Smoking negates moderate alcohol benefits on stroke risk

Caroline Cassels

April 14, 2010

Toronto, ON - Any potential beneficial effect of moderate alcohol consumption on stroke risk appears to be negated if individuals also smoke, new research suggests[1].

Presented here at the American Academy of Neurology 2010 Annual Meeting , a large prospective study of 10 171 men and 12 353 women who were followed for incident stroke showed the association between alcohol consumption and stroke was significantly different between smokers and nonsmokers.

Nonsmokers who consumed moderate amounts of alcohol, defined as two to three units (a unit of alcohol was approximately 8 g, a regular glass of wine) per day, were 37% less likely to develop stroke than nondrinkers.

Yangmei Li

According to the study investigator Yangmei Li (University of Cambridge, UK), the potential link between alcohol consumption and stroke risk is unclear. While research shows heavy alcohol use increases stroke risk, the relationship between light to moderate drinking and stroke is less obvious, with considerable variation between studies.

To examine the prospective association between alcohol consumption and stroke, investigators gathered data on individuals in the general population who were participating in the European Prospective Investigation into Cancer-Norfolk (EPIC-Norfolk) study.

Participants were aged 39 to 79 years without known heart attack, stroke, or cancer at the baseline period in 1993 to 1997 and were followed for incident stroke.

At 12-year follow-up, 864 incident strokes were observed. Compared with nondrinkers, the hazard ratios and 95% CIs for stroke for participants who consumed alcohol were U-shaped, so that mild to moderate drinking decreased stroke risk, while heavy alcohol consumption increased risk by amount consumed.

Associated stroke risk by weekly alcohol consumption

Units/wk, n HR (95% CI)
0.1 - 3 0.72 (0.60-0.86)
3.1 - 7 0.56 (0.45-0.70)
7.1 - 14 0.55 (0.44-0.70)
14.1 - 21 0.71 (0.53-0.95)
21.1 - 28 0.82 (0.55-1.21)
>28 0.96 (0.67-1.39)

However, according to the study findings, this protective effect appears to be negated by smoking.

Age-adjusted hazard ratios, compared with never-drinking, never smokers

Category HR (95% CI)
Current-drinking, never smokers 0.75 (0.52-1.09)
Never-drinking, former smokers 0.62 (0.22-1.75)
Current-drinking, former smokers 0.88 (0.61-1.26)
Never-drinking , current smokers 0.73 (0.18-3.06)
Current-drinking, current smokers 1.75 (1.17-2.62)

"Mild to moderate alcohol use may reduce risk of stroke, but according to our results, heavy drinkers will not experience a reduced risk and in fact may increase their risk of stroke. We know that smoking has a negative effect on stroke risk, [and] smoking in combination with moderate drinking seems to counteract [the] potential benefit [of alcohol]," Li commented.

Dr Ralph L Sacco

Commenting on the study, Dr Ralph L Sacco (University of Miami Jackson Memorial Hospital, FL) said that, like a number of previous papers, including research by his team in the Northern Manhattan Study (NOMAS), these new findings confirm that "moderate alcohol use is absolutely protective against stroke."

"We have demonstrated in NOMAS on two different occasions that moderate alcohol use is protective; however, we did not find any interactions with smoking. In fact, [in NOMAS] we found [the protective effect] was independent of smoking," said Sacco.

"It was interesting to see that in this large European cohort moderate alcohol use was not protective among smokers. The bottom line, which is no surprise to anyone, is that you absolutely shouldn't smoke, and this study seems to suggest that smoking is such a potent risk factor and has such a direct toxic effect on the blood vessels' endothelium that it overwhelms the small protective effects of alcohol," he added.

Li reports no relevant conflicts of interest. The study was supported by the Medical Research Council UK/Cancer Research UK .

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