Dear Doctor: I am a senior citizen on Medicare. I don't have a "regular" doctor, but rather, I go to a clinic when I have a problem. What is covered in the annual Medicare physical? What should I, as a patient, know and do?

Dear Reader: Let's face it -- health insurance can be complicated and confusing, and Medicare is no different. We hope we can offer a bit of clarity regarding Medicare's annual physical exams, the details of which often leave our own senior patients with plenty of questions.

In the 12 months after you enroll in Medicare Part B, you're eligible for something known as a "preventive care" visit. During this appointment, you'll tell your doctor your personal medical history as well as your family history. She or he will record your height, weight and blood pressure, and will calculate your BMI, or body mass index. You'll get a vision test, and you'll be evaluated for risk of depression and any other potential safety issues.

Certain screening tests and vaccinations may be ordered at this time. Because details vary depending on each specific case, be sure to ask your doctor whether additional costs will be incurred. You may have to pay coinsurance, and the Medicare Part B deductible may apply.

During this initial visit, you'll also have a chance to discuss advanced health directives, sometimes known as a living will. You will receive a written plan that details a future schedule of screenings, vaccines and any other preventive services your medical history has indicated may be necessary.

Each subsequent year, Medicare entitles you to an annual physical evaluation that is less comprehensive than what we think of as a full physical. Known as a yearly wellness exam, it focuses on what a physician can see, hear and feel during an exam, such as heart rate, blood pressure, weight, BMI, heart and lung sounds and visible symptoms. However, the wellness exam does not include blood tests like complete blood count, kidney, liver and thyroid function, diabetes and cholesterol screenings, or a check of vitamin D levels, which we include in annual physical exams in our practices. These can be ordered, but depending on the test, there can be additional costs.

To get the most out of any physical exam, we recommend that patients bring the following:

-- Complete medical records, including immunization records, results of recent screening tests and information on any surgeries.

-- A list of all medications and supplements you are currently taking, including dosage, history of use and any side effects you may have experienced.

-- Comprehensive medical family history, including diseases like cancer, asthma, diabetes, memory disorders or dementia.

This last part is important because if your doctor determines that you are at particular risk of a certain disease or condition, you may be eligible for additional screenings and more frequent screenings. However, this typically requires a referral.

Lastly, we would encourage you to find and build a relationship with a primary care physician. This will give you a medical "home base," a doctor who knows you and your medical needs, as well as a partner in your ongoing care and an advocate for your best quality of life.

(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.)

Hello, dear readers! We hope that you're settling into 2018. (It still sounds odd to say it!) We love that you're keeping our inbox full, and, as ever, we remain grateful for your interest and engagement in our columns.

Quite a few of your letters delve deeper into topics we have tackled and are slated to become the subjects of follow-up columns. To those who have written to thank us, we say thank you. And now, onward, as we address a few of your questions, thoughts and concerns.

-- A recent column about headaches and their causes prompted a reader from Madison, Wisconsin, to write in with an addition to the list:

"There is one more possibility that is often ignored," she wrote. "My son had headaches on and off between the ages of 12 and 17. At age 17, he had his wisdom teeth out, and the headaches were gone. People with headaches that start in their teens may want to check with a dentist to see if their wisdom teeth are impacted."

While not nearly as common as the causes discussed in the column, impacted wisdom teeth can trigger painful and repeated headaches in some people. These teeth, which are the third molars at the back of the mouth, often lack adequate room to emerge. Whether due to infection, pressure or misalignment of the jaw, the result can be recurring headaches. If the onset (or increase) in headaches coincides with the typical age range for wisdom tooth eruption -- 17 to 24 -- it's a good idea to check with your dentist.

-- The dental angle on headaches got a thumbs-up from another reader, who says she was initially a skeptic:

"The 'dental problem' was a cause that I didn't buy into," she wrote. "My dentist told me I was grinding my teeth, and though he made me a tooth guard, I didn't wear it for years. I finally gave it a try because my headaches persisted and pain meds were hurting my stomach. No more daily headaches!"

-- We loved this story from a reader from Naples, Florida, in response to our column about the importance of the annual physical exam.

"A friend of mine, who was feeling fine, went to her annual physical," she wrote. "Routine blood tests revealed that she had leukemia. She immediately sought treatment and today, 20 years later, she's fine. I can't think of a more powerful argument in favor of having an annual physical."

Needless to say, we heartily agree that an annual physical exam can be a lifesaver. Whether it's identifying "silent" problems like hypertension or the early stages of serious illness, or enlisting your primary care physician as your partner in long-term health and wellness goals, a yearly physical is a powerful -- and empowering -- tool.

-- Finally, we just learned of an interesting advance in cochlear implants, which we addressed in a column recently. New programming software that was just approved by the FDA will allow audiologists to evaluate and adjust a patient's implants from afar via remote programming software.

(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: Because I have fair skin and live in an area with a lot of sun, I try to do my outdoor activities early in the day (before 9 a.m.) or late in the afternoon (after 4 p.m.). Do I still need to wear sunscreen?

Dear Reader: In a word, yes. If your goal is to protect your skin from sun damage, which includes sunburn, wrinkles and a range of cancers, our advice is to wear sunscreen during the daylight hours. In fact, research now shows that even a light tan is a sign of sun damage.

This dawn-to-dusk timing for sunscreen application may seem counterintuitive; after all, sunlight looks and feels markedly weaker during the early morning and late afternoon than at midday. While it's true that the sun's rays are strongest between 10 a.m. and 4 p.m., the fact is that from the moment it appears above the horizon to the instant it vanishes from sight, our closest star is sending a full dose of skin-damaging ultraviolet radiation our way.

How can that be?

Sun damage is caused by two types of radiation -- ultraviolet A and B, better known as UVA and UVB. These are part of a broad spectrum of light, which includes the light we can see. But because ultraviolet rays are shorter than rays of visible light, they can't be seen with the naked eye. However, what you can't see definitely can hurt you.

The so-called "sunburn ray" is UVB. It has a slightly shorter wavelength than UVA, and is not as concentrated in the early morning and late afternoon. The highest amounts of UVB radiation reach us between 10 a.m. and 4 p.m. in the months of April through October. And while UVB accounts for only 5 to 10 percent of all UV radiation that reaches us, it plays a key part in the onset of skin cancer.

By contrast, UVA maintains the same intensity all day, which makes dawn-to-dusk sunscreen use important. UVA is responsible for signs of aging, like wrinkles and dark spots. It also damages certain cells in the basal layer of the epidermis, which is where most skin cancers form. In the past, UVA was absolved of a cancer connection. Now, however, researchers believe that it plays a role in cellular changes that lead to cancer.

The other thing to know is that UVA can penetrate clouds and glass. When you're riding in a car, sitting near a window or spending time outdoors in poor weather, you're still in the path of UVA rays. Reflective surfaces, such as water, snow, ice and glass, refract up to 80 percent of the UVA and UVB rays that hit them. That means you're getting close to a double dose of the sun's harmful rays. And don't forget that the sun's rays become more potent at higher altitudes.

Our final word of advice is to be sure to use sunscreen rated for both UVA and UVB radiation. It will be clearly marked on the label. Use it generously and reapply according to product instructions. Your skin will thank you.

(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.)