Understanding What “Causes”, “Risk Factors” and “Links” Mean with Alzheimer’s & Dementia

Have you heard or read something that left you more confused after? Coming across phrases like this is a “risk factor” for dementia, something “increases the chances” of getting Alzheimer’s by 50% or not sleeping well has been “linked to” cognitive impairment all sound similar and can leave you with an unclear meaning.

What do all these terms even mean? Every other day, it seems there are media reports associating Alzheimer’s with some seemingly harmless, daily activity. Can risk factors be controlled? Why are they so often numerical, like how can what I eat make me “50 percent less likely” to have a disease? Does an unhealthy diet, or decades of bad habits, cause Alzheimer’s?

Definitions

“Causes”

Saying something is a “cause” requires a case-control study. For example, to show smoking causes lung cancer scientists must isolate lung cancer sufferers (the case) from people with other deadly illnesses (the control) and find out how many people in each group smoked. The numbers were so overwhelming, with such a high percentage of lung cancer patients smoking compared to the control group that experts agreed smoking could be considered a cause of lung cancer.

You could still argue we do not know the cause because some people who smoke do not get lung cancer. Determining causes is rarely definitive, which is why the term “risk factors” is widely used.

“Risk Factors”

In the above example, scientists showed causation between an act, smoking, and a disease, lung cancer. There is no such act that leads to Alzheimer’s. Instead, the disease grows out of multiple risk factors that include genetics, lifestyle habits, and environment.

Think of “risk factors” meaning something having a higher likelihood to happen. If two people are the same, except one of them has a family history of dementia, then that person has a higher percentage and likelihood of getting the disease. Another example is that if two people are the same except one of them has had concussions, then that person has a higher percentage likelihood of developing Alzheimer’s. Genetics and head injuries are risk factors that increase the potential for dementia.

“Linked To” or “Associated With”

“Linked to” or “associated with” is similar to saying something is a risk factor, except it is weaker and oftentimes meaningless. Another difference is that these terms can imply something positive.

Think of it as hedging a bet. For example, recent findings in a study led by the Boston University School of Medicine showed that regular consumption of artificial sweeteners in diet soda increases a person’s risk of Alzheimer’s. Other sources have disputed this, and even the authors of the study said their results “only show a trend among one group of people.” No one would call being a diet soda drinker a “risk factor” for developing dementia because that language would be too strong. In turn, articles say that the consumption of artificial sweeteners has been “linked to” an “increased risk of” dementia.

“Linked to” is also different because it can be positive. A healthy diet has been “linked to” decreased risk of dementia: The Mayo Clinic has said the proper diet can cut a person’s risk of dementia by 53 percent, which brings us to the usage of percentages.

Percentage Increase or Decrease

You hear all the time that something increases or decreases risk by a certain percentage. There are many statements that use percentages, like:

• Eating healthy lowers your odds of dementia by 53 percent.
• Every five years after 65, the chances of developing Alzheimer’s double.
• Someone with diabetes is 65 percent likely to get Alzheimer’s.

These numbers need context because they are not always as scary as they seem. Think of yourself as one in a group of 100 people. Ten percent of the population, on average, develops Alzheimer’s between 65 and 75, so 10 out of the 100 will get it. How likely you are to be among those 10 is where the percentage increases and decreases. If you eat healthy, there are about 50 people who are more likely to be among the 10 than you.

If you have diabetes, you move closer to the 10, but if someone with diabetes is 65 percent likelier to get Alzheimer’s, that doesn’t mean 65 out of 100 people with diabetes get Alzheimer’s. It means that within the group of 100, those with diabetes are 65 percent more likely than those without diabetes to be among the 10 with Alzheimer’s. It provides a relative understanding of where you are, compared with everyone else. Even that can’t be exact because other factors like diet skew the percentage.

Epidemiologists, a scientist studying diseases in populations, say that calculating risk is complicated and error-prone. Use these numbers as basic guidelines, and focus on risk factors you can control.

Risk Factors We Control

There are many risk factors that are tied to the development and onset of Alzheimer’s. Some key risk factors are:

• Being over 65 is a risk factor, and every five years the risk of developing Alzheimer’s doubles. About 10 percent of people between ages 65 and 75 have Alzheimer’s, but more than 40 percent have developed it by 85. Age is something we cannot control.
• Family history. We can not control family history or genetics. Alzheimer’s patients’ family medical history is not such a risk factor compared to patients with other forms of dementia. This would be like early-onset Alzheimer’s and Huntington’s disease where experts say that someone with a familial history of the disease has a higher percentage to develop it.
• Smoking has been linked to an increased risk of Alzheimer’s because it can decrease the circulation of blood to the brain.
• Not exercising enough is also a risk factor. Maintaining a healthy cardiovascular system decreases the risk of Alzheimer’s.
• Head injuries have been linked to developing dementia later in life because an impact on the brain can cause plaques to form. Protecting your head by wearing a helmet while bike riding and always buckling the seat belt in your car is an easy prevention.
• A bad diet is an increased risk factor. Increase your odds of delaying the onset of dementia by eating brain foods including leafy greens and other colorful vegetables, nuts, berries, beans, whole grains, fish, chicken, and olive oil.

More on the causes of Alzheimer’s and risk factors for dementia.