This is a high quality study that does take into accounts covariates like age, sex, pre-existing health condition, socioeconomic factors etc, etc.
One surprising finding is that cycling to work prevents cancer (51% reduction) more strongly than cardiovascular diseases (37% reduction). You would think it's the other way around.


The only downside is that we are hospitalized for traffic accidents at 1.98X the rate of non-cyclists. So be careful out there!