Habitual coffee consumption and blood pressure: A study of self-defense officials in Japan

The study aims to examine the relationship between habitual coffee consumpt ion and blood pressure. The subjects were 3336 male self-defense officials aged 48-56 years, who received a preretirement health examination at the Se lf-Defense Forces Fukuoka Hospital between October 1986 and December 1992. Average coffee intake in the past year was ascertained by a self-administer ed questionnaire. A significant inverse relation between habitual coffee co nsumption and blood pressure was found with and without adjustment for alco hol use, cigarette smoking, body mass index, glucose tolerance, and green t ea intake. Green tea, another major source of caffeine intake in Japanese, was unrelated to blood pressure. The adjusted mean differences per cup of c offee consumed per day were -0.6 mmHg (95% confident interval [CI]: -0.9 to -0.3, p = 0.0001) in systolic blood pressure and -0.4 mmHg (95% CI: -0.5 t o -0.2, p = 0.0002) in diastolic blood pressure. Habitual coffee drinkers h ad lower blood pressure than non-drinkers at any levels of alcohol use, cig arette smoking, obesity, and glucose intolerance. Our findings consolidate the previous observation that habitual coffee consumption was associated wi th lower blood pressure.