Dear Doctor: My husband has fallen into a strange sleep pattern. Some nights he’s awake until 3 a.m., tosses and turns all night, then wakes up tired. I’ve read that strange sleep cycles may be linked to Alzheimer’s disease, which his mother had. I’m worried, but what can I do?

Dear Reader: First, a bit of reassurance. More than half of older adults report having problems with sleep, including difficulty falling asleep, too much time spent in light sleep, waking up too often during the night and having trouble staying asleep. These can be the result of illness, anxiety, depression, life changes, a side effect of certain medications, too much electronic screen time or poor sleep habits.

It’s true that disrupted sleep is common among people who have been diagnosed with Alzheimer’s disease. They sleep less during the night, and the quality of that sleep is often poor. As a result, they spend their days feeling drowsy and will often take naps or sleep for hours at a time. Recent research suggests that the onset of fitful or fragmented sleep can also be an early indicator of Alzheimer’s disease, one that precedes the more well-known symptoms of memory problems and cognitive changes.

A study published last year in the journal JAMA Neurology found that people with no obvious cognitive issues, but whose sleep cycles had become altered, were more likely to have clumps of certain types of proteins in their brains. Known as amyloid plaques, these clumps collect between neurons and disrupt the cellular function in the brain.

Another study, published earlier this year in the journal Science Translational Medicine, also assessed sleep patterns in people with no memory or behavioral problems. The researchers found that a drop in the quantity of slow-wave sleep that someone got each night -- that’s the deep sleep that leaves you feeling rested and refreshed -- was associated with a buildup of a brain protein known as tau. Elevated levels of tau brain proteins, which form tangles in the brain and lead to atrophy, are commonly seen in people with Alzheimer’s disease.

Since your husband’s family has a history of Alzheimer’s disease, we suggest that you consider broaching the subject with your family doctor. There is no single test for Alzheimer’s disease at this time, but your doctor has access to a variety of diagnostic tools that can be helpful. This includes taking a detailed medical history, and using specially crafted verbal tests designed to assess cognitive function. If it appears to be necessary, your doctor may suggest a neurological exam that includes brain imaging. Taken together, these will establish a baseline for future comparison.

Cognitive issues aside, getting an adequate amount of high-quality sleep each night is important to many areas of health and well-being. We encourage your husband to discuss his changing sleep patterns with his doctor. It’s possible that they can uncover and address an underlying cause of the change.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Several studies have shown a correlation between marijuana use and low birth weight, and I understand that marijuana today has been cultivated to be much stronger than what was used in earlier years. Should this be a concern for women who are pregnant?

Dear Reader: We’ve written before about the use of marijuana, also referred to as cannabis, during pregnancy, specifically in relation to morning sickness. And while it’s true that cannabis is effective in easing nausea, we recommend against its use during pregnancy.

Cannabis is a complex plant that contains hundreds of chemical compounds, including those with psychoactive effects. Science’s understanding of cannabis’s properties, as well as its long-term effects on the human body, is in its early stages. What we do know is that chemicals in cannabis can pass through a woman’s body and into her fetus, and that may affect development.

Several recent studies have drawn a connection between cannabis use during pregnancy and low birth weight, a term that refers to infants born weighing less than 5 pounds, 8 ounces. Although low birth weight infants can be healthy, they are also at increased risk of complications such as an inability to fight infection, having trouble eating and not gaining weight.

Cannabis use in pregnancy also has been linked to increased risk of preterm birth. A recent study from the Colorado School of Public Health analyzed health data from 3,200 women and found that cannabis use during pregnancy was associated with a 50% higher risk of low birth weight. Close to 90% of women in the survey who had used cannabis during pregnancy also breastfed their babies, adding another unknown to the equation.

As you mention, cannabis products today are 6 to 7 times more potent that they were in the 1970s, according to some estimates. Meanwhile, cannabis use among women who are pregnant has increased more than 60% between 2002 and 2014, according to the National Survey on Drug Use and Health. Current research suggests that 4% to 7% of pregnant women now use cannabis, often in the early months of pregnancy to deal with morning sickness. In a study published earlier this year, which also found a link between cannabis use and low birth weight, 22% of the 2,173 pregnant women screened positive for cannabis use.

Our advice against cannabis use during pregnancy is not based on any specific study. Rather, it’s because too little is known about how the chemical compounds in cannabis may affect a developing fetus or a child’s later development. In our opinion, that lack of knowledge makes the potential risks of cannabis use during pregnancy too great at this time.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I’m in my 70s, and I work about 35 hours a week doing shipping, cleaning and light lifting. I’ve stopped visiting the gym because I’m too tired after work. My back hurts, and I’ve had heart issues recently, leaving me with a pacemaker and defibrillator. Are the 10,000 steps I walk at work each day enough exercise?

Dear Reader: The 10,000 steps you are logging each day are to be celebrated at any age. Add in a physically active job and your wish to stay connected to your work community, and we think you are making many good choices. The interactions of a workplace offer purpose and camaraderie. And the health benefits of human connection -- particularly among the elderly -- are well-documented. These include a reduced risk of cardiovascular problems, inflammatory issues and cognitive decline.

In discussing the scope and rigor of exercise with our older patients, we encourage them to listen to their bodies. They themselves are the best teachers when it comes to what types of exercise to take part in, and how much to do. Our approach is to break physical exercise into four basic categories -- endurance, resistance, flexibility and balance. In terms of plain old numbers, the American Academy of Family Physicians recommends at least 2.5 hours of moderate aerobic exercise spread out over the course of a week. This is exercise that raises the resting heart rate, such as brisk walking.

Your work, which in addition to those 10,000 daily steps has some strenuous elements, is contributing to that recommendation. However, to balance things out, you might consider adding resistance exercises, like lifting free weights. Resistance exercise helps prevent osteoporosis and frailty, builds and maintains muscle mass, improves balance and improves mood and cognition.

Flexibility exercises such as yoga or tai chi are also an important element of regular exercise, and they also help with balance. Senior and community centers often offer these and other flexibility classes targeted to older bodies. Just be sure to let the instructors know about any physical problems you have, including the back issues you mentioned in your letter.

You wrote of having heart problems in the recent past. Since you have both a pacemaker and a defibrillator, we strongly recommend that you see your primary care physician to discuss your current and any future exercise regimens. While moderate exercise with either of those devices is generally considered safe, certain adjustments may need to be made to accommodate the implanted devices.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)