Sakurai recently sat down with Nintendo Dream for a massive interview which covered a wide range of topics. In that interview, we get to hear about Sakurai's overall health.

Fans who follow Sakurai's work on the Smash Bros. series know that he sometimes has some rather stressful health issues, and unfortunately, it seems he had his fair share during Smash Bros. Ultimate's development. The comments below come directly from Sakurai, and were spliced together to paint the full picture of his health troubles.
I made some changes from what I used to do compared to now. For example, as a principle, I always left the office by 10 PM, no matter what. Many companies are discouraging extreme overtime these days, too. ...Well, actually... I still had a lot of stomach problems.
...I've had that situation once or twice before during development. It was like I got food poisoning from some oysters that I didn't eat. It was like my food had come into contact with them or something. But I cook my food thoroughly... Why did I get sick"

...I just get an IV drip and go to work like normal. I guess I'm a hard worker" (wry laughter) I'm a freelancer, so I don't have any strict rules on my time. As long as I can complete the game, I could show up to the office once per week and I think it'd be within the realm of forgiveness. But instead I make sure I come to work every day and write proper daily reports and such. I'm always working, bu...