Risk Factors for Alzheimer's Disease

risk factors for alzheimer's disease


Alzheimer’s Disease (AD) is a progressive neurodegenerative disease that can progress over many years. It is a complex disease that can progress like other chronic diseases such as diabetes and cardiovascular diseases. It gets worse with increasing age and time. People who develop late onset of AD faces problems in everyday activities such as bathing, eating and dressing, and need help from others. Also, people with AD experience memory loss (forget names, familiar faces, people and places, repeat conversation or forget it etc) and other cognitive impairments at early stages of the disease.

Some risk factors for Alzheimer’s cannot be controlled such as age and genetic heredity. But there are number of other factors that influence a person to develop Alzheimer’s. These factors are preventable and if checked and controlled by a person, may reduce the chances of developing it. The symptoms may sometimes be triggered by a combination of these factors. Risk factors are classified into two broad categories:

  •  Modifiable Risk Factors
  •  Non-Modifiable Risk Factors

There are certain risk factors which cannot be modified and may lead to AD, but others may be modified and may depend upon the lifestyle of a person.

Non-Modifiable Risk Factors

It is generally observed that Alzheimer’s occurs during an old age that is in 60s and above. Sometimes genetic mutation especially in APOE (apolipoprotein E) e-4 gene may trigger early onset of the disease. Alzheimer’s although is not due to the normal process of ageing and does not affect every old individual, but ageing is considered as a risk factor for developing the disease. The risk of getting it increases with increase in age. It is estimated that 1 in every 20 Canadian over the age of 65 and 1 in every 4 over the age of 85 years have Alzheimer’s.

The ‘Alzheimer’s Association’ found that 1 in every 9 people over the age of 65 years and 1 in every 3 people over the age of 85 years has Alzheimer’s.

It is also estimated that 5% of Americans between 65-74 years of age have Alzheimer’s. This count increases to almost 50% in people over the age of 85 years. In the United States (US), a majority of people get late onset of AD generally after 60 years.

It is a well established fact that ageing impairs your body’s self-repairing mechanism such as DNA replication and cell regeneration process get slowed down and becomes faulty. These self-repair mechanism defects cause brain impairments too. The factors and impairments associated with ageing which lead to AD or dementia like symptoms are –

  • Cardiovascular diseases such as stroke and heart disease
  • High cholesterol level
  • High blood pressure
  • Changes in DNA and cell structure
  • Lower sex hormone level at mid-age or later years 
  • Improper functioning of body’s repair mechanism

Genetic (Hereditary) and Genes

In most of the cases, Alzheimer’s is not inherited in family. It is called as Sporadic Alzheimer’s Disease. Scientists found and observed from researches and studies that generally early onset of Alzheimer’s is related to APOE protein gene mutation or mutation in any of their subtype i.e. APOE (apolipoprotein E) e-2, e-3, e-4 protein gene. These protein genes are called as risk factor genes, as people with these genes are at risk of getting the disease. Late onset of AD is not commonly related to any of these gene mutations. There are certain deterministic genes which if present in an individual may lead to AD.  Early onset of AD is generally seen in 5% of the population and is known to be inherited in families. This is called as Familial Alzheimer’s Disease. Familial AD definitely develops in people with any of the three deterministic protein genes (amyloid precursor protein (APP), presenilin-1 (PS-1) and presenilin-2 (PS-2) mutation. Any person with these three deterministic genes definitely develops AD at any stage of his/her life.

The inheritance of any of the risk factor genes doesn’t necessarily cause AD. But it puts a person on higher risk of getting the disease.

Thus, it may be possible for a person to develop AD due to inheritance. If your family has a history of Alzheimer’s or your siblings are suffering from it, there are chances that you may develop it sometime in your life.


It is estimated that 1 out of 3 women likely gets Alzheimer’s and have more chances of getting this disease than men. The fact of women getting it more than men is due to the reason that women live longer than men. But it is not an evidence to prove the assumption why women get affected more than men.

It is observed that AD is related to the lack of estrogen hormone in women after menopause but it’s not true because even Hormone Replacement Therapy doesn’t help reduce symptoms of Alzheimer’s.

Modifiable Risk Factors

Head Trauma and Brain Abnormalities

People who get head injuries are at higher risk of getting Alzheimer’s. This risk increases if they get ‘contact sports’ (losing their consciousness which happens continuously) during injury.

A study done on World War II Veterans shows that veterans with moderate to severe head injuries were at higher risk of developing AD and other dementia. Dementia pugilistica is a name for dementia caused by brain damage due to repeated head traumas. This condition affects around 20% retired professional boxers. The term Chronic Traumatic Encephalopathy(CTE) is used for long term neurological side-effects which happen due to repeated and sustained head injuries to boxers. These trauma conditions may increase the risk of developing Alzheimer’s in these professionals.

People with Mild Cognitive Impairments (MCI) which include memory problems and other cognitive function impairments that may worsen over time may be at high risk of getting Alzheimer’s or developing dementia. This may not certainly happen but the risk of Alzheimer’s or dementia is increased at later stages of life.

Scientists also observed that brain abnormalities such as formation of plaques and nerve fibre tangles may risk a person for developing Alzheimer’s. Brain tissue shrinkage, inflammation and loss of brain cells connections are early signs that depict chances of developing Alzheimer’s.


Smoking is linked to various conditions and diseases such as cancer, stroke, diabetes, and heart diseases. There is strong evidence that smokers are at 45% more risk than non-smokers for developing Alzheimer’s. Smokers are also at risk of developing vascular dementia but evidences for it are not very strong. It is found that people who quit smoking or ex-smokers reduce the risk of Alzheimer’s. 

An article which is published in the American Journal of Epidemiology concluded after study and examination of previous 19 studies that people who are currently smokers are at higher risk of developing AD than non-smokers. 

Limited physical activities and obesity

Lack of regular exercise and physical activity can make you more prone to AD. Regular exercise leads to a healthier and longer life. It helps in prevention and controlling over 20 chronic disease conditions and reduces stress and depression and ultimately improves your mental health and well-being.

It also helps in maintaining Body Mass Index (BMI) and a healthy weight. It is observed from researches that obesity may triple the risk of developing AD in people in midlife.Obesity is also linked with other health conditions like diabetes and high blood pressure. Therefore, maintaining a healthy weight and keeping yourself fit is important to avoid risk of getting any disease or impairments during the lifetime. These reasons may also contribute to mental problems and therefore, a regular exercise helps in reducing the risk of AD in later years.


Recent studies found that type 2 diabetes during 30s is linked with an increased risk of Alzheimer’s disease, dementia and other cognitive impairments. It is also found that diabetes increases the risk of AD by 65% in people. People who have type 2 diabetes are twice on risk of developing diabetes than non-diabetic people.

High Blood Pressure and Alzheimer’s

High blood pressure increases the risk of AD especially in midlife. Researchers found that high blood pressure at a middle age may increase the risk of Alzheimer’s in later years of your life. High blood pressure generally affects blood circulation, heart and arteries, thus increasing the risk of Alzheimer’s, and particularly the risk of developing vascular dementia. Treating high blood pressure with exercise and proper diet can reduce the risk of getting AD.

High Cholesterol Levels as Risk Factor for Alzheimer’s Disease

Cholesterol is necessary for brain functioning as it is a cell membrane component and required for cell repair and making new connections between nerve cells. However, high cholesterol levels at middle age or later years can increase the risk of AD and dementia. People with high cholesterol are likely to develop AD as compared to people with normal cholesterol levels. Researchers showed that treating cholesterol with drug statin lowers the risk of AD and other dementia conditions.

High Homocysteine Levels as Risk of Developing AD.

Certain studies found that Homocysteine, which is a by-product of many metabolic reactions and occurs in our body, if increases may increase the risk of AD and dementia-related conditions in people. Taking Vitamin B and folate can help in reduction of homocysteine levels and also lower the risk of Alzheimer’s.

Unhealthy and Poor Diet

Poor and unhealthy diet may lead to much impairment in our body such as fatigue, weakness and other disease conditions due to lack of immunity. Even proper diet and vitamins are needed for proper cell functioning and nourishment. Lack of vitamins and minerals due to poor or unhealthy diet may lead to lack of nourishment to cells which may lead to cell abnormalities and improper functioning and gradually cell damage. It is seen that people with poor diet have higher incidences of Alzheimer’s. A proper and healthy diet seems to improve many disease conditions and reduce the chances of developing Alzheimer’s disease and other brain related diseases.

Foods like butter, cakes and meats are full of saturated fats which may lead to increase in cholesterol levels and can cause excess weight gain thereby increasing the risk of cardiovascular diseases and other health problems like dementia and Alzheimer’s.

A heavy sugar intake may lead to weight gain and Type 2 diabetes. Snacks like cakes, cold drinks, sweets and chocolates are high in sugar and should be eaten in limited amount so as to avoid getting diabetes and reduce the risk of AD and dementia-like conditions.

Learning and Social Engagements

Researchers showed that education reduces the risk of Alzheimer’s and dementia. Some activities link lower risk of Alzheimer’s to more education time while others relate it to leisure activities. But there is exactly no clear idea about which type of activity lowers the risk of AD. It is though suggested to do things that make you happy and socialise you as well to avoid depression. Depression may lead to AD. Being mentally active helps in mental well-being and makes you feel happy and think positive. 

Mental challenges include such as – getting higher education, learning new games, learning new instruments, working in job of interest, playing puzzle games etc. These make your cognitive function well. One theory is that through these activities your brain develops new neurons and connections between nerves and particular neurons which reduce the risk of AD and dementia. It is usually seen that people with an active mind and engaged in mental activities are likely to be healthier and avoid developing AD and dementia.

Down syndrome and AD

It is seen that many people with Down Syndrome develop AD symptoms 10-20 years earlier than normal people. An extra gene in chromosome that causes this syndrome may likely be the reason for the higher risk of AD in such people.

Alcohol Intake

Alcohol accounts for more than 200 disease and injuries including non-communicable diseases such as cancer, cardiovascular diseases, and liver cirrhosis and is also a risk factor for death and disabilities, thus ranked 5th among all risk factors for these conditions. Studies have mixed results for whether it is linked to a higher risk of dementia and AD. However, heavy drinking may lead to alcohol related-dementia which also includes Wernicke-Korsakoff Syndrome.

People who drink less alcohol or who are non-drinkers are at lower risk of developing Alzheimer’s and dementia.