In this column, we often have written about nutrition and exercise as two pillars of maintaining good health. An equally important lifestyle factor is getting the right quantity and quality of sleep.

During the holiday season, it is easy to get out of sync with your usual sleeping schedule.

QUESTION: How does sleep affect health?

ANSWER: Although excessive sleep has been linked to a variety of health problems, too little sleep is a much more common problem. In the short term, inadequate sleep affects brain function, especially impairing judgment and memory. Millions of college students pulling all-nighters to cram for final exams have experienced this.

Some sleep researchers even have proposed that drowsy driving after too little sleep can be as bad as drunken driving. Just one really late night can throw off a person’s circadian rhythm for as long as a week — similar to jet lag. Under these conditions, the risk for having accidents increases significantly.

Q: Can the effects of ongoing inadequate sleep be cumulative?

A: Years of poor sleep raise the risk for many health problems. People who sleep less than seven hours a night or more than nine hours are more likely to develop both obesity and Type 2 diabetes. Brain diseases also are linked to poor sleep. Dysfunctional sleep commonly accompanies conditions like Alzheimer’s and Parkinson’s diseases.

Some research indicates that years of poor sleep contribute to the risk of developing these brain conditions. Even the risks for high blood pressure and cardiovascular disease increase with ongoing poor sleeping habits.

Q: How much sleep do we need?

A: Sleep researchers suggest that most adults thrive best on seven to eight hours of sleep each night. Some may do better with nine hours, which is still considered to be in the normal range. Some may need a bit more and some can get by on less.

However, those who are genetically set up to effectively function on three to four hours a night are extremely rare, estimated to be as little as 1 percent of the population.

Q: How much sleep should children and teens get?

A: Due to stages of rapid mental and physical development, babies, children and teens need significantly more sleep than adults. Since much of the tissue repair and growth development occurs during sleep, young infants need the most sleep (14 to 17 hours a day).

Sleep needs gradually decline with age, with recommendations for teenagers at eight to 10 hours a day.

Q: What are ways to promote good sleeping habits?

A: The most common recommendations include maintaining a consistent sleep schedule, not napping, using the bed primarily for sleeping (not watching TV, for example), restricting consumption of caffeine and other stimulants too early in the day, avoiding excess alcohol in the evening and keeping a regular exercise schedule (avoiding vigorous exercise within two hours of bedtime).

Of course, we are all somewhat unique in terms of what works best for falling asleep, staying asleep, and waking refreshed. These are the key things to consider if you are having sleeping problems.

THE HOLIDAY season can make it challenging to maintain good sleep hygiene. If you are tempted to push your limits on getting enough good sleep, just remember that the risks inherent in drowsy driving are similar to those of drunken driving. To stay healthy and keep the holidays safe and happy, be sure to do your best to stay on an even keel with your sleep habits.

Alan Titchenal, Ph.D., C.N.S., and Joannie Dobbs, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Dobbs also works with University Health Services.