People who live in Houston, Dallas, or Austin may be particularly vulnerable to the effects of sleep deprivation, since the stresses of city life can put undue pressure on the human body.

While modern culture may not look favorably on the idea of a mid-day nap, research shows that people can make themselves more alert while reducing stress and improving cognitive functioning through the use of a "power nap." When they do so, they end up having more patience, less stress, better reaction time, increased learning, more efficiency and better health.

How much sleep is enough? Experts say the human body needs seven to eight hours of sleep per day. Getting fewer than six hours is said to triple the risk of a car accident. There is also a cumulative effective, with the loss of sleep on one day creating a sleep deficit which can impair reaction time, judgment, vision, information processing, short-term memory and performance.

Motivation, vigilance and patience can also be negatively affected by too little sleep. Those who are fatigued can also experience more moodiness, aggressive behaviors, burnout and more stress.

Studies show that 20 minutes of sleep in the afternoon provides more rest than 20 minutes more sleep in the morning (though the last two hours of morning sleep have special benefits of their own). Experts say the body seems to be designed for this, as most people's bodies naturally become more tired in the afternoon, about eight hours after waking.

So how long should someone sleep? Answering that question means better understanding the nature of sleep. We pass through different stages of sleep, known together as a sleep cycle, including light sleep, deep sleep (believed to be the stage in which the body repairs itself), and rapid-eye movement sleep, or REM sleep (during which the mind is repaired).

Many experts advise to keep the nap between 15 and 30 minutes, as sleeping longer gets you into deeper stages of sleep, from which it's more difficult to awaken. Longer naps can also make it more difficult to fall asleep at night, especially if sleep deficit is relatively small.

Even so, other research supports the contention that a one-hour nap can help produce a much greater improvement in cognitive functioning. The key is to get a sense of how long someone's sleep cycles are since the interruption of the sleep cycle is what makes someone groggy.

Sleep experts say a good strategy is to let the person's schedule decide: there may only be 15 minutes to spare, but if someone can work in an hour nap, they may do well to complete an entire sleep cycle, even if it means less sleep at night.

With only five minutes to spare, a person could close their eyes, since even a brief rest has the benefit of reducing stress and helping someone relax a little, giving them more energy to complete the tasks of the day.

People who want to obtain more sleep, and enjoy the health benefits that go with getting enough sleep, should consider avoiding caffeine after 3 p.m., since caffeine is a stimulant that can disrupt sleep and stay in the system longer than someone might think (half life being four to six hours).

If you don't want to nap a long time, set an alarm. If you don't have time for a power nap, or don't feel comfortable napping during the day, try meditation; it gives your body a rest and produces slower brain waves similar to sleep.

Benefits of sleep include:

-Keeping your heart healthy. Heart attacks and strokes are more common during the early morning hours with lack of sleep associated with worsening of blood pressure and cholesterol, all risk factors for heart disease and stroke. Experts say a person's heart will be healthier if they get between seven and nine hours of sleep each night.

-Preventing cancer. People working the late shift have a higher risk for breast and colon cancer. Researchers believe this link is caused by differing levels of melatonin in people who are exposed to light at night. Light exposure reduces the level of melatonin, a hormone that both makes us sleepy and is thought to protect against cancer, suppressing the growth of tumors.

-Reducing stress. When your body is sleep deficient, it goes into a state of stress. The body's functions are put on high alert, which causes an increase in blood pressure and a production of stress hormones. Higher blood pressure increases the risk for heart attacks and strokes.

-Reducing inflammation in the body. The increase in stress hormones raises the level of inflammation in your body, also creating more risk for heart-related conditions, as well as cancer and diabetes. Inflammation is thought to be one of the causes of the deterioration of your body as you age.

-Sleeping well can also keep someone more alert. Being engaged and active not only feels great, it also increases a person's chances for another good night's sleep. When someone wakes up feeling refreshed, they should use that energy to get out into the daylight, do active things, and be engaged. They'll sleep better the next night and increase their daily energy level.

Getting the proper amount of sleep is an important way to stay healthy, regardless of age. How you take care of yourself will certainly affect you as you age, and eventually your wallet, as well.