Like thousands of other runners, Philip Posa, 45, of Westhampton took part in this year’s Boston Marathon to raise awareness for a cause important to him.

He ran the 26.2-mile marathon in 5 hours and 19 minutes to honor his mother, who died about 10 years ago of early onset Alzheimer’s at age 57, and in the hopes that the more than $80,000 he’s raised may help researchers find a cure for himself.

Posa, an executive at Deer Park-based FragranceNet, was diagnosed about a year and a half ago with mild cognitive impairment — a disorder that affects memory and other mental processes. He’s since developed a noticeable stutter and has difficulty “finding the right words” in conversation, noting that his 5-year-old daughter Lainey has begun to correct him when he trips up.

Posa now fears he may soon develop the disease that took his mother.

About 12 percent of people with Posa’s diagnosis will develop dementia within a year. More than 50 percent will be diagnosed with the disease within five years, according to Dr. Brent Forester, chief of the division of geriatric psychiatry at McLean Hospital outside Boston.

“I am normally a private person, but the time has come for me to speak out and fight Alzheimer’s,” Posa wrote in a companywide email sent last November in which he declared his participation in the marathon as part of the Run to End Alzheimer’s team.

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Posa has since raised $80,888 for the Alzheimer’s Association, making him the top individual fundraiser in Monday’s marathon. Friday, he threw out the first pitch at the Boston Red Sox 5-3 win against the Toronto Blue Jays.

“This started out as a goal that I had for myself, but has become so much more,” Posa said.

Angela Floro, director of the Run to End Alzheimer’s program, said Posa is the team’s first runner to participate in the marathon with mild cognitive impairment.

Posa is an experienced-long distance runner and, before his diagnosis, had participated in several endurance runs.

He said before the marathon he was confident his body could go the distance in Boston. But training for a marathon is a long, difficult process, and with his time-management abilities impaired, he wouldn’t have been able to stick to a training plan without the support of his wife Michele.

“I’m a young mom with a young husband. It’s been a challenge, and I’ve now taken on most of the household responsibilities,” Michele Posa, 35, said. “We’ve had good days when he seems perfectly fine, and we’ve had bad days. I’m just so happy that he’s sharing his story.”

Posa ran the marathon with the aid of two guides, who helped him deal with crowds and remain hydrated throughout the notoriously grueling 26.2-mile course.

Posa called it the “toughest” marathon he’d ever run; he averaged 12 minutes, 11 seconds per mile.

More than 40 people came to cheer Posa on as he crossed the finish line Monday afternoon, his wife said. Among them was another middle-aged man battling early onset Alzheimer’s.

“I’m glad that I could raise the money and raise awareness, but I was really moved to see that I can show other people going through this that they can still do what they’re passionate about,” Posa said.