The thick metal door at the clinical center at the National Institutes of Health (NIH) buzzed shut, locking me in, just it had my dad several years ago. Once a year for the last three years of his life, he registered this sound with dread. Now, it is my turn -- with one difference. For me, the buzz represents my best hope.

When my father was diagnosed with Alzheimer's disease in the early 1990s, he decided to volunteer for a research program at NIH aimed at finding possible causes of the disease. If he didn't find a cure for himself, he figured, at least he might help others. "I don't just want to sit here turning into a vegetable," he said. "I know what is going to happen."

The knowledge came firsthand. He'd watched his grandmother die of the disease in 1944, his mother 40 years later. He would die of it himself in 1999. His sister, who also volunteers in the NIH program, was recently diagnosed at age 77.

I have no symptoms of Alzheimer's, but I am 52. The doctors at the Alzheimer's Family Study have invited me to participate in a longitudinal study; the volunteers -- 250 are now enrolled, recruited from across the country -- return annually for retesting. They include people with memory disorders, people like me with a family history of the disease and some who have neither symptoms nor a family history.

Why spend three days in this Bethesda high rise? For one thing, there are the personal benefits: an amazingly thorough physical for free and the chance to put yourself in line for experimental therapies. There's also the idea that you might help find a cure to an ailment that's replacing cancer and heart disease as the old-age illness many families fear most.

Alzheimer's, the most common form of dementia, affects at least 2 million people in the United States. The disease proceeds over years to gradually snuff out the brain's operations. You begin to forget words, lose the ability to reason -- and eventually to carry out even the most simple tasks.

"Most people volunteer here because they have been personally impacted by . . . Alzheimer's," said my nurse practitioner, Irene Dustin. "How do you put a price on that?"

I have been in denial about my chances of getting this disease. NIH asked me to participate several years ago, but I thought I was too young to worry. Doctors say they cannot calculate who will get it and who will not, although they agree a family history of it certainly increases the risk. All my life, my mother would joke, "You think just like your father!" The teasing comment I used to be so proud of now rattles me a bit.

I remember when Grammy, that proper lady from Cornwall, England, began in the 1970s to change her clothes 12 times a day, to talk to refrigerators and look at me with stark, helpless fear. And as I look back at my wedding pictures from 1990, I see Dad staring into space with an odd slack downturn of his usual smile. Mom said he was just emotional about the wedding. I know better now.

Ham and Eggs

Doctors told me that for the Alzheimer's study, I would undergo cognitive tests and physical tests, such as an MRI of my head and a lumbar puncture, more commonly known as a spinal tap. I would also conduct a household task while an occupational therapist took notes. This exercise is done to track the participants' motor and mental skills.

My father's task every year was to make a ham sandwich in a stocked kitchen. We always joked that he never made anything in the kitchen at home; how the heck would he do there? Actually, he made quite a fine sandwich the first year. By his last year, though, he would open and close cupboards again and again, sure he was supposed to find the answer behind them -- somewhere.

"It is very sad for me to watch the changes," said Fran Oakley, the occupational therapist in charge of the kitchen. "But it is nothing like it must be for the family."

This fall, I decided it was time for me to find some answers,so I agreed to sign up for the study. The night before I was to check in, I anguished over how many novels to bring. Would there be shampoo? Could I jam that terry-cloth bathrobe into the suitcase? Was I perhaps focusing on these details as a form of diversion?

The center was an easy walk from the Red Line. Once through security, I signed consent forms and had a plastic ID bracelet snapped on my wrist.

Then I approached the locked door of the Alzheimer's ward. Dad had hated that door. The whole family hated it. Alzheimer's patients often wander, so locking them in is necessary. But Dad never understood that. As the disease progressed, he'd bang the door to leave with us when our visits were over, peering through the small glass window with increasingly clouded eyes.

I was buzzed in and shown my room. As I sat on the edge of a thin mattress, a nurse and a nurse practitioner explained what would happen over the next three days.

Then the tests began. I gave numerous tubes of blood. They will be tested and analyzed, and some frozen for future use. There was also the spinal tap. While you hunch over a chair, the doctor uses a needle to withdraw about a tablespoon of spinal fluid. That fluid, I am told, offers a chance to find markers for what is happening in the brain. The procedure is not as gory as it sounds; the siphoned fluid is replaced by the body within two hours.

Doctors study both the blood and the spinal fluid to rule out any abnormalities. Because there is no way yet to diagnose Alzheimer's definitively while a patient is alive, the clinical diagnosis is referred to as a diagnosis by exclusion: Rule out other disorders first. They also look for disease markers -- among them proteins called beta-amyloids that build up in the brains of Alzheimer's disease patients -- and other common patterns in study patients.

For my household task, I was assigned to make scrambled eggs spiced with diced onions and cheese. I cook every day, but now a therapist was watching my every move, constantly scratching in her notebook. Was I doing okay?

Then, there were numerous cognitive tests, some relatively simple: Who is the president? Tell me the three words I mentioned 10 minutes ago. Where are you now? Then, more complicated ones: Count backward from 100 by sixes. If the red dot flashes in the same spot as the black dot did a moment ago, press "same." Read the math problems out loud, then say if the answer is correct or not, and say the word after the problem. After four to eight of these, we will ask you to write down the words in the correct order.

Arggghhh.

Brain Games

I sat at the edge of my seat, determined to get an "A", to show my mind was not only smoothly running but maybe bordering on genius. These tests were challenging. How, I asked psychologist Ginny Rosen, could a person with Alzheimer's possibly take these tests? They do not get all the same tests, and they do get frustrated, she said, "but you would be touched at how hard they try." The best cognitive testers are college-aged.Their brains are agile, and they are used to absorbing and memorizing many diverse facts. "I want to tell them to enjoy it now," said Rosen, "because this is as good as it gets."

The staff was comforting and professional. Some remembered my father. Even though he threw his pills on occasion, and even popped a nurse once, they remember the true Dad, a gentleman with a fine dry wit. As a former CEO, Dad was most comfortable making decisions -- okay, giving orders. As he spiraled deeper into the miasma of Alzheimer's, the staff let him sit in on their daily meetings. He was sure he was running them; they accepted that.

There is a special knack to working with Alzheimer's patients: Treat them with respect and dignity. They may be confused, but they recognize fear or patronizing behavior.

The staff also helped my mother learn how to help Dad through the stages of the disease.

There were some mishaps during my visit to NIH: The lumbar puncture proved difficult because of a previous injury to my back. Also, some kind of electrical surge caused dust to burst from the vents at 1:30 a.m. the first night. As a precaution, we were evacuated to the floor for patients with bipolar disorders. My new roommate was very nice, but she talked much of the night. How am I going to remember more red dot tests and math problems on three hours of sleep, I wearily wondered.

Between tests, in the living room and dining area, I met several volunteers who were in the early stages of Alzheimer's. Some were attached much of the day to rolling racks of fluids. Others were there to be assessed.

One man, from the Virgin Islands, brought reggae music and picture books of the islands. A second, a 65-year-old from Colorado, relayed what he called his Greek tragedy: He had been his mother's caretaker as she struggled with Alzheimer's. More recently, a week before he was to marry for the second time, he and his bride called off the wedding because they began to suspect he also had Alzheimer's. "I don't wish [the caretaker role] on anyone," he told me.

What They Won't Say

A certain gene, ApoE or apolioprotein E, may play a role in determining who gets Alzheimer's and who doesn't. But because doctors are not sure of that role, I would not be told whether I had the gene or not. "You can have the gene and not get Alzheimer's," Trey Sunderland, the doctor in charge of the family study, told me. "You can not have the gene and get it."

I pushed a bit. If I do get Alzheimer's, it will be for genetic reasons, I said. I'm here for information-gathering purposes. Tell me.

What would you do differently if you knew? asked Sunderland. You are indeed at a higher risk because of your family history, he said. If I were you, he continued, I would take 1,000 milligrams of vitamin E daily, take estrogen. Sign a living will, think about long-term care insurance.

This probably was the lowest moment of my visit. Long-term care insurance? These people really think I might get this disease!

I must have done adequately on the tests. Staff members do not relay scores, but they do tell you if you are "normal," or if you are showing early signs of Alzheimer's. I'm still normal. But I will be back next year. I also have signed up for an auxiliary study, where I take a medication -- a cholesterol-lowering statin drug or anti-inflammatory ibuprofen, I won't know which -- for three months, then have that lumbar puncture again to see if any of the disease markers have changed. Research suggests one of these might help delay the progress of Alzheimer's.

I wish I did not have to worry about this. I'd prefer to simply focus on regular exercise, moderate wine intake and healthy eating to aim for a long retirement. My mother had left me a note earlier, expressing admiration for how brave I was to volunteer. I'm not brave, I'm scared. It's all the more real now, after my three-day visit. But I thank my father for setting the example of not taking this disease lying down.

My last day, I packed the bathrobe, which I used a lot, and the novels, which I did not. For a final time during this visit, I was buzzed through the door and returned to the outside world.

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Barbara Geehan is a freelance writer in Alexandria.