Dear Doctors: Can you please explain about masks again? Why do we need them, what kind should we wear, and what is the proper way to wear them? It would really help me to explain to my friends and family so they can be safer.

Dear Reader: We continue to get letters from all parts of the country asking these same questions. We’ve written about masks before, but new information often takes repetition to sink in. It also takes time for new habits to take hold. We’re happy to do a recap for those of you who are still unsure about the why and how of using a mask during the COVID-19 pandemic.

Now that we have learned so much more about how this particular coronavirus spreads, wearing a mask turns out to be a crucial part of protecting our families and communities. The bottom line is that you wear a mask to keep your breath to yourself. Research shows that the main way this virus travels is via the droplets and aerosols we emit when we sneeze, cough, speak and sing, and even when we breathe. When you wear a mask, you create a barrier that catches some of these particles and limits the distance your breath can travel. Combine that with the 6-foot buffer zone we have come to know as social distancing, and the odds of transmission are significantly reduced.

Even if you’re not worried about the coronavirus on your own behalf, you can be sure that there are vulnerable people all around you. This one simple habit -- which, let’s face it, isn’t a real burden for the majority of us -- can literally save a life. In fact, the life you save may be your own. The latest research shows that a good mask, worn properly, can also help to protect the person who is wearing it.

A mask works by providing a network of fibers that both slow the force of an exhale and capture respiratory droplets. The closer the weave, the more effective the filtering effect of the mask. Tightly woven cotton masks with multiple layers are more efficient than looser fabrics, such as a scarf or a bandanna. The nonwoven materials of the N-95 masks are the most effective. Shape and fit also play an important role. A good mask has a snug but comfortable fit without any gaps around the perimeter. It fits over the nose and under the chin, and it leaves enough space around the nose and mouth for easier breathing. Masks with valves don’t slow or trap any aerosols and, therefore, do not protect the people around you.

When you breathe out through a mask, the fibers capture many of the droplets you generate. The rest travel a much shorter distance than they would in a maskless exhale. When someone wearing a mask exhales near you, the load of aerosols headed your way is reduced. If they do reach you, your own mask filters them, again reducing the number of particles that reach you. When everyone wears a mask, we’re working together to reduce one another's level of risk.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: Why do the elderly lose ground mentally when they go to the hospital? Our grandmother had emergency gall bladder surgery, and afterward she got so confused that she thought our grandfather, who passed away, was in the next room. It lasted for a few days, and it was scary.

Dear Reader: Although we can’t know the exact nature of your grandmother’s cognitive lapse, the type of confusion you describe isn’t unusual in older adults who have been hospitalized. Sometimes referred to as hospital-acquired delirium, it’s a temporary but severe form of mental impairment that affects up to one-third of patients over the age of 70, particularly those undergoing surgery or those in intensive care. The condition is marked by periods of confused thinking, jumbled memory, difficulty understanding speech, agitation, disorientation and even hallucinations.

These episodes of delirium are often interspersed with interludes during which the person is once again lucid. The duration of hospital-acquired delirium can be as brief as a few hours or, as with your grandmother, can continue for several days. In some cases, these fluctuations in awareness can last much longer. In addition to being upsetting to family members, the condition can hinder the patient’s recovery and lead to a general decline in health.

When you consider the many shocks involved with surgery and hospitalization, it’s not surprising that the experience can take a steep mental toll on older adults. Not only has the body endured the physical trauma of a surgical procedure, but the patient is also dealing with the effects of anesthesia and the drugs used to manage pain. Once the patient awakens, the hallmarks of their everyday lives have suddenly vanished. They find themselves isolated in a strange place, being cared for by an ever-changing array of strangers. The bright lights, constant noise, ongoing medical interventions and frequent interruptions of hospital life create a stressful environment. Adding to the burden are factors such as infection, dehydration, poor nutrition, anxiety, poor sleep and the potential side effects of multiple medications.

Treatment begins with basic care. That means making sure the person is hydrated, is getting enough nutrients and adequate sleep, and is warm, dry and comfortable. It’s also important to help them become oriented to their surroundings. This may sound obvious, but it includes making sure that they have and use personal items such as their eyeglasses, hearing aids or dentures. Each of these help to engage their senses, which lets them stay aware of the world around them.

Other things that have proven helpful are daily exercise, exposure to natural light, removing medications that are not absolutely essential and surrounding the person with familiar objects from their home life. A favorite sweater, a stuffed animal or an array of family photographs can provide visual and sensory cues. Music, which boosts brain activity, has been shown to relieve stress and anxiety.

And if the hospital allows visitors, try to go to spend time with your loved one. Patients feel vulnerable and alone in a hospital setting, and having a familiar and loving presence nearby offers great comfort.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: Our family spends a lot of time these days on our screens. I’ve always had trouble sleeping (mom brain), but now my husband and our two teen boys are struggling, too. Do you think all the screen time could be why?

Dear Reader: We’re all dealing with so much right now -- stress, anxiety, isolation and uncertainty -- that poor sleep has evolved into an epidemic of its own. And with a large portion of our daily lives taking place online, it’s quite possible that the high-energy light emitted by our computers, tablets and smartphones is adding to the toll.

For many of us, the work day, the school day and even socializing have shifted online. Add to that the hours we were already spending on our screens before the pandemic, and many of us are getting the highest daily doses yet of what’s known as “blue light.”

Similar to sunlight, blue light has been shown to suppress the release of melatonin, a hormone produced by the pineal gland in the brain that makes you feel sleepy. Recent studies have found that prolonged exposure to blue light, particularly in the hours before bed, confuses the brain. Instead of the warm tones of evening light, which signal the brain to power down and prepare for sleep, the blue light emitted by electronic devices insists it’s daytime.

This affects not only the ability to fall asleep, but also to stay asleep and spend adequate time in the various stages of sleep -- especially the all-important deep sleep. That’s a serious problem, because lack of high-quality sleep not only leaves us tired in the short term, it also is associated, over time, with more serious health issues. These include headaches, weight gain, diabetes, high blood pressure, coronary heart disease and depression.

The good news is that you can take specific steps to mitigate the effects of exposure to blue light and improve your ability to fall asleep and stay asleep. One cornerstone of good sleep hygiene is a consistent bedtime. Decide on what your bedtime will be, then end all screen use at least two hours -- and preferably three hours -- before then. If you don’t build in that no-screen buffer, the blue light will continue to tell your brain that it’s broad daylight. This, in turn, confuses your inner clock, which throws off your ability to fall asleep.

In that same vein, block the various digital lights that can populate the bedroom, such as clock dials, smoke alarms and other electronic devices. When it comes to working with a computer or tablet, consider purchasing special filters, which reduce the amount of blue light that a device emits. Protective eyewear that blocks blue light is also available.

Quite a few manufacturers now include a special “night mode” option for smartphones, computers and tablets. When activated, night mode shifts the light emitted by the screen from the high-energy blue light to the warmer end of the spectrum. This all takes planning and discipline, but, considering the stakes, it’s worth it.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)