In utero and childhood exposure to the Great Chinese Famine and risk of cancer in adulthood: the Kailuan Study

Early life exposure to Chinese famine and risk of digestive system cancer in midlife

To investigate whether early-life exposure to the Great Famine of 1959-1961 in China was associated with the risk of digestive system cancer. The prospective cohort study involved 17 997 participants from the Kailuan Study (Tangshan, China) that began in 2006. All participants were divided into three groups based on their date of birth. The unexposed group (born from 1 October 1962 to 30 September 1964), fetal-exposed group (born from 1 October 1959 to 30 December 1961), and early-childhood-exposed group (born from 1 October 1956 to 30 December 1958). The Cox proportional hazards model was used to analyze the association between early famine exposure and digestive system cancer. During the mean follow-up period of (10.4 ± 2.2) years, a total of 223 digestive system cancer events occurred. Including 54 cases in the unexposed group (62.14/100 000 person-years), 57 cases in the fetal-exposed group (114.8/100 000 person-years), and 112 cases in the early-childhood-exposure group (122.2/100 000 person-years). After adjusting covariates, compared with the unexposed group, the HR and 95% CI were 1.85 (1.28, 2.69) for participants in the fetal-exposed group and 1.92 (1.38, 2.66) for participants in the early-childhood-exposed group. No interactions were observed in our study. After classifying digestive system cancers, the HR and 95% CI were 2.02 (1.03, 3.97) for colorectal cancer for participants in the fetal-exposed group and 2.55 (1.43, 4.55) for participants in the early-childhood-exposed group. The HR and 95% CI were (1.13, 3.83) of liver cancer for participants in the fetal-exposed group and 1.15 (0.63, 2.10) for participants in the early-childhood-exposed group. Early-life famine exposure was associated with a higher risk of digestive system cancer in adulthood. Fetal-exposed individuals might increase the risk of colorectal cancer and liver cancer, and early childhood-exposed might increase the risk of colorectal cancer.

Early-life exposure to the Great Chinese Famine and gut microbiome disruption across adulthood for type 2 diabetes: three population-based cohort studies

BACKGROUND

The early life stage is critical for the gut microbiota establishment and development. We aimed to investigate the lifelong impact of famine exposure during early life on the adult gut microbial ecosystem and examine the association of famine-induced disturbance in gut microbiota with type 2 diabetes.

METHODS

We profiled the gut microbial composition among 11,513 adults (18-97 years) from three independent cohorts and examined the association of famine exposure during early life with alterations of adult gut microbial diversity and composition. We performed co-abundance network analyses to identify keystone taxa in the three cohorts and constructed an index with the shared keystone taxa across the three cohorts. Among each cohort, we used linear regression to examine the association of famine exposure during early life with the keystone taxa index and assessed the correlation between the keystone taxa index and type 2 diabetes using logistic regression adjusted for potential confounders. We combined the effect estimates from the three cohorts using random-effects meta-analysis.

RESULTS

Compared with the no-exposed control group (born during 1962-1964), participants who were exposed to the famine during the first 1000 days of life (born in 1959) had consistently lower gut microbial alpha diversity and alterations in the gut microbial community during adulthood across the three cohorts. Compared with the no-exposed control group, participants who were exposed to famine during the first 1000 days of life were associated with consistently lower levels of keystone taxa index in the three cohorts (pooled beta - 0.29, 95% CI - 0.43, - 0.15). Per 1-standard deviation increment in the keystone taxa index was associated with a 13% lower risk of type 2 diabetes (pooled odds ratio 0.87, 95% CI 0.80, 0.93), with consistent results across three individual cohorts.

CONCLUSIONS

These findings reveal a potential role of the gut microbiota in the developmental origins of health and disease (DOHaD) hypothesis, deepening our understanding about the etiology of type 2 diabetes.

Famine Exposure during Early Life and Risk of Cancer in Adulthood: A Systematic Review and Meta-Analysis

OBJECTIVES

Emerging evidences have explored the association between famine exposure during early life and cancer risk in adulthood, but the results remain controversial and inconsistent. This study aimed to provide a comprehensive evidence on the relation of famine exposure to later cancer risk.

DESIGN

Systematic review and meta-analysis.

METHODS

Relevant reports published up to March, 2022 were identified by searching PubMed, Embase, Web of sciences and Medline databases. Pooled relative ratios (RRs) with 95% confidence intervals (CIs) were used to evaluate the effect famine exposure on cancer risk.

RESULTS

Totally, 18 published articles with 6,061,147 subjects were included in this study. Compared with unexposed group, early life famine exposure dramatically increased the risk of cancer in adulthood (RR=1.13, 95% CI: 1.04-1.22). The pooled RRs were different in terms of sex, exposure severity, exposure period, famine type, study design type and cancer location. A remarkably elevated risk for cancer was discerned in women exposed to famine (RR=1.09, 95% CI: 1.00-1.18), severe exposure (RR=1.12, 95% CI: 1.02-1.22) and adolescence exposure (RR=1.76, 95% CI: 1.02-2.50), Chinese famine exposure (RR=1.55, 95% CI: 1.29-1.82) and cohort studies (RR=1.28, 95% CI: 1.13-1.42). Moreover, a significant association of early-life famine exposure with increased risk of breast (RR=1.16, 95% CI: 1.05-1.27) and stomach cancers (RR=1.89, 95% CI: 1.24-2.54) was observed.

CONCLUSION

This meta-analysis suggests that exposure to famine during early life may increase the risk of cancer in adulthood. The above-mentioned association is pronounced in women exposed to famine, severe exposure, adolescence exposure, Chinese famine, cohort studies, breast and stomach cancers. It is essential for decision-makers to take targeted measures for improving population awareness regarding the long-term effect of early life nutritional status.

Is it just a cure? Re-evaluating the effects of prenatal exposure to the Great Chinese Famine on the risk of infectious diseases in adulthood

BACKGROUND

Very limited studies focused on the early-life adversities on infectious diseases. Taking the Great Chinese famine as a natural experiment, this study re-evaluated the long-term effect of prenatal famine exposure on infectious diseases by using nationally representative data.

METHODS

Using difference-in-difference (DID) models, we analyzed 215,216 adults who participated in the Second National Sample Survey on Disability in 2006 across 734 counties of China to detect the effects of prenatal exposure to the Great Chinese Famine on the risk of infectious diseases in adulthood. Infectious diseases were ascertained by using the combination of self-reports or family members' reports and on-site medical diagnosis by experienced specialists, and the severity of famine was measured by the cohort size shrinkage index (CSSI) at the county level.

RESULTS

All DID estimates of the effects of famine on the probability of infectious diseases were insignificant, with a coefficient of 0.0007 (-0.0024, 0.0026) for all participants and coefficients of 0.0001 (-0.0041, 0.0043) and -0.0002 (-0.0036, 0.0033) for males and females, respectively. That is, the famine cohort dwelling in regions with a greater intensity of famine had similar levels of infectious disease risks than the cohorts with post-famine prenatal exposure experience in less affected famine regions. Furthermore, there were no significant famine and post-famine cohort differences in the DID estimates by examining the variations in subgroups with different types of infectious diseases (trachoma, poliomyelitis, tuberculosis, maternal infections and other infectious diseases).

CONCLUSION

No significant impact of prenatal exposure to the Chinese famine was observed on the risk of infectious diseases in adulthood. Famine survivors may be "cured" by the famine and were resilient to adverse environments in their life course because selective mortality may weaken the association between adverse prenatal exposure and later health.

Early-Life Exposure to the Chinese Famine of 1959-1961 and Type 2 Diabetes in Adulthood: A Systematic Review and Meta-Analysis

BACKGROUND

The fast-growing literature suggests that the Chinese famine of 1959-1961 drives current and future type 2 diabetes (T2D) epidemics in China. This conclusion may be premature, as many Chinese famine studies have major methodological problems. We examine these problems, demonstrate how they bias the study results, and formulate recommendations to improve the quality of future studies.

METHODS

We searched English and Chinese databases for studies that examined the relationship between prenatal exposure to the Chinese famine and adult T2D from inception to 8 February 2022. We extracted information on T2D cases and study populations of individuals born during the famine (famine births), before the famine (prefamine births), and after the famine (postfamine births). We used random-effects models to compare the odds of T2D in famine births to several control groups, including postfamine births, combined pre- and postfamine births, and prefamine births. We used meta-regressions to examine the impacts of age differences between comparison groups on famine effect estimates and the role of other characteristics, including participant sex, age, and T2D assessments; famine intensity; residence; and publication language. Potential sources of heterogeneity and study quality were also evaluated.

RESULTS

Twenty-three studies met our inclusion criteria. The sample sizes ranged from less than 300 to more than 360,000 participants. All studies defined the famine exposure based on the participants' dates of birth, and 18 studies compared famine births and postfamine births to estimate famine effects on T2D. The famine and postfamine births had an age difference of three years or more in all studies. The estimates of the famine effect varied by the selection of controls. Using postfamine births as controls, the OR for T2D among famine births was 1.50 (95% CI 1.34-1.68); using combined pre- and postfamine births as controls, the OR was 1.12 (95% CI 1.02-1.24); using prefamine births as controls, the OR was 0.89 (95% CI 0.79-1.00). The meta-regressions further showed that the famine effect estimates increased by over 1.05 times with each one-year increase in ignored age differences between famine births and controls. Other newly identified methodological problems included the poorly assessed famine intensity, unsuitable study settings for famine research, and poor confounding adjustment.

INTERPRETATION

The current estimates of a positive relationship between prenatal exposure to the Chinese famine and adult T2D are mainly driven by uncontrolled age differences between famine births and postfamine births. Studies with more rigorous methods, including age-balanced controls and robust famine intensity measures, are needed to quantify to what extent the famine exposure is related to current T2D patterns in China.