HONOLULU -- The National Children's Study announced on Thursday that Hawaii has become a part of the largest study in U.S. history on children's health.

The study will involved 100,000 families. Researchers hope to learn more about what causes childhood diseases and how to prevent them.

Taylor Watanabe is normally a happy child, but her life turns upside down when she gets sick with coughs.

"Because she recently started preschool, she's sick quite often. So, doctors are treating her for early signs of asthma," Taylor's mother, Haven, said.

A new study could one day help children like Taylor. The National Children's Study announced that Hawaii will be one of 22 study centers in the country to look at children's health.

"We are thrilled Honolulu County is going to be one of the counties studied," said Dr. Lynnae Sauvage from the University of Hawaii's John A. Burns School of Medicine.

Sauvage will lead the study that will follow 1,000 children from Oahu over 21 years.

"This is I think the most important study in maternal child health of this century because of the very large sample size," Sauvage said.

Researchers will study the nation's most pressing childhood diseases including diabetes, obesity and asthma.

They will track the children before they are even born. The state, local hospitals and health care professionals will try to recruit women who are pregnant or likely to have a child to participate in the two-decade study, which starts in 2009.

Researchers plan to release initial results after the first year.