Dear Doctor: Can you shed some light on transient global amnesia? I was diagnosed with this five years ago (I'm now 71) after my family noticed that I couldn't recall common facts. I had no physical ailment or injury prior to this, and I'm told that the recurrence rate is 1 percent.

Dear Reader: Transient global amnesia is, as the name describes, a short-lived inability to retain new memories. Because the episodes are so sudden, they can be disorienting to all involved. Afflicted people often repeatedly ask questions about the date, their location or their reason for being there. They can temporarily lose memories from a few hours before the event to, more rarely, up to a year before the event.

Note that such episodes do not affect a person's ability to perform complex tasks such as driving, cooking, lecturing and playing a musical instrument. Nor do the events interfere with self-awareness.

The episodes last, on average, about six hours, but can be as short as one hour or as long as 10 hours. Afterward, a person does not remember anything that transpired during the episode and may even lose some memories formed just before the incident. Although the episodes can be preceded by an acute emotional event, physical activity, or exposure to cold or heat, doctors don't really know what causes such amnesia.

MRIs have shown that the events affect the memory centers of the brain in the temporal lobe and in the hippocampus. Like the symptoms, however, the resulting lesions that develop in these areas are not permanent. Some brain experts suspect that blood flow restriction may be a trigger, but the evidence for this is thin. Another hypothesis, which has more merit, is that a backflow of venous blood is the catalyst; such flows are more likely to affect the aforementioned parts of the brain.

One strong risk factor is psychogenic stress -- in other words, a psychiatric condition that produces a physical response. A 2005 study found that people with a history of psychiatric disease or alcohol abuse had three times the likelihood of experiencing transient global amnesia.

The condition typically occurs in people ages 50 to 80 and is diagnosed in one in every 3,500 people over 50 each year in the United States. The peak incidence occurs in those 60 to 65. Men and women are equally affected. Because the symptoms can resemble those of a stroke or a transient ischemic attack, many people mistake the condition for a stroke or TIA. Unlike those conditions, however, transient global amnesia doesn't have a vascular cause, and people who experience it have the same incidence of stroke as the general population. Nonetheless, because of the similarity in symptoms, immediate medical attention is needed to rule out more serious causes.

You mention a 1 percent recurrence rate, but studies have shown the rate to be about 5 percent. This is still very low.

This sudden loss of memory must have been unnerving for you. Please take some comfort in the fact that it's unlikely to happen again.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I never gained the infamous "freshman 15" while I was in college. But now I've graduated and am behind a desk for nine hours a day for my new job. I'm not only putting on the pounds, I feel generally lousy. Is this just adjusting to working life, or is sitting so much bad for you?

Dear Reader: Making the switch from the freeform life of a college student to the strictures and structure of a full-time job can indeed be a challenge. It's quite possible that some of what you're feeling is a result of this shift in lifestyle. However, your question zeros in on an important element of the modern workplace, and one that numerous studies have identified as a genuine health hazard. That is, the fact that so many of us spend the majority of our days sitting. To quote more than a few of the headlines we've seen on the topic -- sitting may be the new smoking.

Our bodies are built for movement. Every one of our systems -- lungs, circulatory, lymphatic, skeletal and muscular -- benefits from regular activity. Even improved mood and memory have been linked to physical fitness. Yet the default of our modern world has become inactivity, whether it's in cars, at desks, on couches or seated in front of screens. As more and more of us began to spend our lives sitting down, researchers examined the consequences. The results have been anything but reassuring. Numerous studies have now linked those long hours of sitting to an increased risk of a number of health threats, including diabetes, some cancers and heart disease.

An intriguing new study from the University of Illinois-Chicago suggests a new way forward for desk-based workers. Researchers evaluated the merits of three different types of work stations. One was the desk-and-chair combo we're all too familiar with. One was the standing desk, which has become a common sight in many workplaces. And one was a seated desk that had been outfitted with a mobile foot rest. The device, which goes by the brand name HOVR, is basically a leg swing that allows the seated person to stay in motion.

According to the study, individuals who used the mobile foot rest burned 17 percent more calories than did those who sat still. Interestingly, the foot rest group also used 7 percent more calories than people at standing desks. Admittedly, it's a modest step forward (sorry), but the point we took from the study is that even small interventions can be beneficial.

Whether the option of a foot swing is in your future, you can make some changes to how you spend your work day. Stand up and stretch every 10 or 15 minutes. Take short walks around the office. As much as possible, add motions that flex and stretch your legs, arms and trunk muscles. And it wouldn't hurt to ask whether your workplace offers any alternatives to the seated desk.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My ex-wife was seeing a primary care doctor who also treated her heart issues, which were not of a serious nature. She sought a second opinion from a specialist, which prompted her own doctor to unceremoniously drop her as a patient, without even informing her. She found out the next time she called for an appointment. Is this ethical -- or even legal?

Dear Reader: One of the most satisfying elements of a physician's job is helping a patient. That sense of satisfaction, along with the respect for the profession and praise from our patients, can infuse a physician's sense of self-worth, potentially inflating the ego of even the most humble physician. Conversely, when a patient is unhappy with a doctor or when a doctor's diagnosis proves to be incorrect, a physician can question his or her ability and value. And, of course, doctors -- like everyone else -- have biases, personality quirks, stressful days and distractions caused by many nonwork factors. In short, doctors are people too.

I don't know whether your ex-wife and her primary care doctor had a good, long relationship or a short one marked by poor communication. But a strong primary care relationship is essential to overall high-quality medical care. A primary care doctor is the physician you see for physicals, and the first doctor you see for colds, injuries and many other maladies. Because of this, such physicians often have a deeper understanding of the whole patient than would a short-term specialist, and they take that position seriously. When a patient seeks a new primary care doctor, or seeks the advice of a specialist without the other doctor's knowledge, the doctor might feel that his or her care was considered inadequate.

When that happens, some doctors may feel that it's an attack upon their self-worth and will act in a defensive way. Others are more deferential, realizing that they can't help or please everybody. These doctors don't feel threatened by opinions from other physicians.

Obviously, I don't know what transpired in the mind of your ex-wife's primary care doctor -- and I'm not defending his or her actions. A conversation that sought to identify any potential concerns on her part would have been a better way of handling the perceived slight. That said, a doctor has every right to fire a patient for not following recommendations, rude behavior or missing multiple appointments.

As for the legality of the doctor's actions, laws in many states penalize doctors who abandon patients needing specific medical care. That means if a patient is in a medical crisis, it is incumbent upon the doctor to either take care of the patient or find an immediate alternate provider. In writing a discharge letter from a practice, a doctor usually gives a 30-day window, giving the patient time to find a new doctor and obtain medication refills. Clearly, the doctor should have provided a warning letter or a letter of discharge.

The relationship between doctor and patient is fraught with the difficulties of human interaction. A poor relationship with a primary care doctor can lead to bad outcomes, regardless of who is primarily at fault. Dissolving the relationship under these circumstances may be for the best.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)