It is very common for asthma to get worse at night. This condition is called nocturnal asthma. Although it isn’t proven about why asthma worsens at night, it is believed to be related to certain triggers like your sleeping position, allergens present in the room, excess cooling or perhaps even hormonal fluctuations due to an increase in cortisol levels. Lastly, a sinus infection or a post-nasal drip could also be the reason behind your nocturnal asthma.