How Common Is Alzheimer's Disease?
When looking at health and disease, statistics and epidemiology can be helpful in terms of trends in diagnosis, identifying risk factors and at-risk populations, and aid in putting together screening, diagnostic, and treatment programs. While statistics are not a be-all, end-all, and often only provide correlations that may or may not indicate causation, and should certainly be placed in context, they can be a valuable tool for researchers, doctors, and even patients and their families.
What is epidemiology?
Epidemiology enables us to see and understand the number of people who have a disease or condition, potential environmental factors, as well as age groups in which it occurs, as well as risk factors. It is an area of medicine that looks at the factors that make up the presence or absence of diseases.1 It also tracks the spread of disease and how diseases are spread, and the changing demographics of disease and health.
How common is Alzheimer’s disease?
In the United States, there are approximately 5.8 million individuals living with Alzheimer’s disease.2 Of these individuals, the majority (about 5.5 million) are age 65 or older, and about 200,000 individuals younger than 65 who have early-onset Alzheimer’s disease – although the actual prevalence of early-onset Alzheimer’s might be higher.2 What does this all mean? Nearly 1 in 10 individuals 65 and older has Alzheimer’s disease.2 The percentage of those with Alzheimer’s also increases with age: of those diagnosed, 81% are 75 years old or older.2
Worldwide, in 2017 it was estimated that approximately 50 million people were living with Alzheimer’s disease or a related type of dementia.3 It is thought that this number will nearly double every 20 years, with higher increases in developing countries.3 There are 9.9 million new diagnoses of dementia every year.3 More than half of the world’s Alzheimer’s or dementia patients (58%) live in low or middle-income countries, where healthcare is not as advanced, or access to healthcare is not easily accessible.
Figure 1. Prevalence of people with dementia in low and middle income countries compared to high income countries
Who gets Alzheimer’s disease?
Almost two-thirds of Americans diagnosed with Alzheimer’s are women.2 Of the previously mentioned 5.5 million people with Alzheimer’s disease, 3.4 million are women and 2.1 million are men.2 There are several hypotheses for this, including the fact that women tend to live longer than men, and older age is the most important risk factor for Alzheimer’s disease. More research is being done as to whether there are biological or genetic factors to this.
Non-Hispanic Caucasians make up the largest racial or ethnic group in the United States to be diagnosed with Alzheimer’s; however, African Americans and Hispanics are more likely, per-capita, have Alzheimer’s disease.2 Older African Americans are almost twice as likely as older Caucasians to have Alzheimer’s disease, and older Hispanics are approximately one and a half times as likely to be diagnosed with Alzheimer’s than older Caucasians.2
Risk factors for Alzheimer's disease
Risk factors are factors that can increase the likelihood of developing said disease. Having one or more risk factors does not mean you definitely will develop the disease; it simply means your risk of developing it may be higher. If you don’t have any risk factors, this also doesn’t mean that you definitely won’t develop the disease – you can still develop it, but your risk of developing it is lower. Risk factors for Alzheimer’s disease include4:
- Age: Increasing age is the biggest known risk factor for Alzheimer’s disease. Although Alzheimer’s is not a typical or normal part of getting older, the older you get, the more likely you are of developing Alzheimer’s disease
- Family history/genetics: If you have a first-degree relative with Alzheimer’s, your risk is slightly higher, although much of the genetics are unknown. There are very rare mutations in three genes that have been studied in the development of Alzheimer’s disease; if you have a family member with the disease and are concerned about your own risk, talk with your doctor about the risks and benefits of genetic testing
- Down syndrome: This may be related to having three copies of chromosome 21, which means three copies of a gene for the protein that leads to more beta-amyloid, which creates the plaques in Alzheimer’s disease
- Past head trauma
- Lifestyle factors and heart health: The risk factors for heart disease are also associated with a higher risk of Alzheimer’s disease, including obesity, a sedentary lifestyle, smoking cigarettes, and high blood pressure and cholesterol
Statistics and epidemiology are wonderful tools that help give us a broader view of disease and health, but they should be seen as part of the larger picture. A patient is not a number or statistic, and there will always be individual factors that come into play.
