that was leading to increased risk.

导致了风险的增高
In fact, it's not the weight itself,

实际上这不是体重本身
it's just that the lower weights are associated with smoking,

而是由于与体重偏低相关联的吸烟
and smoking is what's driving up the mortality.

造成了死亡率的增高
That's why you need--in these studies

所以在这些调查中
you need to look at causation rather than just correlation.

你需要研究因果关系而不仅仅是相关性
The solution to that particular problem was

解决这个问题的办法是
to compare smokers to non-smokers in a sample like this,

对比这个样本中吸烟者和非吸烟者的情况
or you can take statistics and control from the impact of smoking

或者找关于吸烟影响的对照组的统计数据
and find out how much it's contributing

然后找出在它在多大程度上促成了
to that little J part of the curve.

曲线上这个小J形部分的形成
This is interesting,

这很有意思