Excessive Sleepiness Make an Appointment Find a Doctor Ask a Question Excessive sleepiness is different from fatigue or physical tiredness. Excessive sleepiness may increase the risk of car, work or home accidents. It may also cause poor school or work performance. Memory problems and changes in behavior also can occur. Excessive sleepiness becomes a problem when one cannot stay awake and alert long enough to complete daily tasks. Some types of excessive sleepiness are worse than others. Mild: Sleepiness is mild if it occurs during rest when little attention is required for the activity. Examples including reading or watching television. Moderate: Sleepiness is moderate if it occurs during activities that require more attention. They may be physical or mental. One example is during a group meeting. Severe: Sleepiness is severe if it occurs during physical activities that require full attention. Examples include talking, eating or driving. Programs & Services Sleep Center Clinical Trials For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.