People recently diagnosed with lung cancer are at higher risk of having a stroke than those without lung tumours, suggests a large new study from Taiwan.
Researchers looking at data covering more than 150,000 adults found that among those with lung cancer, 26 in every 1000 experienced a stroke each year, compared with 17 in 1000 that did not have cancer.
"This is one more telling sign of the long term risk of smoking," said Dr Andrew Russman, a stroke specialist at the Henry Ford Hospital in Detroit, who was not part of the study.
The Taiwanese researchers didn't factor in lifestyle issues – such as smoking, drinking or diet – that might influence stroke risk, explained senior author, Dr Fung-Chang Sung of the China Medical University, to Reuters Health in an email.
Decreased risk after time
Still, they report in the journal Stroke, that stroke risk was highest during the first three months after lung cancer diagnosis for men and during the first four-to-six months for women. Risk decreased in men after one year and after two years in women.
They also found that a less common type of stroke – hemorrhagic stroke, caused by sudden bleeding into the brain – occurred more often among the lung cancer patients than ischemic stroke, which is usually caused by a clot blocking blood flow to brain tissue.
Some evidence suggests that excessive bleeding and blood clots, both of which can be caused by tumours, as well as chemotherapy side effects, could partly explain the apparent link between cancer and stroke, researchers note.
"The most common type of lung cancer, adenocarcinoma, increases the body's propensity to form blood clots, even more so than other types of cancers," Russman told Reuters Health.
Blue collar workers
More than 52,000 people with lung cancer and more than 104,000 people without lung cancer were selected from a nationwide health insurance database.
Most of the study population were blue-collar workers such as farmers, fishermen and vendors, who tended to have high blood pressure, diabetes and heart disease.
"There's a higher rate of high blood pressure and diabetes and pulmonary disease in patients with lung cancer," said Russman. "I think this reflects the heavy burden of smoking and smoking related risk factors in the population," he said.
Smoking direct cause of death
According to the American Lung Association, smoking is directly responsible for approximately 90% of lung cancer deaths.
"In the US smokers have twice the risk of having a stroke, regardless of lung cancer," said Russman.
Stroke accounted for one out of eighteen deaths in the US in 2007, based on a report by the American Heart Association.
(Reuters Health, September 2011)