Scientists for decades have lumped Asians into one homogenous group when studying conditions like breast cancer and heart disease, leading to false conclusions that don't take into account the health disparities among different nationalities, researchers now say. In fact, sub groups of Asians and Pacific Islanders can face dramatically different risks for developing certain diseases. One recent study found that Hmong adults in California have rates of liver and cervical cancer three to four times higher than those of other Asians and Pacific Islanders, for example. And communities often vary wildly when it comes to preventive care and survival rates. The same study noted that Hmong residents were less likely than other Asians to get immunizations that can prevent both types of cancer. To address some of these variances, the American Journal of Public Health on Thursday published its first issue devoted to health care in Asian and Pacific Islander populations. 'Because of the way the data has been framed in the past, when you group everyone together you don't see the disparities,' said Marguerite Ro, deputy director of the Asian and Pacific Islander American Health Forum in San Francisco. 'Some of the data coming out is the first data we've ever gotten on these groups. 'What we need to do now is point out disparities and not continue to make assumptions and base resource allocations on stereotypes.' Breast cancer has long been considered less of a problem for Asian women than for any other ethnic group. That's true for Asian women as a group, but when Bay Area researcher Scarlett Lin Gomez divided Asians into different nationalities, she found that Japanese women have rates of disease similar to white women. Disease rates didn't just vary by nationality; whether a woman was born in the United States or in another country was also a factor. U.S.-born Chinese and Filipina women under age 55 actually had higher rates of breast cancer than white women of the same age, Gomez said. The study looked at more than 20,000 breast cancer cases among six Asian ethnic groups from 1998 to 2004. 'You constantly hear not all Asians are alike, and these results really do play to that message,' said Gomez, a research scientist with the Cancer Prevention Institute of California in Fremont. 'All too often you hear stories of women who go to their doctors, and they say you have nothing to worry about because Asian women don't get breast cancer. This data is powerful and debunks that myth that disease isn't a problem in this population.' Research into heart disease also has suffered from lumping Asians together. Asian American adults as a group are 50 percent less likely to die from heart disease than white adults, according to one study published in Thursday's public health journal. But Native Hawaiian and Pacific Islander adults, who are often included with Asians in health studies, are 40 percent more likely to be diagnosed with heart disease than white adults. On the preventive side, Bang Hai Nguyen, a research scientist with the Cancer Prevention Institute, published a study in the journal looking at ways to improve screening for colorectal cancer in Vietnamese adults. People who were exposed to a simple public health campaign targeting Vietnamese communities were 1.4 times more likely to get screened for colorectal cancer than those who didn't have access to the same materials, Nguyen said. It might seem obvious -- target a certain population and you'd expect those people to respond -- but for decades, sub groups of Asians have been ignored in larger public health campaigns, he said. 'The Asian and Pacific Islander community is very diverse. They range from very recent immigrants, such as Vietnamese, to fifth- and sixth-generation Japanese American or Chinese American,' Nguyen said. 'Each of these ethnic groups also has particular needs and languages and cultures. If you are just reaching out in one language, you're not really reaching everyone.' 