Dear Doctor: I was recently diagnosed with an aortic thoracic aneurysm and scheduled for surgery. What are the risks, and can I expect to live a normal life afterward?

Dear Reader: As difficult as it is to hear the diagnosis of an aortic aneurysm, you're fortunate that your surgery could be scheduled. (More on that later.) Now an explainer for other readers: An aortic aneurysm is a bulging area within the aorta -- the body's main artery -- through which the heart pumps blood to the rest of the body. The aorta starts in the chest, called the thoracic region, and then runs down into the abdomen.

The problem with these bulges is that they can lead to rupture of the aorta, causing major blood loss and possible death. The majority of ruptures -- accounting for two-thirds of aneurysm-related hospital visits -- occur in the abdominal aorta; thoracic aneurysms account for the other third, and the rate is increasing.

People with thoracic aneurysms are usually unaware of the aneurysm until it is about to rupture; most are found through imaging studies looking for something else. The decision on whether to have surgery is based on the size of the aneurysm, whether the aneurysm is growing rapidly and whether it's causing symptoms. Survival rates are much higher for aneurysms that don't cause symptoms; the five-year survival rate in those needing urgent surgery is 37 percent, and 85 percent among people choosing to have the surgery. So you can see why the ability to schedule surgery is a positive.

The type of surgery depends on the location of the aneurysm. Those closer to the heart are more likely to require an open surgical procedure -- specifically, a median sternotomy. In this surgery, the sternum (breast bone) is cut up the middle to open up the chest, and blood must be bypassed away from the heart and into a machine that pushes it through the body. The diseased section of the aorta is then removed and replaced with an artificial graft.

For aneurysms farther from the heart, an endovascular repair can suffice. With this operation, there is no need to open up the chest. A doctor inserts a graft through an artery in the upper thigh and places it inside the vessel. The graft works like a stent, allowing blood to flow through it without putting pressure on the aneurysm.

The risks of an open procedure, because of the amount of surgery involved, are greater than those of endovascular repair. Complications include pneumonia, stroke and heart attacks during the procedure, although newer surgical techniques have dramatically lowered the complication rate.

One problem with the endovascular repair, however, is that over time -- in about 7 percent of cases -- the graft/stent within the blood vessel can move away from the area of the aneurysm, exposing the aneurysm again to rupture. Also, in 25 percent of cases, blood can leak around the stent (an endoleak), leading to increased risk of rupture.

Although the open procedure has a greater risk of complications, the overall survival rate is similar for both procedures. But surgical techniques for both procedures are improving all the time, increasing the likelihood of a return to normal life. I don't have the specifics of your case, but it's safe to say you should follow your doctor's advice to get back on your feet as quickly as possible.

(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: So many bad things seem to be associated with night shifts -- first an increased breast cancer risk, now an increased risk of obesity. Why is that? Is there any way to lessen the risks?

Dear Reader: You're right -- when it comes to the night shift, there's an ever-growing array of pretty bad outcomes. Research has linked this work schedule to a higher risk of coronary artery disease, a higher incidence of diabetes, and increased risk for several types of cancer, depression, social isolation and all manner of sleep disorders. Now, not that surprisingly, obesity has been added to the list. And although the ill effects of night shift work are diverse and wide-ranging, they all have something in common. That is, a significant and ongoing disruption of the body's innate time-keeping system -- circadian rhythms.

We humans have evolved to be awake and active during daylight, and to spend the dark hours in rest and sleep. During the 24(ish) hours that make up a circadian cycle, the shift from daylight to nighttime and back effects changes in our hormones, body temperature, brain function and other metabolic processes. Also involved are biological clocks -- sets of proteins that interact in cells throughout our bodies. These biological clocks are responsible for circadian rhythms -- and regulate their timing.

All of which is why, when a work schedule forces us to stay awake in the dark and sleep during daylight, it's not only our sleep cycles that get drastically altered. Eating habits, digestion, body temperature, the ebb and flow of hormones, and a host of other vital bodily functions are affected as well. Research has shown that the disruption to patterns of sleep and activity not only suppresses the production of melatonin, it may also affect the regulatory mechanisms of genes that play a role in the development of tumors.

It's possible for a worker to become accustomed to the night shift, but his or her body pays a steep price. And it's not just the traditional night shift that is bad for your health. Ongoing research shows that even a moderate deviation from the traditional 24-hour sleep/wake cycle, as in a swing shift or jobs that require rotating day and night hours, takes a physical toll. In the United States, this affects up to 25 percent of the populace, with the biggest challenge faced by workers whose schedules change week to week. Whether they compensate for those time shifts by powering through a sleepless stretch or by trying to switch to a morning bedtime, the outcome is akin to living in a constant state of jet lag.

For those who can manage it, getting into an unbroken 24-hour cycle for sleep and mealtimes can help, sleep experts say. Some workplaces understand the challenges of the night shift and will schedule workers for months at a time. The key is to control exposure to daylight, which regulates circadian rhythms. Be sure to spend time in bright light during a night shift. Wear sunglasses on the trip home from work. Use blackout curtains, sleep masks, ear plugs and sound machines in the bedroom. And on weekends, spend time with friends and family, but try to keep deviations from the schedule to a minimum.

(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: Much is said about calcium and vitamin D, but what about magnesium? As I understand it, that's a crucial part of the bone-building equation. Should people be taking magnesium supplements?

Dear Reader: The element magnesium is necessary for bone health, yes, but also for normal heart function and nerve conduction and to maintain a proper calcium balance in the body. Notably, although it's found in leafy vegetables, nuts, fish and shellfish, soy and cereals, magnesium levels in our foods appear to be slowly decreasing. One reason may be the overutilization of fields, leading to depletion of magnesium in the soil. A survey conducted in 1999 and 2000 found that 79 percent of American adults do not meet the recommended daily allowance for magnesium.

Magnesium, which is stored in the bone, is very similar in atomic structure to calcium, and deficiencies can lower the body's calcium levels. This happens in several ways. First, low levels of magnesium impair the release of parathyroid hormone (PTH), which raises calcium levels when they fall too low. Second, low magnesium levels actually block the function of PTH. And third, low levels decrease the formation of the active form of vitamin D, also needed for healthy bones. Further, low magnesium causes an inflammatory process in the bone, which leads to bone breakdown.

Animal studies show that rats fed magnesium-deficient diets, even in the short term, have more brittle and fragile bones than animals fed a normal diet. This happens because of decreased bone formation and increased bone breakdown. In humans, deficiencies can develop among people who don't absorb the element due to gastrointestinal disease, chemotherapy or alcoholism.

Accordingly, data from the well-known Framingham Heart Study found that people with higher dietary intake of magnesium had greater bone density. As for whether a magnesium supplement will help decrease the risk of osteoporosis, however, the data are definitely not conclusive.

Although a 2010 study found that postmenopausal women who took 1,830 milligrams of extra magnesium daily for 30 days had fewer markers for bone breakdown than those who didn't take extra magnesium, most studies assess the impact of only dietary magnesium.

A notable 2016 study combined data from 12 different studies (involving 109,564 people), assessing the risk of bone density and fracture in relation to magnesium intake. The authors found a slight increase in hip bone density among those with higher magnesium intake, but no increase in spinal bone density.

If you have a good dietary intake of magnesium and if you don't drink heavily or have intestinal or kidney disease, you're unlikely to benefit from taking a magnesium supplement. The best thing you can do for your bones is to eat a diet high in magnesium and calcium; get outside so your body can produce vitamin D; and exercise.

(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.)