Alzheimer's disease affects nearly 5 million Americans, a number that's expected to balloon to 13.8 million by 2050.
In its mildest form, the neurodegenerative condition is characterized by symptoms including memory lapses, getting lost, repeating questions, and misplacing things — behaviors that generally get more severe over time.
Genetic mutations are becoming increasingly important as a way to understand how Alzheimer's develops, both in late-onset and early-onset.
In the case of early-onset Alzheimer's, in which symptoms start showing in a person's 30s, 40s, or 50s, the disease is caused by genetic mutations in one of three genes that are inherited from a parent, according to the NIA.
There is not a known mutation that causes the late-onset disease, but there are some gene mutations that increase — and others that decrease — your risk.
While genetics can play a role, so might the environment that surrounds your family, according to the Alzheimer's Association. The organization noted that risk of Alzheimer's increases if more than one family member has the disease.
When it comes to how genetics and a person's environment relate to their risk of Alzheimer's, there's still a lot more research that needs to be done.
Unlike genetics and age, there are some risk factors you have some control over.
For example, managing other health conditions — diabetes and heart conditions such as high blood pressure, heart disease, stroke, and high cholesterol — may increase a person's risk of Alzheimer's disease, according to the NIA. More research is needed to understand these risk factors, and some clinical trials are already underway, but it the connections bolster the idea that what's good for your heart could also be good for your head.
According to the Alzheimer's Association, trauma to the head is potentially associated with an increased risk of the disease down the line. That's based in part on observational research involving veterans from World War II. Those who had either moderate or severe brain injuries during their military service were found to have an increased risk of developing Alzheimer's disease or dementia later in life.
Of course, the researchers noted, there could be other factors not taken into account in the study that might have influenced that association.
The AA recommends using helmets, wearing seat belts, and "fall-proofing" your home to decrease your chances of getting a serious brain injury.
A few lifestyle choices can also contribute to your risk of Alzheimer's. According to the World Health Organization, smoking is associated with an increased risk of dementia and Alzheimer's. Researchers think this has to do with the vessels that carry blood around our body and to our brains, which are also involved in things like stroke and heart disease.
Other unexpected factors can decrease your risk of the disease
Diet, exercise, social activity, and more have been all linked with decreased risk of Alzheimer's and cognitive decline. In fact, there are several surprisingly easy ways you can lower your chances of getting the disease.
Discover More Like This
BACK TO SLIDE
There's still a lot we don't know about the causes of Alzheimer's, but there are some factors associated with an increased risk of getting the disease. For the most part, though, an increased risk doesn't mean a person will necessarily get the disease —just that the chances are higher.
Here's what the science has to say about the factors that influence your risk of Alzheimer's and cognitive decline.
RELATED: Famous faces with the disease:
Notable people with Alzheimer's
Notable people with Alzheimer's
This file photo dated 04 November, 1991 shows US President Ronald Reagan giving a speech at the dedication of the library bearing his name in Simi Valley, California. He was US president from 1981 to 1989 and retreated from public life after it was revealed he was suffering from Alzheimer's disease. (Photo by J. David Ake, AFP/Getty Images)
Glenn Campbell performs during The Goodbye Tour at the Ryman Auditorium on January 3, 2012 in Nashville, Tennessee. (Photo by Ed Rode/Getty Images)
Picture dated 18 May 1991 of US actor Charles Bronson during the 44th Cannes film festival, southern France. Bronson died 30 August 2003 in Los Angeles of complications from pneumonia. (Photo by Gerard Julien, AFP/Getty Images)
392653 01: Actor Burgess Meredith performs in the television show 'The Twilight Zone.' (Photo Courtesy of Sci Fi Channel/Getty Images)
LOS ANGELES - AUGUST 31: Actor James Doohan recieves his star on the Hollywood Walk of Fame August 31, 2004 in Los Angeles, California. (Photo by Mark Mainz/Getty Images)
LONDON, UNITED KINGDOM - JANUARY 17: Malcolm Young of AC/DC performs on stage at Wembley Arena on January 17th, 1986 in London, United Kingdom. (Photo by Peter Still/Redferns)
NORMAN ROCKWELL'S AMERICA -- Pictured: Artist Norman Rockwell -- (Photo by: Gary Null/NBC/NBCU Photo Bank via Getty Images)
Publicity close up of Hollywood actress Rita Hayworth wearing ornately decorated gloves and holding a cigarette in a cigarette holder.
NEW YORK CITY - FEBRUARY 29: Aaron Copeland attends 10th Annual Grammy Awards on February 29, 1968 at the New York Hilton Hotel in New York City. (Photo by Ron Galella, Ltd./WireImage) (Photo by Ron Galella, Ltd./WireImage)
Actor Peter Falk poses as he arrives for the premiere of his new film
"Lakeboat" September 24, 2001 in Los Angeles. The film is an adaptation
of David Mamet's comic play about a grad student who takes a summer job
on a Great Lakes freighter and sees life through the eyes of his
low-brow crew members. The film opens in limited release in Los Angeles
September 28. REUTERS/Rose Prouser