答：这与so am I.So do I,So is he.表示前者情况适用于后者不是一回事.
与so I am,so it is ,so he does,表示赞同对方的观点也不是一回事.
这一句没有这个so,是一个一般疑问句：Is sth.bad for us?
sth.= all of this time sitting behind the wheel
查辞典,它属于conj.用法：
2 used as a way of making certain that you or someone else understand something correctly,often when you are repeating the important points of a plan:
So we leave on the Thursday and get back the next Tuesday,is that right?
译：这么说来,开车的这段时间对我们来说都是有害的了?