Last Updated Jul 21, 2015 7:27 PM EDT
About eight years ago, Allan Vann's wife, Clare, began forgetting things. It started out small: she would get them lost during their many trips to foreign countries despite her usual sharp sense of direction, or she would leave her sweater or pocketbook at a restaurant. But over the next two years, things progressively got worse.
"She started to develop what I called the 'Groundhog's Day syndrome,' asking me the same question over and over and over," Vann, 68, a retired school principal, told CBS News chief medical correspondent Dr. Jon LaPook. "She was putting refrigerated food in cabinets and food from cabinets she was putting into the refrigerator. She couldn't maintain her calendar, just all sorts of organizational problems."
In 2009, Clare, a former teacher who is now 69, was diagnosed with Alzheimer's disease. She has lived in an assisted living facility for the past two years, which gives her the 24/7 care she needs as the disease claims more and more of her mental and physical function. Allan visits her daily. After 48 years of marriage, "She knows I'm her husband but doesn't always remember the word husband. So basically she knows that I am somebody she loves, and she knows I am somebody who loves her," he said.
For many Americans, Allan and Clare's story is all too familiar. Over 5 million people in the United States currently live with Alzheimer's disease and one in three seniors dies with the disease or another form of dementia, according to the Alzheimer's Association.
Women are disproportionately affected. Almost two thirds of Americans with Alzheimer's disease are female. And by age 65, women without the disease have more than a one in six chance of developing Alzheimer's during the remainder of their lives, compared with a one in 11 chance for men.
In addition, new research presented Tuesday at the Alzheimer's Association International Conference in Washington, D.C., finds that women at risk for Alzheimer's and dementia decline dramatically faster than at-risk men.
Researchers from Duke University Medical Center looked at about 400 men and women, mostly in their mid-70s, with mild cognitive impairment, a condition involving a slight but noticeable decline in memory and thinking skills. Over the course of up to eight years, the data showed that the cognitive abilities of the female participants declined twice as fast as their male counterparts.
"These results point to the possibility of as yet undiscovered gender-specific genetic or environmental risk factors that influence the speed of decline," lead researcher Katherine Amy Lin, the Wrenn Clinical Research Scholar in Alzheimer's disease at Duke University Medical Center, said in a statement. "Uncovering those factors should be a high priority for future research."
Another study also presented at the conference found that among older adults, women are more likely than men to experience a decline in brain function and cognition after undergoing surgery with general anesthesia, and those women declined at a much faster rate.
Experts said research now needs to focus on the causes of the gender differences in order to better understand why women face higher risk, and potentially to improve prevention methods and treatment options.
"Women are disproportionately affected by Alzheimer's, and there is an urgent need to understand if differences in brain structure, disease progression, and biological characteristics contribute to higher prevalence and rates of cognitive decline," Alzheimer's Association Chief Scientific Officer Maria Carrillo said in a statement. "To intervene and help reduce the risk of Alzheimer's, it's critical to understand the reasons for these differences."
For the Vanns, Allan knows that at some point, Clare's mind will deteriorate to the point of no return, but he has vowed to be with her every step of the way.
"Seeing her every day is as much for me as it is for her," he said. "I want to keep that bond that we have for as long as I can."