This strong tendency of Alzheimer’s disease to run in families is due, in part, to mutations in certain genes. About five percent of all Alzheimer’s disease is caused by a mutation in one of three genes, called APP, presenilin 1 (PS1), and presenilin 2 (PS2). Each of these genes is inherited in a dominant fashion. Although each mutation is different, they all occur in the same region of the gene.

APP Gene

More than 25 different mutations in the APP gene can cause early-onset Alzheimer disease. These mutations are responsible for 10 percent to 15 percent of all early-onset cases of the disorder. The APP gene provides instructions for making a protein called amyloid precursor protein. This protein is found in many tissues and organs, including the brain and spinal cord. Mutations in the APP gene can lead to an increased amount of the amyloid beta peptide or to the production of a slightly longer and stickier form of the peptide.

Certain mutations in the APP gene can also result in brain abnormalities other than Alzheimer disease. For example, a particular APP mutation causes a disorder called hereditary cerebral hemorrhage with amyloidosis-Dutch type.

PSI Gene

People with mutations in PS1 develop Alzheimer’s disease at the earliest age, ranging from 29 to 62 but with an average age of 44 years. PS1 is on chromosome 14. Families with a particular PS1 mutation tend to develop Alzheimer’s at the same age. Localization of PS1 immunoreactivity in familial and sporadic Alzheimer’s disease suggests that genetically heterogeneous forms of the disease share a common pathophysiology involving PS1 protein.

The normal biological role of PS1 as well as the mechanism by which mutations in PS1 cause FAD remains unknown.

PS2 Gene

The PS2 gene is more rare and causes symptoms to appear between 40 and 85. Unlike the PS1 or APP genes, researchers have found people who have a mutation in the PS2 gene but did not develop Alzheimer’s disease. What has been found is that the gene’s mutations have been found in only six different families with Alzheimer’s disease—five German families and one Italian family.The PS2 gene is required for some forms of cell death in diverse cell types.

How do we inherit out genes?

Humans inherit 23 chromosomes from each of their parents for a total of 46 chromosomes. Of these, 44 are identical in men and women, these are called autosomes. The remaining two chromosomes are called sex chromosomes, which are designated X and Y. Women inherit two X chromosomes, whereas men inherit one X chromosome from their mother and one Y chromosome from their father.

Preventing Alzheimer’s Before the Onset

Alzheimer’s is a multi-faceted disease and efforts to understand it have followed a variety of paths. One line of research focuses on the endings of nerve cells in the brain, which degenerate as the disease progresses. Lifestyle choices can protect your brain.

  • Challenge your brain
    • Consider your brain a muscle, and find opportunities to flex it. Read, read, read. Using the brain actually increases the number of dendritic branches that interconnect brain cells. The more we think, the better our brains function, regardless of age. If you are right-handed start writing with your left hand. Change the color of a room or rearrange the furniture so that your mind will have to coordinate or adjust to the change. Stimulate the brain by traveling to a different state. Eat foods that you would never consider eating. Learn a new language.
  • Exercise
    • If you exercise 30 minutes a day, try working out for an additional 30 minutes. Walking improves your memory and supplies oxygen to your brain. Running is a great brain booster. Exercising improves the heart’s ability to pump blood more effectively to the brain.
  • Stay socially active
    • Starting or joining a social group with other elderly peers is one way to become socially active. Enjoying the same interests and outings will boost your immune system. Even routine activities such as gardening, cleaning, or doing laundry with another companion can increase your level of contentment.
    • Visiting grandchildren or children in hospitals or reading to children at your local library stimulates your brain. Attend a different museums each month with family or friends. Most museums fees are free or reduced for senior citizens.
    • Volunteer at a community center or non-profit center that can use your expertise.
  • Staying Mentally Active
    • Relaxation is the key to controlling your mental state during a stressful time. Getting plenty of sleep and taking a nap at a regularly scheduled time not only relaxes you but keeps your body on a schedule.
    • Regular meditation, prayer, reflection, and religious practice may immunize you against the damaging effects of stress.
    • Eliminating stress from your life is a major factor in taking care of your brain and staying mentally active.
  • Visit loved ones and friends
    • Commit to spending quality time with loved ones and friends by leading a brain-healthy lifestyle, you may even be able to prevent the symptoms of Alzheimer’s disease entirely and slow down, or even reverse, the deterioration of aging.