Women who took aspirin at least a couple of times a week had a much lower risk of developing lung cancer, whether or not they ever smoked, according to a study of more than a thousand Asian women.     

The findings, published in the journal Lung Cancer, linked regularly taking aspirin to a risk reduction of 50 per cent or more, although researchers cautioned that they did not prove aspirin directly protects against lung cancer.     

But the study does back up a number of previous studies that linked regular aspirin use to lower risks of certain cancers, including colon, prostate and esophageal cancers.     

'Our results suggest that aspirin consumption may reduce lung cancer risk in Asian women,' wrote Wei-Yen Lim, of the National University of Singapore, and colleagues.     

But in an email Lim added: 'The question about whether aspirin use protects against lung cancer is still open to considerable debate at this point, and the published evidence to date is not conclusive.'     

The study included 398 Chinese women diagnosed with lung cancer and 814 cancer-free women, and Lim's team found that women who had used aspirin regularly, at least twice a week for a month or longer, were less likely to have lung cancer.     

Among women who had never smoked, the odds were 50 per cent lower for aspirin users versus non-users. Among smokers, aspirin use was tied to a 62 per cent lower risk of lung cancer.     

The researchers were able to account for some other factors, such as the women's age, education and fruit and vegetable intake, but Lim said there could be still other differences to help explain why aspirin users had a lower lung cancer risk.     

There was a fairly large relative difference in cancer risk between aspirin users and non-users in the study, but the absolute reduction in any one person's risk, if there is one, might be small.     

There are biological reasons that aspirin might offer protection against cancer. It blocks an enzyme called cyclooxygenase-2, or COX-2, which promotes inflammation and cell division, and is found in high levels in tumors.     

But Andrew Chan at Harvard Medical School, who was not involved in the study, said that the evidence on aspirin and lung cancer has been 'mixed.'     

'The number one thing a person can do to minimise the risk of lung cancer is to not smoke,' he said.     

There is stronger evidence that aspirin may be protective against colon cancer, according to Chan, a gastroenterologist who researches colon cancer prevention.     

But he said that it's still too soon to recommend that all middle-aged and older adults take a daily aspirin, although discussing it with their doctor may be reasonable.     

'People are usually interested in more than preventing one particular cancer. So it's important to view this in the context of a person's overall health.'     

The US Preventive Services Task Force recommends that men aged 45 to 79 take aspirin to prevent heart attacks, as long as their personal benefit is likely to outweigh the risk of bleeding. For women age 55 to 79, aspirin is recommended to prevent ischemic strokes, with the same caveat. – Reuters