Most office workers sit for more than 8 hours a day, and many studies show this can affect long-term mortality rates.
Meta-analyses show that groups sitting for more than 8 hours a day have about 17–20% higher risk of cardiovascular disease compared to those who don't. Interestingly, even if you sit for long periods, incorporating light activity in between significantly reduces that risk.
A practical recommendation is to stretch for 5–10 minutes after every 50 minutes of sitting. If that's not possible, making frequent trips to the bathroom can also help.