…according to an article at Annals of Internal Medicine. The study was done in a U.K. population over decade of observation. The 10% or greater reduction in all-cause mortality was seen at a habitual consumption level of two or more cups of black tea daily. Most prior similar studies I’ve seen focus on green tea.
Steve Parker, M.D.
Diabetic Mediterranean Diet 
Your title uses causal language, but the study you reference does not look at causality at all.