While scientists know that Alzheimer’s disease involves the failure of nerve cells, it’s still unknown why this happens. However, they have identified certain risk factors that increase the likelihood of developing Alzheimer’s.
The greatest known risk factor for Alzheimer’s is increasing age. Most individuals with the disease are 65 and older. One in nine people in this age group and nearly one-third of people age 85 and older have Alzheimer’s.
Another risk factor is family history. Research has shown that those who have a parent, brother or sister with Alzheimer’s are more likely to develop the disease than individuals who do not. The risk increases if more than one family member has the illness.
Familial Alzheimer’s and genetics
Two categories of genes influence whether a person develops a disease: risk genes and deterministic genes. Risk genes increase the likelihood of developing a disease but do not guarantee it will happen. Deterministic genes directly cause a disease, guaranteeing that anyone who inherits one will develop a disorder.
Researchers have found several genes that increase the risk of Alzheimer’s. APOE-e4 is the first risk gene identified and remains the one with strongest impact. Other common forms of the APOE gene are APOE-e2 and APOE-e3. Everyone inherits a copy of some form of APOE from each parent. Those who inherit one copy of APOE-e4 have an increased risk of developing Alzheimer’s; those who inherit two copies have an even higher risk, but not a certainty.
Rare deterministic genes cause Alzheimer’s in a few hundred extended families worldwide. These genes are estimated to account for less than 1 percent of cases. Individuals with these genes usually develop symptoms in their 40s or 50s.
Latinos and African-Americans
Research shows that older Latinos are about one-and-a-half times as likely as older whites to have Alzheimer’s and other dementias, while older African- Americans are about twice as likely to have the disease as older whites. The reason for these differences is not well understood, but researchers believe that higher rates of vascular disease in these groups may also put them at greater risk for developing Alzheimer’s.
Other risk factors
Age, family history and genetics are all risk factors we can’t change. However, research is beginning to reveal clues about other risk factors that we may be able to influence. There appears to be a strong link between serious head injury and future risk of Alzheimer’s. It’s important to protect your head by buckling your seat belt, wearing a helmet when participating in sports and proofing your home to avoid falls.
One promising line of research suggests that strategies for overall healthy aging may help keep the brain healthy and may even reduce the risk of developing Alzheimer’s. These measures include eating a healthy diet, staying socially active, avoiding tobacco and excess alcohol, and exercising both the body and mind.
Some of the strongest evidence links brain health to heart health. The risk of developing Alzheimer’s or vascular dementia appears to be increased by many conditions that damage the heart and blood vessels. These include heart disease, diabetes, stroke, high blood pressure and high cholesterol. Work with your doctor to monitor your heart health and treat any problems that arise.
Studies of donated brain tissue provide additional evidence for the heart-head connection. These studies suggest that plaques and tangles are more likely to cause Alzheimer’s symptoms if strokes or damage to the brain’s blood vessels are also present.