Cortisol is a steroid hormone that helps in the bodies response to inflammnation and situations triggering a fight or flight response. Poor sleep can lead to high levels of cortisol. The Cleveland Clinic has a useful article on cortisol and includes the following suggestions for reducing cortisol levels:

• laugh (find humor through the day)
• sleep well
• physical activity
• practice deep breathing
• maintain healthy relationships

Eating close to bed-time can produce elevated cortisol levels in the night, which can lead to waking in the middle of the night and having difficulty getting back to sleep.