoking, heavy drinking and the e4gene variant, individually reduced the age of onset of Alzheimer’s disease by two to five years. When all three risk factors were present, the disease developed an average of 8.5 years earlier than in those with none of these risk factors. The findings, which need to be confirmed, raise many more questions which will need to be explored.
Moderate drinking helps

Although heavy drinking has been known to increase the risk, moderate alcohol consumption, which is generally defined as one to two drinks a day, has been shown to protect people from developing Alzheimer’s disease. The effect of smoking on Alzheimer’s disease has been somewhat controversial, because several earlier studies suggested that smoking protected people from developing Alzheimer’s disease. However, because regular smoking is so strongly associated with earlier death, it is now clear that these previous reports, showing a protective effect of smoking, were the result of what is known as “survivor bias” (i.e., those who smoke regularly and live long enough to develop age-related diseases are survivors and are genetically protected from developing many age-related diseases). Many previous studies have reported on the individual effects of these three factors (heavy drinking, heavy smoking and the ApoE e4gene) on the risk for developing Alzheimer’s disease, but the effect of these risk factors on lowering the age of onset of the disease has rarely been studied for smoking and drinking. Further, the combined risk for Alzheimer’s disease from these three factors has not been examined previously.

Alzheimer’s disease is rapidly becoming a burden for developing countries as well as developed countries. Mental and physical deterioration in this disease typically progresses gradually over a period of six to ten years from the onset, until death occurs. Caregivers of the patients often suffer emotionally and financially from the prolonged burden of observing the progression of the disease and caring for the patient. The disease has multiple victims because caregivers become much less productive as citizens and are more prone to developing medical and psychological problems, most likely because of the many stresses they have to bear. Although the importance of controlling risk factors for cardiovascular disease is well known to the public, delaying the age of onset of Alzheimer’s disease, which also has major public health benefits, has not been emphasised so far.
Similar risk factors

As it happens, all the factors that increase risk for heart disease are also associated with increased risk for Alzheimer’s disease. The results of this study provide an additional reason for moderation in drinking and avoiding smoking, apart from the benefits to the heart and other organs. Those with the ApoE e4 gene variant, who are already at higher risk for developing Alzheimer’s disease, should be especially vigilant about how much they drink and about avoiding smoking. Routine screening for the ApoE e4 gene variant has not been recommended as a public health measure, but the results of this study suggest that this may become appropriate. Other measures that are known to reduce risk for heart disease, such as avoiding obesity, doing regular exercise and eating a healthy diet, are equally important measures to be emphasised for preventing Alzheimer’s disease.

The symptoms

Loss of recent memory: Repetitiousness, forgetting names, recent conversations and events, getting lost in familiar places, misplacing things, forgetting appointments, to make payments, to take medications and to do chores.

Changes in behaviour: Irritability, anxiety, depression, paranoia (accusing people of stealing misplaced items), agitation, aggressiveness, childishness.

Physical symptoms (Usually in later stages of the disease): Walking slow, less stable, stiffness of muscles, frequent falls, incontinence of urine.

The risk factors

Age (prevalence doubles every five years after 65 yrs)

Family history (risk increases 2-3 fold, if a close family member is affected)

Apolipoprotein E e4 gene variant (increases risk 2-4 fold)

Presence of other neurological diseases (e.g., Parkinsons, strokes, head injury, Down Syndrome)

Cardiovascular Disease and risk factors (Hypertension, coronary artery disease, diabetes mellitus, smoking, obesity, lack of exercise, high cholesterol)

Social isolation, Depression, Anxiety states

Heavy alcohol consumption (moderate drinking may be protective)

Gender (women may be at slightly greater risk)

Ranjan Duara is a neurologist who has studied the diagnosis, risk factors and treatment for Alzheimer’s disease for the last 30 years. He is currently based at Mt. Sinai Medical Centre, Miami Beach, Florida.