Sept. 8, 2009 -- When Diane Thornton first realized she was having trouble keeping track of appointments, she would write herself reminder notes. When she got lost on her way to the office, she'd call her secretary and ask for directions. On days she had trouble speaking or remembering words, she would avoid answering her phone.
But when in her psychotherapist practice she could not remember her patients' names, could not recognize the notes she had written in their files, could not understand the mounting paperwork it took to handle their claims, and could not trust herself not to say inappropriate things -- she knew there would be no quick fix, no easy cover up.
She would have to quit, and face the fact that at age 52 she had dementia.
Though she admits she has "no reference for time" and difficulty "remembering when things happened," she remembers one date in particular.
"August 15, 2006. That date really sticks on the brain. That's when I left my job. That's the day I lost my identity," Thornton said.
Thornton, now 55, is one of the 200,000 Americans under age 65 estimated to be living with early onset dementia or Alzheimer's disease. Dementia, and its often attendant cause Alzheimer's, is marked by memory loss and declines in language and cognitive function. While it typically affects people in the final years of life, early onset dementia sometimes strikes people in their prime.
For a retiree with adult children, dementia is a frightening prospect. But for a middle-aged person with a mortgage and children who never anticipated early retirement, figuring out how to balance their diagnosis with their job adds another layer of anxiety to an already dire situation.
"I would forget the patient I was seeing. I'd look at my notes and at the patient's chart and I wouldn't recognize my own handwriting. After the HIPAA [privacy] laws changed there was all this new paperwork and I just could not keep track," Thornton told ABC News from her home in Memphis.
After months of seeing doctors, one of whom suggested she was just a "stressed-out soccer mom," Thornton received her diagnosis from a physician who "couldn't have looked more unhappy that I didn't have a brain tumor."
Much of what causes dementia and how to best treat it remains unknown, including how best to handle a diagnosis in the workplace.
"Unfortunately, it is a situation where people don't know what to do," said Shelley Bluethmann, director of Early Stage Initiatives for the Alzheimer's Association.
"It is a gray area. The disease affects individuals in different ways. Someone might seem fine and not look sick, but be struggling terribly," she said.
"A patient cannot know whether a supervisor will understand or if there will be misunderstandings amid the other employees," Bluethmann said, adding that it was best for patients to be upfront about their diagnosis with their employer.
"In the workplace setting it is important to have open communication with the supervisor especially," she said.
Unanswered questions abound about whether early-onset patients are covered by laws to protect disabled workers from discrimination and if younger workers laid low by dementia are entitled to disability insurance through Social Security.
Generally, employers are encouraged to find work a disabled person can do to remain employed, but the law is not explicit about when and if someone with early onset dementia can be fired outright.
"The general standard is that employers should make reasonable accommodations for someone with a disability," said Janice Goodman, a labor lawyer who specializes in discrimination cases.
"But there are a number of factual issues that need to be considered. Can there be an accommodation for this person? It is different for a janitor than the president of a company," she said.
According to the Alzheimer's Association, early onset patients often lose their insurance coverage once they are unable to continue working. They are also often not yet eligible for Medicare or disability.
Earlier this month the Social Security Administration held hearings in Chicago to discuss expanding benefits for middle-aged people diagnosed with Alzheimer's disease and other forms of dementia.
"Individuals with early onset dementia can certainly apply for disability," said Mark Hinkle, a spokesman for the Social Security Administration. "We look at each case individually on a case-by-case basis. Whether or not someone will qualify will depend on the severity of their situation. We're working with the Alzheimer's Association on how to identify and help the most severe cases to get people the best care as soon as possible."
It is at work that many people first realize their diminishing mental capacity. Tasks that were once routine seem difficult and strange. Once-successful relationships with colleagues become strained when the diagnosed person struggles with his work.
Undiagnosed, Pat Van Dyke went through a series of demotions at a California-based sales company, unsure of why she had difficulty with tasks at which she once been proficient.
Over the course of several months, Van Dyke went from the executive assistant to the company's owner – managing several executive's schedules and regularly working with members of the staff -- to a receptionist, where she did little else but answer the phone.
"I started to make mistakes, I couldn't remember things, I couldn't do spreadsheets. I couldn't do anything without someone checking my work. No one wanted to work with me because I couldn't do anything. People assume you're not a good worker, that you don't care anymore, or that you're not trying," said Van Dyke, 55.
"I got a demotion and then I got another demotion. I tried to write things down, but I'd forget to look at my notes. My bosses were getting upset and the demoted me as low as they could," she said.
Once she received her diagnosis and learned she had early-onset Alzheimer's disease, she said her co-workers acted awkwardly around her.
"People don't understand what the disease is about. When you have cancer people are compassionate and understanding," Van Dyke said.
Van Dyke left her job nine months after receiving her diagnosis. She moved to Texas to live closer to one of her two adult children.
But for patients with young children, leaving work adds to the fear about how they will best be able to care for their kids.
"Often people are not financially prepared. The have dependents, sometimes they need money to pay for children who are ready to go college. Sometimes, in addition to caring for their kids they are also responsible for elderly parents," said Bluethmann from the Alzheimer's Association.
The association recommends young onset patients investigate early retirement and other financial planning options while still at work and make preparations with an attorney or financial planner.
For Diane Thornton, her diagnosis cut her family's income in half. Her children aged 14 and 17, she said, immediately felt the impact.
"We took a massive hit to our income. The kids stopped extracurriculars. We couldn't afford to pay for music lessons."
But, she says of her children, "they're incredibly resilient."
"We've been upfront about my diagnosis. They understand what is happening. I'm worried about them and they're worried about me. What scares me most is that I'll forget to keep worrying."