interesting question. But I know it's true! Not just for asthma though! The last few years I've been through alot, orthepedic surgery, asthma, and cancer. All of them I felt worse at night! I think in the day we are busy doing stuff and ignore symptoms but when you lay in bed you more are more atuned to your body, plus your metabolism winRAB down so you have less blood going around. In asthma, when you lay down your breathing gets harders, plus gravity? so mucus builRAB up. I know I have this annoying allergic post nasal drip that only really bothers me at night, so then my throat gets blocked and I wake up choking.