Kaiser Permanente launched a survey of its Northern California membership Wednesday in the first phase of an ambitious multiyear study into the genetics and lifestyle factors that give rise to common diseases.

Researchers said the project could last 50 years and draw information from 500,000 adult health plan members who agree to participate — making this potentially the biggest study of its kind in the United States and one of the biggest in the world.

It could help produce a new model of individualized medicine geared to DNA profiles.