As a health educator and former pediatric nurse, Leona Pereza was glad she could also play a role in cancer research.

Pereza is one of the original participants in the Multiethnic Cohort Study — hailed as one of the most ethnically diverse epidemiologic studies in the world examining the roles that lifestyle, diet and other factors play in developing cancer and other chronic diseases.

When the University of Hawaii Cancer Center launched the study in 1993, it recruited more than 215,000 Hawaii and Los Angeles residents between the ages of 45 to 75 to participate and follow over time. Male and female participants represented five ethnic groups — Japanese, Native Hawaiian, African American, Latino and Caucasian.

Now, a quarter of a century later, more than 70 percent of those original participants are still involved with the study.

Some 500 from Hawaii, including a number of centenarians, gathered for the first time Saturday at UH Cancer Center for a 25th anniversary celebration.

“For 25 years now the MEC Study has continued to fulfill its mission to make a significant contribution to the goal of correcting cancer health disparities and preventing cancer and other chronic diseases in all populations,” UH Cancer Center director Randall Holcombe said in a news release. “We are proud to lead a study with such significant impact at the UH Cancer Center. The MEC study has gained national and international recognition among biomedical scientists, and is an example of the world-class research conducted at the University of Hawaii.”

The study has brought more than $150 million in federal research funding to UH, while its data has resulted in more than 600 published scientific articles on cancer-related studies.

Among the findings: a link between processed and grilled meat and cancer; and that drinking a cup of coffee a day can lead to a 12 percent decrease in risk of death from cancer and other diseases.

A noteworthy finding related to the diversity of the participants was that breast cancer survival is lower in obese women — regardless of ethnicity.

There are, however, ethnic disparities in other areas, the study has found. African-American and Native Hawaiian smokers have higher lung cancer risk, for instance, while Japanese Americans have high rates of colorectal cancer.

Looking at the differences across ethnic groups and understanding their causes helps scientists find new means of prevention, and leads to new branches of research, said epidemiologist and principal investigator Loic Le Marchand.

The study, founded by Dr. Laurence Kolonel at the UH Cancer Center and Dr. Brian Henderson at the University of Southern California Norris Cancer Center, recruited about 104,000 participants from Hawaii and 112,000 from California.

The participants initially filled out a 26-page questionnaire about their dietary habits, lifestyle and medical history, then were sent follow-up questionnaires every five years. Between 2001 and 2006, more than 70,000 participants also provided blood and urine samples, which remain in storage.

The National Cancer Institute has funded the study since its inception, and it is jointly conducted by the UH Cancer Center and Keck School of Medicine at USC.

The idea was to build upon a body of research among ethnic groups already done in Hawaii, according to Le Marchand.

“We had done a number of retrospective studies, and now we wanted to do something prospective, interview people before they developed cancer,” said Le Marchand. “We have had an excellent cancer registry in Hawaii since 1960, so we had many decades of good data on different groups and changes over time, and what was striking was those differences have remained.”

Breast cancer rates among Native Hawaiian, for example, are still higher than other ethnic groups, a pattern that has been in place since the 1970s, he said.

The study received a $15 million, five-year grant last year, according to Le Marchand, and will continue until 2022. He hopes it will continue another five to 10 years after that.

Besides playing a role in developing research at the UH Cancer Center, at least 100 graduate and post-­doctoral students have also used the data for training, he said. Some of the data is also shared with other institutions.

Pereza, 73, took a personal interest in cancer because it has affected her close family members. Her mother, maternal grandmother, and mother-in-law all died of breast cancer in their 70s.

“Knowing that once it occurs in your family, then you have increased chances of inheriting (breast cancer), plus being Native Hawaiian, there were a lot of odds against me,” said Pereza, a faculty member of the John A. Burns School of Medicine’s Maternal and Child Health Program. “I thought, well, I’ll be part of the study if I can help find an answer.”

Pereza said she hopes she never has to battle the breast cancer that has been part of her family history.

She lives a healthy lifestyle of regular exercise and a mostly vegetarian and whole grains diet. A runner for 40 years before she had to stop due to a hip injury, she is now training for a world competition in power lifting.

Like Pereza, Ron Staton also had a family member affected by cancer — his sister, who died from breast cancer a few years after the study began.

Staton, 79, a retired Associated Press journalist and former marathon runner, said that with so many people being affected by cancer, he was happy to do his small part. He had a malignant tumor removed from his leg just a year and a half ago, before it could reach other parts of his body.

Staton said he reads some of the scientific articles culled from the data from time to time, and that he appreciates the work of the UH Cancer Center.

Pereza said the studies have affirmed the lifestyle she values.

“If you can compare a healthy lifestyle and how the health status can be maintained over 25 years and if it correlates with what their findings are coming up with, then I think I’ve contributed as maybe a living example,” she said. “For me, it has affirmed my personal choices.”