Not OP, but you have to keep in mind that your body is always trying to repair any damages that happen. Be it through actual accidents or molecular mishaps. Stress and other factors can cause the body to go into survival mode, where all resources are allocated to solving only the challenge directly ahead at the expense of repairs. And your body always needs repairs, because there is so much stuff going on at the molecular level that wears down the cells. Our bodies are pretty good at repairs but not perfect.
I worked myself into the dirt for 2 years for a start-up that ended up failing. It felt like I aged 10 years. My hairline receded an inch - my hair started going grey - and I gained 15kg.
I'm undoing the damage now - but I can tell I've been physically aged by the process.
Our physiology is not built to work under sustained high stress and a constrained environment like fast moving startups can have long term health effects.
Maybe, but not necessarily. It's all probabilities. A fatal heart attack in 2 years being X% more likely is one thing - actually having it happen and dying young from it is another thing entirely.
I'm not so sure. Like of financial worries is also dangerous - it can make people uber-complacent and lazy coach surfers, which will weaken the person long-term. Similar to how lack of gravity in space leads to significant loss of muscle mass.