CoVee and tea consumption in the Scottish Heart Health Study follow up: conflicting relations with coronary risk factors, coronary disease, and all cause mortality

Study objective—To relate habitual (cups per day) tea and coVee consumption to conventional coronary risk factors and subsequent risk of coronary heart disease and death. Design—Cohort study. Setting—Nationwide random population study. Participants—Over 11 000 men and women aged 40–59 who took part in the Scottish Heart Health Study lifestyle and risk factor survey in 1984–87. Participants were followed up to the end of 1993, an average of 7.7 years, for all cause mortality, coronary death, or any major coronary event (death, non-fatal infarction or coronary artery surgery). Cox’s proportional hazards regression model was used to estimate the hazard in consumers of tea and coVee relative to the zero consumption group, both before and after correction for other factors. Main results—CoVee and tea consumption showed a strong inverse relation. For many conventional risk factors, coVee showed a weak, but beneficial, gradient with increasing consumption, whereas increasing tea consumption showed the reverse. Increasing coVee consumption was associated with beneficial eVects for mortality and coronary morbidity, whereas tea showed the opposite. Adjusting for age and social class had some effect in reducing associations. Multiple adjustment for other risk factors removed the associations for tea and most of those for coVee although there was a residual benefit of coVee consumption in avoiding heart disease among men. Conclusions—The epidemiological diVerences shown in this study occurred despite the pharmacological similarities between tea and coVee. Either they diVer more than is realised, or they identify contrasting associated lifestyle and health risks, for which this multiple adjustment was inadequate. (J Epidemiol Community Health 1999;53:481–487) CoVee drinking has been said to provoke arrhythmias and dilate coronary arteries, although the available evidence is sometimes contradictory. Meta analyses have either found no overall eVect of coVee on coronary heart disease (CHD) 3 or an eVect only in case-control studies. 5 Tea drinking has been thought to be of potential benefit for avoiding CHD, mainly because of antioxidant constituents. 7 The general picture from past research is similar for other diseases, including cancer: large amounts of coVee might constitute a risk 9 but tea drinking might be protective. 10 Despite the general impression that high coffee consumption is “bad”, we have previously found the prevalence of CHD to be highest among those who abstain from coVee drinking and lowest among those who drink five or more cups per day in Scotland. The purpose of the current article is to see whether the previous findings are reproduced when incidence data are used. The study group has been monitored longitudinally for all cause mortality, as well as CHD, and both are reported here. Unlike many previous cohort studies, this study uses a large random population sample of both men and women. Studies on specific groups 13 may lack general applicability. Relatively few studies have been carried out in the United Kingdom, especially with regard to tea. Methods The Scottish Heart Health Study (SHHS) randomly sampled men and women aged 40–59 years from 25 districts in Scotland between 1984 and 1987. The response rate was 74%. Each participant completed a postal questionnaire and attended a clinic where it was checked, a 12 lead electrocardiogram (ECG) was applied and a blood sample was taken. CoVee and tea consumption were reported as the number of cups usually drunk Table 1 Spearman correlations for coVee and tea consumption by sex