ABSTRACT
Purpose: Urbanization, obesity and ageing associated with lifestyle changes
(Westernized diet patterns, pollution, physical inactivity) have been proposed
as the major contributing factors for the global rise in breast cancer (BCa)
and have been the variables used to predict the future breast cancer rate. At
the same time, socio-economic level, instead of birth rate, has been proposed
for explanation of dramatic regional variations of breast cancer incidence. We
sought to determine which factor plays the determining role in predicting
worldwide breast cancer incidence rates and regional variations. Methods: Bivariate correlation was conducted to examine the relationships between
country-specific estimates of birth rate, BCa incidence, urbanization, overweight,
ageing and GDP. Partial correlation was performed to identify the correlation
between BCa incidence with each independent variable while we controlled the
other four variables. Multiple linear regression was used to identify the most
significant predictors of BCa incidence. Post hoc Scheff and independent T-Test
analysis were performed to compare mean differences in BCa incidence rates and
residuals of BCa standardised
on birth rate in the WHO regions, and UN developed and developing regions
respectively. Results: Worldwide, BCa incidence rate tends to increase
while birth rate decreases and urbanization, overweight, ageing and GDP
increase. However, birth rate was the only variable that had a significant
correlation with BCa incidence when controlled for the other four variables. Birth rate was the only significant predictor of
BCa incidence in regression analysis. Multiple mean differences of BCa
incidence between regions were significant, but all disappeared when the
contributing effect of birth rate on BCa incidence rate was removed. Conclusions: Birth rate plays a determining role in worldwide BCa incidence rate and
regional variations. Current BCa projection methods may estimate future rates
of BCa poorly if they fail to incorporate the impact of birth rate.