根据以下内容回答题：An occasional drink with dinner could reduce the risk of having a stroke（中风），according to a new study．Researchers found that light to moderate drinkers can lower their risk by about 20 per cent compared with nondrinkers． The study was the biggest ever to examine the link between alcohol and stroke．It showed that as little as a single glass of wine or beer per week can significantly reduce stroke risk．The study involved more than 22，000 men，but the researchers said the results could also apply to women． However，the researchers stressed it would be unwise for doctors to advise patients who don’t drink to suddenly start or those who drink small amounts to begin consuming more heavily．The study found no added protection from stroke by drinking more than lightly or moderately． And researchers warned of possible harms posed by alcohol，such as liver damage，the dangers of driving while drunk and the risk of breast cancer in women． What’S more，there are other ways to reduce stroke risk，such as quitting smoking or lowering blood pressure． Numerous studies have shown that modest drinking reduces the risk of heart disease．But until now，the evidence of an effect on strokes has been less convincing．Early studies were criticized because they simply compared drinkers to non-drinkers．This latest study examined varying levels of alcohol intake．It found that between one drink a week and one a day reduces the risk，and the lesser amount was about as good as the higher one． The study was the biggest ever because__________ ．