Humans spend one-third of their lives sleeping, yet 65% of Americans are sleep deprived, says sleep expert James Maas, co-author of the new book "Sleep for Success! Everything You Must Know About Sleep but Are Too Tired to Ask" (AuthorHouse).

But just one extra hour of sleep per night can greatly improve a person's mood, alertness, health and productivity, says Maas, professor of psychology at Cornell.

In the book, co-authored by Cornell graduate student Rebecca S. Robbins while she was an undergraduate, Maas presents the latest scientific research on sleep, much of it conducted in his Cornell sleep lab, where he recently studied the sleeping patterns of 450 Cornell University students.

Maas and Robbins wrote the book with significant help from Sharon Driscoll (while she was a sophomore); Hannah Appelbaum (now in graduate school in social work at Emory University); and Samantha Platt (now in physician assistant school). They are all featured on the book cover and work as part of Maas and Robbins' consulting firm, Sleep for Success, giving presentations on sleeping better to Fortune 500 companies, preparatory schools and such groups as the New York Jets and Orlando Magic.

Their presentations and the new book report such findings as:

• The best predictor of longevity is not exercise or nutrition, but quality and quantity of sleep;

• Most people overestimate the amount they sleep each night by nearly one hour;

• If you fall asleep within five minutes, you are sleep deprived, since the fully rested person takes 20 minutes to fall asleep;

• Women sleep less soundly with a partner than men do; perhaps that's why some 23 percent of American couples sleep apart;

• Every additional hour of sleep reduces a child's risk of obesity by 9 percent;

• One drink of alcohol on six hours of sleep has the same effect on one's ability to drive a car as three to four martinis on eight hours of sleep;

• The best time to exercise is between 5 and 7 p.m. to enhance the depth of nighttime sleep.

Maas' recent studies on high school and college students support the idea that the circadian rhythm of the teenage brain is set to fall asleep at 3 a.m. and wake up at 11 a.m., yet most high school and college students get 2.5 hours less sleep per night than recommended. Grades in high school and college are directly related to sleep length as evidenced by the increase in students' G.P.A. and other measures in studies Maas has conducted.

The book also includes two tests to help the reader determine how well they sleep, the costs of sleep loss and research findings that link poor sleep with colds, flu, unhealthy skin, weight gain, diabetes, heart disease and cancer, as well as stress, anxiety and depression.

In the second half of the book, Maas offers strategies for getting a healthy night's rest -- from the best and worst bedtime snacks and the ideal bedroom environment to tips on purchasing the perfect pillow and mattress and taming a snoring partner (such as tying a tennis ball to the back of his or her nightshirt to keep the snorer on his/her side and less prone to snoring).

The book also includes advice on sleep tips for teens, seniors, shift workers, athletes and women who are pregnant or going through menopause as well as time-management advice to combat stress, tips for managing jetlag and guidelines on sleep medications.

Maas has been teaching Psychology 101 at Cornell University for 47 years, with an enrollment of 1,600 students some years, giving him the record for having taught more than 65,000 students in his Cornell career.