Dear Doctor: My father passed away six months ago, and ever since, my elderly mother has withdrawn from all social activity. I can't help wondering if this poses a problem for her mental health.

Dear Reader: The loss of a loved one is a heavy burden for anyone to bear. For an elderly person, particularly a surviving spouse, it can be even more difficult. Elderly women and men are already dealing with challenges such as declining health, loss of independence and the shrinking of their longtime social circles. When faced with the loss of their life partner, the overwhelming grief can cause them to retreat.

Your concern for your mother is well-founded. Research shows that social isolation poses a real threat not just to her cognitive function, but to her physical health as well.

Elderly people who are socially withdrawn are at greater risk of long-term illness, high blood pressure, heart disease, dementia, losing their ability to walk and stay mobile, and of serious depression. Grief can suppress the immune system, making the elderly even more vulnerable.

Studies reveal that elderly men and women who do not engage with other people die at a significantly higher rate than those who remain socially connected. This is a particularly troubling statistic as the number of senior citizens who live alone is on the rise.

Fortunately, there are steps you can take to help:

-- Research shows that grief counseling can help surviving spouses manage their sense of loss. Encourage your mother so see a counselor, or find a support group that she can join.

-- Something as simple as making transportation easily available can help isolated seniors break free of their bubble.

-- If your mother has connections to a church or other spiritual community, reviving those ties can be helpful at this time.

-- Gathering family members at your mother's home for a meal or a movie can brighten her day. Make it a weekly or monthly habit if you can.

-- For seniors who are strong enough, volunteer work, particularly with young people, gives them a meaningful activity that often has a positive effect.

-- Encourage your mother to establish a new daily routine. A sense of stability can help life to feel normal again.

You may be so concerned about your mother's pain that you are shielding her from your own. Don't be afraid to let her see the sorrow you feel about your father's passing. Grieving together -- sharing memories, telling stories, simply stating how you feel -- can bring you closer and help her to feel ready to join the world again.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)

Dear Doctor: I'm a 45-year-old man. Do I really need a PSA test every year?

Dear Reader: The short answer: Only in certain situations. Prostate cancer is the second-leading cause of cancer death among men, and in an effort to spot it early, doctors have long used the PSA test to measure prostate-specific antigen, or PSA, a glycoprotein produced within the prostate. PSA production increases in prostate cancer, as does the release of the protein into the bloodstream.

Since the inception of the PSA test in 1986, prostate cancer diagnoses have increased so much that one in six men will now be diagnosed with prostate cancer in their lifetimes. One might think it is a good test, but not so fast.

The PSA test is problematic in three ways. The first is that it will detect many prostate cancers that will never be clinically significant, meaning they will never cause symptoms. Autopsy studies have shown that 30 percent of men have some form of prostate cancer by age 55, and 60 percent of men have prostate cancer by the age of 80. The majority of these cancers would have gone unnoticed, with no ill effects.

The second problem with the test is that investigating an elevated PSA with a prostate biopsy can cause significant side effects, including prostate infections, impotence, incontinence and, occasionally, death. These side effects are magnified when a patient has either prostate surgery or radiation treatment for prostate cancer, a type of treatment that may be unnecessary for a low-grade prostate cancer.

The third problem with the test is that PSA levels also increase in men who have enlarged prostates or inflamed prostates -- but not cancer. Men can be subjected to biopsies and their inherent risks simply because they have another condition entirely.

Based on these problems, some professional organizations now recommend that doctors not perform the PSA test. What appears to counter this logic is a large European study with 162,243 men ages 55 to 69 that showed the prostate cancer death rate decreased by 21 percent in men who were offered a PSA test every four years.

The American Urological Association (AUA) has taken this study into account and varied its recommendations by age and risk. It does not recommend screening for average-risk men between the ages of 40 to 54, but says that higher-risk men -- typically those with a family history of prostate cancer or who are African-American -- may benefit at that age.

For men ages 55 to 69, the association recommends that doctors explain the risks and benefits of the PSA test and conduct it every two years. This recommendation changes for men with an elevated PSA, between 4 and 7. In these men, testing should be more frequent to make sure that the level does not rise beyond 7, which may be an indication for biopsy. However, if the PSA level is consistently low and at a level of 1 or less by the age of 60, there may be no need for further screening tests.

So my feeling is that the PSA is a useful test for average-risk men between the ages of 55 to 69, but it doesn't have to be repeated yearly if it is normal. The test could be done every two to four years.

Another variable that may add to decision-making -- and take some of the fear out of the follow-up -- is the advent of the prostate MRI, which can both detect prostate cancers in men with an elevated PSA and decrease the complications from prostate biopsy. That technology suggests that the pros and cons of the PSA will continue to evolve.

(Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.)

Dear Doctor: I read that sugar might be worse for your heart than fat. Should I give up sweets?

Dear Reader: If you're one of the millions of Americans with a sweet tooth, there's some good news. According to current guidelines from the American Heart Association, eating a modest amount of added sugar each day -- six teaspoons for women, nine teaspoons for men -- is safe for your heart.

But before you pop open the cookie jar (or that pint of Ben and Jerry's), let's review some hard facts. Research shows that eating too much sugar can significantly increase your risk of heart disease. Individuals who received between 17 and 21 percent of their total daily calories from added sugar had a 38 percent greater chance of dying from heart disease compared to people who limited added sugar to 8 percent of their total daily calories.

That study, published in the Journal of the American Medical Association in 2014, had even more sobering news. People who got more than 21 percent of their daily calories from added sugar doubled their risk of heart disease. Considering that the average American now eats up to 20 teaspoons of sugar per day, we've got a problem.

Although saturated fat has received the lion's share of blame for heart disease in the United States for many years, sugar is now taking center stage. Studies show that sugar leads to potentially harmful changes in levels of blood cholesterol and triglycerides, both markers of heart disease. Diets high in added sugar have been tied to other abnormalities associated with heart disease, such as high blood glucose levels, decreased glucose tolerance, insulin resistance and fatty liver disease.

While the occasional sugar splurge is probably not a problem, keeping daily consumption to a minimum is vital to heart health. Which brings us back to that recommended maximum of six (or nine, if you're a man) added teaspoons of sugar per day.

It may sound like a lot, but consider this -- the average 12-ounce can of soda has about 10 teaspoons of sugar. And with the stealthy addition of sugar to products like breads, canned vegetables, pasta and barbecue sauces, staying within guidelines takes vigilance.

Still, it's worth it. A recent study showed that when a group of obese children reduced added sugar from their diets, it took just nine days for their triglyceride levels -- a marker of heart disease -- to drop by one-third.

So, an apple or an Oreo for your afternoon snack? Not really a difficult choice.

(Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.)