Age
The biggest risk factor for Alzheimer’s disease is increased age. The likelihood of developing Alzheimer’s disease doubles every 5.5 years from 65 to 85 years of age. Whereas only 1%-2% of individuals 70 years of age have Alzheimer’s disease, in some studies around 40% of individuals 85 years of age have Alzheimer’s disease. Nonetheless, at least half the people who live past 95 years of age do not have Alzheimer’s disease. As we age, our body’s self–repair abilities become less efficient. This change occurs in the brain at different rates in different people.

Family History and Hereditary
If someone in your family had Alzheimer’s disease, then you are at greater risk of having this disease. Researchers believe that hereditary and Alzheimer’s disease are related, but they are not sure.

Apolipoprotein E-4 (ApoE) gene
The apoE gene has three different forms – apoE2, apoE3, and apoE4. Study has shown that, the apoE4 form of the gene has been associated with increased risk of Alzheimer’s disease in most people. Everyone has a double set of genes, one from each parent. ApoE4 is one variant of the apoE gene. If a person’s pair of apoE genes has one apoE4, they have three times the normal risk of developing Alzheimer’s disease, but if they carry two apoE4 genes the risk increases to ten times. However, people with no apoE4 genes can still get Alzheimer’s disease and people with two apoE4 genes will not necessarily get the disease. Although the genes are there from birth, they can’t cause Alzheimer’s disease on their own. The brain has to reach a certain critical age for the disease to occur.

Researchers are actively looking for evidence of other quite normal genes that may cause Alzheimer’s disease.

Diabetes
It has been known for some time that type 2 (adult) diabetes is a risk factor for Alzheimer’s disease. It was assumed that this was because the blood vessel and heart disorders associated with diabetes are also risk factors for Alzheimer’s disease. It is also known that the utilization of glucose is impaired in the brains of people with Alzheimer’s disease, somewhat resembling the situation in the bodies of people with diabetes. New research tells us that the impairment in the Alzheimer brain may be because the brain is in a sort of diabetic state, even though the person may not be diabetic in the ordinary sense. It seems, that in the brain of a person with Alzheimer’s disease, either the production of insulin in the brain is reduced for some reason or the brain cells are becoming insensitive to insulin.

Down Syndrome
Almost all individuals with Down syndrome over the age of 40 have changes to brain cells as of individuals with Alzheimer’s disease. Alzheimer’s disease usually develops when these individuals are in their 50s or 60s.

Head injury
Brain injuries, especially repeated concussions, are risk factors for Alzheimer’s disease which is developed later.

Menopause in Women
Women are at greater risk of having Alzheimer’s disease than men. The possibility is twice for women to get Alzheimer’s disease than men. This is partly due to their living longer than men on average, partly because women are more prone than men to get diabetes, but also in large part because in post–menopausal women there is a decrease of hormone estrogen. For many years, estrogen has been prescribed to relieve symptoms of menopause. Despite a recent large–scale clinical study on women which recommended discontinuation of Hormone Replacement Therapy (HRT) because it was both ineffective and had potentially dangerous side effects. Any decision regarding the use of HRT should be made after consulting a physician.

Reducing the risk
Living a healthy lifestyle may help reduce one’s overall risk of developing Alzheimer’s disease. A healthy lifestyle includes taking healthy diet, maintaining a healthy weight, doing regular physical activity, maintaining normal blood pressure and cholesterol levels and participating in activities that involve socializing and stimulating brain activity. In studies of identical twins (who share the same genes) it was found that about 60% of the overall risk for sporadic Alzheimer’s disease comes from lifestyle and not genetics.