Alone in the Semi-Dark

I had a lot of trouble getting sleep on my last trip to the U.S. I hatched several theories as to why this was the case:

1) Jet Lag - perhaps my body clock was really still on Philippine time, and when my conscious mind was thinking "time to hit the sack and get some shuteye", my body was thinking "hm? an afternoon nap? Okay!";
2) Altitude - perhaps my body was used to being closer to sea level, and I was getting antsy because being up in the hills of Belmont forced me to extract more oxygen from the thin atmosphere;
3) Aridity - since the Bay Area is a lot less humid (read: dry) than the Philippines, it seems to have sucked the moisture from my throat causing some discomfort during breathing and a more rapid need to replenish moisture;
4) Temperature - the warm feet / cold head technique was often used to keep this sleepy driver from dozing off at the wheel, but it may have kept me awake in bed given my lack of hair this time around.

Of course, it's also likely that I'm just not used to sleeping alone anymore and I was subconsciously seeking out the presence of my lovely wife.