Dear Doctor: I enjoy a nice glass of wine at the end of the day, but I've heard various reports about its health risks. So, tell me: In women, does alcohol increase or decrease the chances of premature death?

Dear Reader: It depends on the amount. The most definitive study on this topic was done in 1995. It looked at more than 85,000 women, ages 34 to 59, and followed them for 12 years. That research found that having one drink (2 units of alcohol) every three to four days was linked to a significant decrease -- 17 percent -- in death during the course of the study. One drink per day was linked to an 11 percent decrease in death rates. However, more than one drink per day increased death rates, compared to no alcohol at all.

For women, the greatest benefits of alcohol were in the link to reductions of stroke and heart attacks. Yet, as women increase their alcohol intake, the risk of cancer increases. In this study, there was a significant correlation between having two or more drinks per day and breast cancer.

In short, alcohol does have benefits when it comes to lifespan, but those benefits vanish when a woman drinks two or more drinks per day.

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

Dear Doctor: I heard about a polio outbreak in Nigeria this summer. Might there be an outbreak here in the United States?

Dear Reader: Polio is a crippling, and sometimes fatal, infectious disease that was once common in the U.S. Caused by the polio virus, the disease was widespread among children. During the 1940s and '50s, outbreaks caused spinal and respiratory paralysis in 15,000 sufferers each year. With potentially dire outcomes and no cure, polio became one of the most feared childhood diseases in the United States.

That changed thanks to the development of the polio vaccine in the mid-1950s, and to the success of our ongoing national vaccination program. The Centers for Disease Control and Prevention states that polio has been eliminated in the U.S.

In our country, vaccination programs have resulted in a sharp decline in the number of polio cases, from 35,000 in 1953 to 5,300 four years later. With the introduction of an oral vaccine in 1961, the number of new cases acquired in the U.S. continued to plummet. There have been no new cases of polio reported in the U.S. since 1979. The last known case of polio acquired outside the U.S. and imported into the country was in 1993.

However, as you point out, polio remains a global concern. International health organizations have made polio vaccination a priority, with more than 2.5 billion children vaccinated worldwide since 1988. As a result, the overall number of new polio cases worldwide has dropped a remarkable 99 percent.

In 10 countries, however, including Afghanistan, Syria and Pakistan, vaccination programs have been difficult to implement and the disease continues to spread. And though Nigeria was declared polio-free in 2014, two new cases last August and a third case in September have raised the alarm. World health organizations are now redoubling their efforts to implement ongoing vaccination programs.

Is this polio epidemic a danger to the U.S.? The answer is no. Vaccination rates among adults are extremely high, and as long as parents continue to be vigilant about vaccinations and boosters for their children, we as a nation will remain immune to this terrible disease.

According to CDC guidelines, children should be vaccinated with inactivated polio vaccine (IPV) four times -- at 2 months of age, at 4 months of age, a dose between 6 and 18 months of age, and a booster dose between 4 and 6 years of age. Until this vaccination schedule is complete, children should not travel to an area where polio is still an active infection.

Eradicating polio worldwide has been one of the most remarkable and successful international health initiatives. Its ongoing success depends on each one of us continuing to be vigilant about vaccination.

(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: Will taking acetaminophen (Tylenol) during pregnancy increase the chances that the child will have ADHD or autism?

Dear Reader: Such concern is understandable. Parents and parents-to-be have been alarmed over the past few years by two Danish studies that raise the specter of greater ADHD and autism risks among children whose mothers took the over-the-counter pain killer acetaminophen during pregnancy. But let's look at these studies a little more closely.

The largest of these studies showed that, among children whose mothers ever used acetaminophen during pregnancy, 5.7 percent showed symptoms of hyperactivity by age 7. Among children whose mothers never took acetaminophen, 4.3 percent showed symptoms of hyperactivity. Similar mild differences were also noted for emotional problems and overall conduct.

Here's the important caveat: The two groups of women were themselves very different. Participants who used acetaminophen were more likely to be smokers, more likely to be obese (BMI greater than 30) and more likely to have had a fever. Just having a fever during pregnancy has been associated with autism, behavioral abnormalities and problems with attention.

As for the autism study, it linked acetaminophen use during pregnancy to an IQ drop of 2 points in 5–year-olds. Here, the cause of the acetaminophen use is an especially important factor. In this study, 37 percent of the mothers who used acetaminophen had fever; only 23 percent of those who didn't use acetaminophen had fever. And again, those who used acetaminophen were more likely to be smokers.

So one has to ask: Why does someone take acetaminophen during pregnancy? The answer: To reduce a fever. So fever may be the problem, not the acetaminophen. Further, women who smoke and are obese are more likely to be unhealthy during pregnancy, more likely to take acetaminophen for physical problems and more likely to have children who may also be less healthy.

Would I recommend acetaminophen regularly in pregnancy for joint pain and muscle aches? Probably not, though I would take it for a fever and for moderate pain. Otherwise, it's better to do prenatal yoga, gentle stretching and maintain a good diet.

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