Time-lag estimate between dietary intake and breast cancer mortality in Japan

This study examines the relationship between the nutrient intake, including total dietary fiber (TDF) and fat, and the age-adjusted mortality from breast cancer (MBC) in Japanese females during the period from 1948 to 2000. The information for MBC in females was based on the data in Vital Statistics of Japan. Nutritional data were collected from the National Nutrition Survey reports. The data were analyzed by Pearson's correlation and a partial correlation, adjusting for the effect of reproductive factors. The time lag was estimated by measuring the strength of the linear relationship set up for a 0-35-year delay in mortality and statistically evaluated by comparing the correlation coefficients. The partial correlation analysis indicated that the individual intakes of total fat (r=0.688), animal protein (r=0.657), carbohydrate (r=-0.886), and plant protein (r=0.770) were significantly (p<0.01) correlated with MBC. Each of these coefficients of correlation changed and reached a maximum value with increasing time lag. The estimated time lag values for the influence of fat, animal protein and TDF were 20-32 years, 19-31 years and 9-35 years, respectively. It is deduced from the results that the increased MBC in Japanese women is related to the long-term effect from the intake of a highfat, high-animal protein and low-fiber diet typical in the western world.