I agree with this. I've been using a Fitbit for 4 years, and I can see the difference in my sleep on a good night compared to nights I've had alcohol, worked ou

I agree with this. I've been using a Fitbit for 4 years, and I can see the difference in my sleep on a good night compared to nights I've had alcohol, worked out too hard, been dehydrated, had too much caffeine late in the day...they all have measurable differences in my sleep.