Relationship between Coffee and Green Tea Consumption and All-cause Mortality in a Cohort of a Rural Japanese Population.

Abstract

We conducted a cohort study to investigate the effects of coffee and green tea consumption on all-cause mortality in a rural Japanese population. Data were obtained from 2,855 men and women aged 40-79 years in 1989, and during the subsequent 9.9 years of follow-up. Using the Cox regression model to adjust for potential confounding factors, we calculated the multivariate hazard ratios of death from all causes separately for men and women. The multivariate hazard ratio of mortality for men who consumed two or more cups of coffee per day, compared with those who consumed less than half a cup per day, was 0.43 (95% confidence interval, 0.30-0.63), and the ratio for those who consumed half to one cup of coffee per day was 0.70 (95% confidence interval, 0.52-0.94). Exclusion of subjects with less than 5 years of follow-up did not substantially change the findings. No other statistically significant associations were identified between consumption of the two beverages and all-cause mortality. For men, multivariate hazard ratios of death from apoplexy showed a significant inverse association with increasing coffee consumption.The effects of habitual coffee consumption and its related factors on health in Japan need to be studied in greater detail.

Non-alcoholic beverage and caffeine consumption and mortality: The Leisure World Cohort Study

“…In another cohort which included older individuals (40-79 years), Japanese men who consumed 2+ cups/day of coffee had a lower mortality risk (RR=0.43) compared with those who consumed less than ½ cup/ day; for those who consumed ½-1 cup/day risk was 0.70 [Iwai 2002]. No statistically significant effect was seen in women.…”

“…However, exclusion of the first five years of follow-up did not appreciably change the mortality and caffeine association. In two studies [Murray 1981,Jacobsen 1986 and in women in a third [Iwai 2002], the increased mortality among those with no or low coffee consumption was limited to the first few years of follow-up. A study of potential confounders contributing to the reported associations of caffeine with disease found that of 32 risk factors only sex and cigarette smoking were important confounders [Schreiber 1988b].…”

“…No statistically significant effect was seen in women. In contrast, other studies have found no association of coffee consumption and mortality [Dawber 1974,Yano 1977 While some prospective cohort studies have found lower mortality among moderate and heavy tea drinkers than among those who drank no tea [Mukamal 2002,Nakachi 2003], others have seen no significant effect [Klatsky 1993,Woodward 1999,Iwai 2002,Stensvold 1992. In a Japanese cohort of 8852 individuals followed for 13 years, increased consumption of green tea was associated with higher ages at death [Nakachi 2003].…”

“…A study of potential confounders contributing to the reported associations of caffeine with disease found that of 32 risk factors only sex and cigarette smoking were important confounders [Schreiber 1988b]. Others have found coffee and tea consumption related to each other and to smoking, alcohol, body mass index, exercise, high blood pressure, diabetes mellitus, heart attack, and soft drink consumption [Murray 1981,Jacobsen 1986,Lindsted 1992,Stensvold 1992,Klatsky 1993,Woodward 1999,Iwai 2002,Kleemola 2002,Mukamal 2002,Mukamal 2004]. In our study, neither adjustment for these and other confounders including age and sex nor stratification by age materially changed the lower risk seen for coffee or caffeine drinkers.…”

“…This increased sensitivity to hyperglycemia may be mediated through the combined effects of reducing substrate delivery to the brain via constriction of the cerebral arteries and increasing brain glucose metabolism and augmenting catecholamine production. In addition, coffee consumption has been inversely related with blood pressure and indices of liver enzymes [Iwai 2002]. …”