> Spending time horizontal while not asleep is very unhealthy for your heart.
Why is this?
Why is this?
[0] https://www.betterhealth.vic.gov.au/health/healthyliving/the...
see my other comment for other references: https://news.ycombinator.com/item?id=40549893
Your references are due to sedentary, not laying down. You can have a sedentary life standing in place most of the day. Likewise, the problem is being sedentary, not what position your sedentary in.
The less time that your heart has to fight against pressure/gravity, the weaker that muscle will become. This is pure causation.