Many American high school students are not getting the recommended amount of sleep at night, a Columbia University study suggests.

Researchers found that only 6.2 percent to 7.7 percent of females and 8.0 percent to 9.4 percent of males reported getting nine or more hours of sleep. The Centers for Disease Control and Prevention recommends that adolescents get nine or 10 hours of sleep each day. Among 12th graders, approximately 95 percent of males and females did not meet this recommendation, the study found.

Researchers found a consistent pattern in females' sleep habits. The number reporting nine or more hours of sleep per night decreased as grade level increased. The same general pattern was found for males. Without exception, compared with 9th graders, a significantly lower percentage of 11th and 12th graders reported obtaining nine or more hours of sleep and, except in 2009 and 2013, a significantly higher percentage of 11th and 12th graders reported getting five or fewer hours of sleep.

Research: Prevalence of Sleep Duration on an Average School Night Among 4 Nationally Representative Successive Samples of American High School Students, 2007-2013, Charles E. Basch, PhD, Preventing Chronic Disease, published 11 December 2014.