Rationale, design, and profile of the Three-Prefecture Cohort in Japan: A 15-year follow-up.

Background: We reutilized the existing Three-Prefecture Cohort to evaluate the relationship between lifestyle factors and the incidence or mortality from non-communicable diseases.

Methods: This study was a prospective population-based observation conducted from the 1980s to 2000 in three prefectures (Miyagi, Aichi, and Osaka) in Japan. The study subjects were residents aged ≥40 years who received a questionnaire. The follow-up period was 15 years from the baseline survey in each study area. A self-administered questionnaire, which included items on participants' demographic factors and lifestyle characteristics, was administered. Vital status and date of death were collected from residence certificates by the local government, and cause of death was identified using vital statistics. Cancer incidence and the date of diagnosis were collected from local cancer registry data.

Results: A total of 46,421 men and 54,189 women were eligible for our analysis. The person-years of follow-up for cancer incidence were 464,664 and 567,271 for men and women, respectively, and those for death were 527,940 and 648,601 for men and women, respectively. There were 8479 cancer incidences (5106 men and 3373 women) and 20,240 total deaths (11,156 men and 9084 women). The stomach was the most common cancer incidence site for both men (25.6%) and women (18.6%). The leading cause of death was cancer among men (35.0%) and cardiovascular disease among women (41.0%).

Conclusions: The Three-Prefecture Cohort Study enabled us to reveal the association of multiphasic lifestyle factors with cancer incidence and mortality. The study will also allow us to conduct a pooled analysis in combination with other large-scale cohorts.