One or two drinks a day can raise the risk of developing hypertension in some men, according to two Japanese studies.
The studies, published in the July issue of Alcohol: Clinical Experience and Research, found that men who had as few as one or two glasses of alcohol on a regular basis had a much higher incidence of hypertension than those who did not drink at all.
Several US studies have found that moderate drinking habits can actually decrease the risk of heart disease. American studies have also found that regular alcohol consumption does not affect hypertension risk below a threshold of three to six drinks.
Two general differences between Japanese and American populations may help explain the difference in findings of these studies.
First, there is significantly more obesity in the United States than in the Japanese population. A higher blood-alcohol level can be expected in a lower-weight population at similar drinking levels, potentially resulting in a lower threshold effect.
Second, about 50 per cent of Japanese people have a genetic defect that affects the metabolism of alcohol. However, recent studies of this defect have found no effect on risk of hypertension.
In the first Japanese study, Susumu Ohmori, M.D., and colleagues at Kyushu University found that up to a point, the incidence of hypertension rose with the amount of alcohol men drank.
Ex-drinkers, who had not had a drink within three months, were still nearly twice as likely to develop hypertension as men who did not drink at all. Those who drank a moderate amount on a regular basis had an even higher incidence and those who had more than a couple of drinks a day had about a threefold higher incidence of high blood pressure than non-drinkers.
The study involved more than 1000 residents of Hisayama Town, a suburban community. The researchers studied the subjects over a 10-year span. The study included men and women, but the heightened risk of hypertension was found only in the men.
Ohmori and colleagues said: "Regular drinking, including even low levels of consumption, was found to be a significant risk factor for the onset of hypertension in a general population of Japanese men."
The second study included only male office workers, but produced strikingly similar results.
Men who averaged even just one drink a day had a 20 per cent to 30 per cent increased incidence of hypertension, depending on their age at the beginning of the study. The more they drank, the higher their risk, falling just shy of a threefold increase among the heaviest drinkers, found Dr Noriyuki Nakanishi, of Osaka University Graduate School of Medicine, and associates.
The study involved nearly 3,800 men who did not have hypertension at the beginning of the study. Nearly 1,000 developed hypertension during four years of follow-up.
Both studies note that they lacked any dietary or nutritional information on their subjects, another possible source of hypertension risk.
However, Nakanishi and colleagues concluded that their findings "suggest that the risk for hypertension increases in a dose-dependent manner as alcohol intake increases in both young and middle-aged Japanese men and that light to moderate alcohol consumption has an important influence on [blood pressure] in Japanese men."
The study was funded by the Arteriosclerosis Prevention Association in Tokyo.