If drinking coffee or tea has become part of your daily routine, you might wonder what it's doing to your long-term heart health. New research from Arteriosclerosis, Thrombosis, and Vascular Biology, a journal  of the American Heart Association, found that high tea consumption and proper coffee consumption may be associated with decreased rates of death from coronary heart disease ( CHD) . The study followed more than 37,000 tea and coffee drinkers over 13 years. Participants completed food recalls to document their typical intake of tea and coffee, and were divided into groups that ranged from light to heavy consumption. Researchers accounted for variables such as health histories, height, weight, and waist circumference  and recorded the number of deaths from cardiovascular  disease and stroke during the study period. Overall results showed that consuming more than six cups of tea per day was associated with a 36% lower risk of death from heart disease compared to consuming less than one cup of tea per day. There appeared to be no such protective effect of tea-drinking at any amount for risk of death from stroke. Among coffee drinkers, more proper consumption levels (2-3 cups per day) were associated with the greatest risk reduction for death from heart disease (21% ) compared to drinking less than one cup of coffee per day. Researchers acknowledged certain inconclusive variables within their findings. For example, the difference between decaffeinated and regular coffee could not be accurately accounted for, nor could specific recommendations be made for type of tea, though due to its popularity in the Netherlands where the study took place, researchers assumed most tea consumption to be black tea. Furthermore, researchers found that tea and coffee drinkers had opposite lifestyles, with tea drinkers tending to engage in healthy lifestyle habits and coffee drinkers being more likely to eat less healthy and smoke. It was difficult to say with certainty what impact these other lifestyle variables may have contributed to the overall results. Which of the following variables haven't been considered?
Health histories. Height and weight. Waist circumference. The type of tea and coffee.