People recently diagnosed with lung cancer are at higher risk of having a stroke than those without lung tumors, 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 who 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.
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.
Background and Purpose - Stroke is a known cerebrovascular complication in lung cancer patients; however, whether lung cancer patients are at elevated risk of developing stroke relative to the noncancer population remains unclear.
Methods - The present study used population-based claims data from the Taiwan National Health Insurance, which identified 52 089 patients with an initial diagnosis of lung cancer between 1999 and 2007, and 104 178 matched noncancer subjects from all insured subjects age 20 years and older. Subsequent occurrence of stroke was measured until 2008, and the association between lung cancer and the hazard of developing stroke was estimated using Cox proportional hazard models.
Results -The incidence of stroke was 1.5 times higher (25.9 versus 17.4 per 1000 person–years) in the lung cancer group compared with the comparison group. The multivariate-adjusted hazard ratio (HR) comparing lung cancer patients with the noncancer group was 1.47 (95% CI, 1.39–1.56) for stroke, 1.78 (95% CI, 1.54–2.05) for Hemorrhagic stroke, and 1.43 (95% CI, 1.34–1.51) for ischemic stroke. The risk of stroke fell over time, decreasing after 1 year of follow-up for men and after 2 years of follow-up for women. Within the first year of follow-up, the risk of stroke peaked during the first 3 months for men and within 4 to 6 months for women.
Conclusions - Lung cancer is associated with increased risk of subsequent stroke within 1 year after diagnosis for men and 2 years after diagnosis for 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.
Lung cancer linked to risk of stroke" class="border" /> Some evidence suggests that excessive bleeding and blood clots, both of which can be caused by tumors, 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.
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.
According to the American Lung Association, smoking is directly responsible for approximately 90 percent of lung cancer deaths.
“In the U.S., 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 U.S. in 2007, based on a report by the American Heart Association.
SOURCE: Stroke, September 13, 2011.
1. Pei-Chun Chen, PhD;
2. Chih-Hsin Muo, MS;
3. Yuan-Teh Lee, MD, PhD;
4. Yang-Hao Yu, MD;
5. Fung-Chang Sung, PhD