Incidence of breast cancer in Chinese women exposed to the 1959-1961 great Chinese famine

Abstract

Background: The association of malnutrition in early life with breast cancer risk has been studied in Europe by investigating survivors of the Dutch Hunger Winter Famine, but not in China. We evaluated the effect of exposure to the 1959-1961 Great Leap Forward famine on subsequent breast cancer risk in Chinese women.

Methods: A total of 59,060 women born in 1955~1966 were recruited from Minhang district, Shanghai, China, during the period 2008 to 2012. A baseline survey was conducted to collect demographic characteristics and known risk factors for breast cancer. Incident breast cancers were identified by conducting record linkage with the Shanghai Cancer Registry up to June 30, 2015, and confirmed through medical records. Cumulative probabilities of cancer incidence were evaluated after adjusting for age, educational level and other confounders. Cox regression models were applied to estimate the hazard ratios (HR) and 95% confidence intervals (CI) of breast cancer.

Results: The overall crude incidence of in situ and invasive breast cancer were 19.2 and 115.0 per 100,000, respectively, in women conceived or born during the famine (1959-1962), slightly higher than those in women born before (1955-1958) (13.2 and 109.8/100,000) and after (1963-1966) (10.4 and 101.5/100,000). Particularly, at age group of 50-52 years when all participants contributed person-year of observations, the age-specific incidence of invasive breast cancer was higher in pre-natal exposed women (123.7/100,000, 95%CI: 94.5-161.9/100,000) than in post-natal exposed (109.6/100,000, 95%CI: 69.1-174.0/100,000) and unexposed women (82.7/100,000, 95%CI: 46.9-145.7/100,000). However, the incidence of cancer in situ was slightly lower in pre-natal exposed women at the age group. Adjusted cumulative probabilities of breast cancer incidence, both in-situ and invasive, were also observed to be higher in women exposed to the famine, however, the difference was not statistically significant.

Conclusion: Our results suggest a possible adverse, but limited, impact of exposure to the Great famine on the risk of breast cancer in Chinese women.

Keywords: Breast cancer; Chinese women; Incidence; The great leap forward famine.

Fig. 1

Cumulative probabilities of invasive breast cancer incidence by birth year in Chinese women. Adjusted for age (as a continuous variable), educational level (Primary school or below / Middle School / Technical school / High school / College or above, dummy variables), age at menarche (<12 / ≥12 years old), regular menstrual cycle (yes / no) estrogen use (ever / never) and family history of breast cancer (ever / never)

Fig. 2

Cumulative probabilities of breast cancer in situ incidence by birth year in Chinese women. Adjusted for age (as a continuous variable), educational level (Primary school or below / Middle School / Technical school / High school / College or above, dummy variables), in marriage (yes / no), regular menstrual cycle (yes / no), breastfeeding (ever / never) and family history of breast cancer (ever / never)