Smoking causes far more cancer deaths in Asian-Americans than previously thought

Korean, Chinese, Japanese, and Vietnamese American males living in California die of cancer at three times the rate of South Asian females in California, whose cancer mortality rate is one of the lowest in the world.

According to a new study by UC Davis Cancer Center researchers, such disparities between genders and Asian and Pacific Islander ethnic groups can be explained almost entirely by tobacco smoke exposure - suggesting that if smoking were eliminated, Asian and Pacific Islander Americans all would have very low cancer mortality rates, with minimal variation from group to group.

"Among Asian Americans and Pacific Islanders, non-lung cancer death rates, like lung cancer death rates, correlate very closely with their smoke exposures," said Bruce N. Leistikow, associate professor of public health sciences at UC Davis and a leading expert on the epidemiology of smoking-related illnesses. "If all Asian and Pacific Islander Americans had as little smoke exposure as South Asian females in California, our work suggests that their cancer mortality rates across the board could be as low as that of the South Asian females."

South Asian females in California had a cancer mortality rate of 58 deaths per 100,000 people per year. The cancer mortality for the United States as a whole was 193.5.

The UC Davis study appears online ahead of print in Preventive Medicine. It provides the first published evidence of associations between smoke exposure and non-lung cancer mortality in Asian and Pacific Islander Americans. These associations held up across California, Hawaii, Illinois, New Jersey and New York, states that are home to 63 percent of the total Asian and Pacific Islander population in the United States. The associations also held up across Chinese, South Asian, Japanese, Korean, Filipino, and Vietnamese Californians. The study examined mortality data covering several periods between 1980 and 2002.

"The associations remained consistent across gender, Asian-Pacific Islander ethnic group, state of residence, and year - despite substantial differences among the populations studied in terms of income, diet, pollution exposure, length of time in the United States, psychosocial stressors and other factors," Leistikow said.

Leistikow said the new study yields three conclusions about Asian and Pacific Islander Americans: Smoke exposure can account for the vast disparities in cancer death rates among gender-ethnic groups; it can account for more than a third of the overall cancer death rate for females and the great majority of the male rate; and it may cause more non-lung than lung cancer deaths.

"In light of these findings, we believe tobacco control for Asian and Pacific Islander Americans, and probably other Americans, deserves more effort, funding, and study," Leistikow said.

In earlier studies, Leistikow and his colleagues reported similar associations between smoke exposure and non-lung cancer death rates in African American males. The non-lung cancer death rate is calculated by subtracting the age-adjusted lung cancer death rate from the mortality rate for all cancers.

In the new study, Leistikow and his colleagues found that Korean American males in California had the highest smoking-attributable cancer burden of any of the Asian and Pacific Islander American groups studied, with 71 percent of their cancer death rate linked to tobacco smoke exposure.

South Asian females in California had the lowest burden, with 0 percent of cancer deaths attributable to smoking. South Asians include people from India, Pakistan, Bangladesh, and Sri Lanka.

The researchers noted especially worrisome trends in three groups: South Asian males in California, whose lung cancer death rate doubled between 1988 and 2001, and Filipina and Korean females in California, whose lung cancer mortality has been climbing 4 to 5 percent per year.

"Based on our work, we can predict that these trends will be accompanied by parallel increases in non-lung cancer deaths," Leistikow said. "Many lives can be saved by strengthening tobacco control measures - cigarette taxes, counter-advertising, smoking bans, linguistically and culturally appropriate smoking prevention messages, and quit-smoking programs."