Dear Reader: In our last column, we explored some of the links between sleep deficit and Alzheimer's disease. This was in response to a question from a reader who was worried that his poor sleep patterns, which are becoming more pronounced with age, might put him at risk.

As we said, poor sleep doesn't portend an Alzheimer's diagnosis. But it does have health effects that can range from serious to grave. In the short term, lack of sleep affects learning, mood, memory and coordination. In the long term, chronic sleep deprivation is implicated in diseases like diabetes, obesity, cancer and heart disease.

Experts in the field agree that a healthful night's sleep lasts about eight hours. It is made up of the dream state of REM (rapid eye movement) sleep and several levels of a deeper state known as non-REM sleep. Not only do we need all these phases of sleep for optimal mental and physical health, but we also need them in adequate quantities. There are no shortcuts. And due to the nature of sleep and its effect on the brain and body, it's not actually possible to make up for missed sleep.

The good news is you can take steps to ensure a better night's sleep, but the challenge is following the rules consistently. As we have seen in our own practice, where some sleep-challenged patients can't find the time or impetus to follow through, this can be easier said than done.

Watch the caffeine. From the moment you open your eyes in the morning, a chemical called adenosine is prepping your body for its next sleep cycle. It builds up throughout the day and attaches to receptors in the brain, which then send signals that eventually cause you to feel drowsy. Caffeine blocks those adenosine receptors, so a crucial part of the sleep cycle gets blocked.

While a morning cup of coffee probably won't throw things too far out of whack, caffeine in the afternoon or into the evening can be detrimental to sleep. Alcohol also disrupts sleep. If you're serious about sleeping better, switch to non-caffeinated beverages after breakfast, and skip the nightcap.

Make your life sleep-friendly. Start by putting the screens away at least an hour (some experts say three hours) before bed. Phones, tablets, computers and video games emit so-called "blue" light that disrupts sleep. To our brain and eyes, this light says it's morning. We need the natural light of evening, dusk and then night to signal our internal clocks that it's time to shut down.

Keep your bedroom dark and quiet. Blackout curtains, a sleep mask and earplugs can help overcome disturbances from outside or inside the house. Also, research shows we sleep best in a cool room, from 60 to 68 degrees Fahrenheit.

Set a sleep schedule. Go to bed at the same time each night and get up at the same time each morning. Keep the momentum going on weekends as well.

We know that enacting these changes can be challenging, but keep in mind that good-quality sleep is vital to our physical and emotional well-being. It's worth the effort and the follow-through.

(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: Out of the blue, my new primary care doctor asked me if I owned a gun. Was it appropriate, or even legal, for her to ask that?

Dear Reader: I can understand why you were surprised. Doctors generally try to avoid wading into political discussions, which, as we know, the topic of guns has become. Lately, though, many have been reassessing that arms-length stance and focusing on guns as a public health issue. That's because, as doctors, our concern is preventing illness and injury. We freely speak out against the abuse of alcohol, tobacco and sugar -- all of which are legal -- because we would like to prevent alcohol addiction, smoking and an over-consumption of sugar. Without advocating legal action against these substances, we ask probing questions of our patients and, we hope, give good advice to prevent injury.

The big issue with guns is violence. Put simply, guns are an effective way to injure and kill people -- or, as we think of them, our patients. How many patients? Let me put it this way: In 2015, 36,252 people died of gunshot wounds in the United States. More than 80,000 others are injured each year.

The majority of deaths by firearms -- two-thirds -- are due to suicide. Simply having a gun in the house increases the rate of suicide by gun. This may seem obvious, but having a gun in the house also increases the overall rate of suicide, especially among men. The U.S. rate of suicide by firearm is about 11 times that of other industrialized countries.

Health care professionals particularly worry about depressed patients with access to guns, fearing that those who believe they would be better off dead will more easily act on that belief. Because guns are such an easy, impulsive way to commit suicide, knowing that a gun is in the house can help us more effectively counsel and guide patients.

This is especially useful information when we're counseling military veterans, who have nearly twice the rate of suicide as civilians and who are often comfortable around guns, and when we're assessing overall child and adolescent safety. For adolescents, the rate of suicide is two to three times greater when there is a gun in the house. Further, because of adolescents' poor impulse control, we also worry that they'll use the gun on other people.

Of course, guns in the house are often used for protection. But people with access to a gun have twice the likelihood of being a victim of homicide.

All these statistics lead us to this: Physicians increasingly feel a moral obligation to assess whether a gun is kept in the house and, if so, whether they're kept unloaded and locked in a secure place separate from the ammunition.

It's possible that your physician saw a risk factor -- a history of depression or a potential threat to children -- and is doing her due diligence. It's also possible that she's responding to recent calls from leading physicians to ask all patients about access to weapons within the home.

Regardless, her question was legal -- and meant to protect both you and your loved ones.

(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: I read that not getting enough sleep can increase my risk of Alzheimer's disease. I've had occasional trouble sleeping most of my life, and it seems to be getting worse as I get older. How worried should I be?

Dear Reader: Just like food, water and the air we breathe, getting enough high-quality sleep is vital to our well-being. As anyone who has pulled an all-nighter can attest, lack of sleep can impair reasoning and problem-solving, interfere with learning, and even lead to accidents or injury. Chronic sleep deficit, meanwhile, has been linked to health issues as serious as diabetes, obesity, cancer and heart disease.

Ongoing research continues to find a correlation between sleep deficit and various types of dementia, including Alzheimer's disease. In one of the more recent studies, participants who reported sleep problems like insomnia, poor sleep quality and daytime sleepiness had a measurable increase in amyloid plaques in their spinal fluid. These sticky proteins are considered to be indicators of Alzheimer's disease.

Just how does the sleep-wake cycle affect these Alzheimer's markers? Researchers at the University of Rochester Medical Center believe they have discovered a significant piece of the puzzle. In studies published in 2012 and 2013, they revealed the existence of a cleansing system in the brains of mice, which removes waste products at a rapid pace.

They dubbed it the "glymphatic system" because it mirrors the waste-clearing function of the body's lymphatic system, but is managed by the glial cells in the brain. Unlike cerebrospinal fluid, which plays a crucial role by circulating nutrients to the brain and clearing away debris, the glymphatic system is not passive. It's swift, efficient and reaches all corners of the brain.

What's particularly intriguing is that the glymphatic system is active during deep sleep. Researchers found that during these stages of sleep, the cellular structure of the brain shifts. The spaces between the cells open, allowing the toxins that built up while we were awake to be quickly removed. The glial cells control the flow by shrinking during deep sleep to allow for rapid movement, then swelling again during REM sleep and at waking, all but shutting the system down.

The takeaway is that a good night's sleep, which includes adequate deep sleep, literally clears out the brain. When we skimp or get poor-quality sleep that doesn't include adequate deep sleep stages, we impair the brain's ability to cleanse itself of potentially damaging waste materials.

Thus far, the glymphatic system has been confirmed only in mice. However, the mouse brain is surprisingly similar to the human brain, which is why it is used for study. As scientists build on this research, further discoveries will be made. But at the very least, we are reminded how important sleep is to good health and well-being.

As for your question about whether you should worry, we want to reassure you. Just because a symptom and a disease can be connected, it doesn't mean that they must be. The nature of research like this is to identify patterns for future study. The fact that you have experienced sleep problems does not mean that an Alzheimer's diagnosis is inevitable.

(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.)