Q: My mother, who lived to be 92, never caught my sniffles in her later years, even though I was her sole caretaker. And now that Im in my 60s, I notice that my colds are less severe. Is it possible to develop immunity to the common cold?
Possibly, to specific kinds of cold, said Dr. Jonathan L. Jacobs, professor of clinical medicine at New York-Presbyterian Hospital/Weill Cornell Medical Center.
The syndrome that we call the common cold can be caused by many different viruses, he said. After most viral infections, people develop immunity to that specific virus, which can last from a few years to a lifetime.
As immunity to different viruses builds up over time, it decreases the number of viral types that can make one sick, Jacobs said. But he added, There are so many viruses that cause colds that complete immunity is very unlikely.
As for the strength of symptoms of colds later in life, our genes, and the strength of the immune mechanisms that produce many of the symptoms that we associate with the common cold, are also important factors determining how sick we get when exposed to a cold virus, Jacobs said.
Q: Have any studies assessed the risks of hearing loss faced by people who ride the subway? Does it help to cover your ears?
A 2006 study of transit noise in New York City, measuring noise on buses as well as subway cars and platforms, was described as the first such formal study published since the 1930s.
The study by the Mailman School of Public Health at Columbia University, published in The Journal of Urban Health, found that noise levels at subway and bus stops could easily exceed recognized public health recommendations and had the potential to damage hearing, given sufficient exposure.
For example, guidelines from the Environmental Protection Agency and the World Health Organization set a limit of 45 minutes exposure to 85 decibels, the mean noise level measured on subway platforms.
And nearly 60 percent of the platform measurements exceeded that level.
The maximum noise levels inside subway cars were even higher than those on the platforms, with one-fifth exceeding 100 decibels and more than two-thirds exceeding 90 decibels.
The study recommended earplugs and earmuff-type protectors in loud transit environments, to cut noise at the eardrum.
It warned that personal listening devices only increased the risk.