Night... Nocturnal refers to night time. So, nocturnal asthma is present when an asthmatic awakens from sleep with asthma sxs like shortness of breath, cough, etc. There are medications that can be given to try to prevent this from happening. Keep track of how often this happens, what time the awakenings occur, exact sxs present, etc so your doctor can prescribe an effective regimen for you.
Nighttime symptoms. If you think you have persistent asthma but don't have symptoms at night you probably don't have asthma. Except in its mildest forms asthma is almost always worse at night. Your body's own supply of corticosteroids & bronchodilators, both produced in the adrenal glands, reaches its daily low point at night resulting in increased inflammation in the breathing tubes. It's 2 am & you're coughing.