The effect of body fatness, lifestyle factors and gene-environmental interactions on the risk of female cancers among Asians

  • Topic: Combination of cancers
  • Institution: Provincial Centre for Disease Control and Prevention
  • Country: China
  • Status: Completed

Scientific abstract

(View plain language abstract)

Background

Female cancers have become important health issues in China. For breast cancer, although the crude incidence and mortality rates are still relatively low compared to western countries, such as the Netherlands, they have increased dramatically. Survival remains low in China. Ovarian cancer also shows a similar rising trend too.

Methods and results

Using an ecological study, significant correlations were found between age-specific body mass index (BMI), prevalence of overweight/obesity and incidence/mortality of breast cancer. A meta-analysis of 18 studies among Chinese women showed an 8% increase risk in breast cancer for each 1kg/m2 increase of BMI, (odds ratio (OR) =1.08, 95%CI: 1.04–1.11). Vehicle registration number was selected as indicator to examine the effect of economy development and ambient air pollution on breast cancer, significant correlations were observed (r=0.88 for incidence, r=0.94 for mortality), while Engel Coefficient was negatively correlated to breast cancer incidence with 5-year and 20-year lag (r=-0.88 and -0.89).

A population-based case-control study was conducted in Jiangsu province, China including 818 newly diagnosed breast cancer cases and 935 corresponding controls. Results demonstrated that, compared to normal women, high body fatness, estimated by high waist circumferences (≥ 90cm), obesity (BMI ≥ 28 kg/m2) and high waist-to-hip ratio (≥ 0.9) were associated with increased risk of breast cancer, OR was 2.85 (2.16–3.78), 1.70 (1.26–2.31) and 3.26 (2.35–4.52) respectively, and risks were higher among post-menopausal women. Moderate physical activities could decrease breast cancer risk among post-menopausal women (OR=0.59, 95% CI: 0.40–0.87). Unhealthy bra wearing (tight or sleeping with bra) and reproductive factors like long menstrual life (OR=5.88, 95% CI: 1.21–28.57), abnormal menstruation cycle (OR=2.05, 95% CI: 1.50–2.80) and use of estrogens (OR=1.96, 95% CI: 1.16–3.30) were positively associated with breast cancer.

A traditional Chinese dietary pattern (4th vs 1st quartile: pre-menopausal OR = 0.47, 95% CI: 0.29–0.76; post-menopausal OR = 0.68, 95% CI: 0.48–0.97), and consumption of bean products (OR for 1-49g/day = 0.50, 95% CI: 0.37–0.68; OR for ≥50g/day =0.36, 95% CI: 0.22–0.58, compared with non-eaters) may adversely affect breast cancer. Sleeping > 9 hours/day increased the risk (OR=2.32, 95% CI: 1.66–3.29), while insomnia moderately increased breast cancer occurrence (OR=1.46, 95% CI: 1.18–1.78). Several occupational or residential exposures to hazard factors were found to be potential risks, including high voltage line and water pollution enterprises nearby, occupational contact of toxic substances etc. Individual history of diabetes (OR=1.49, 95% CI: 1.04–2.12), benign breast diseases (fibroadenoma OR=1.76, CI: 1.12–2.76, breast cysts OR=2.09, CI: 1.09–4.04) and family history of breast cancer (OR=1.33, 95% CI: 1.03–1.73) were also significantly associated with breast cancer risk, while hereditary risk could be significantly enhanced by the presence of certain unhealthy lifestyles and high body fatness. Biochemical indexes, such as high serum lipids, elevated glucose (>7.0 mmol/L) (OR =1.87, 95% CI: 1.37–2.55) and high sensitivity C-reactive protein (>5 mg/L) (OR = 1.91, 95% CI: 1.20–3.06) increased breast cancer risk. Polymorphisms in genes such as vitamin D receptor rs11568820, obesity-related genes PPARG rs1175543 and CADM1 rs12286929 GA were also found to be associated with breast cancer risk. 

Conclusion

In conclusion, female cancers have been rising rapidly in China. The fast economic development causing significant lifestyle and environmental changes could be an underlying cause for this rise. We observed high body fatness, physical inactivity, unhealthy dietary patterns, sleeping habits, high blood glucose and lipids to be associated with breast cancer risk in China. Besides, hereditary determinants such as family cancer history and genetic polymorphisms may also influence individual susceptibility. As the majority of risk factors are modifiable, these findings could be translated into prevention programs to reduce the risk of breast cancer in China.

Plain language abstract

Background

Female cancers are becoming significant health problems in China; whether the same risk factors apply to these cancers in China as in western countries needs to be evaluated. Many studies have demonstrated the relationship between body fatness, lifestyle factors and breast cancer in Caucasians. However, the evidence among Chinese is not sufficient. Moreover, few studies have investigated the effect of body fatness, lifestyle factors, and their interactions with related genes on breast carcinogenesis in China.

Aims and objectives

We proposed a study in Jiangsu, a big province in China, aimed to:

  1. Further depict the epidemiological characteristics of major female cancers.
  2. Investigate the trends of breast cancer with population body fatness increase, economic growth and environmental change.
  3. Identify the effect of body fatness and lifestyle factors on breast cancer, as well as their interactions with related genes among Chinese women.

How the study was carried out

Population-based cancer registry data in Jiangsu and China were analysed to describe the incidence/mortality and time trends of breast cancer and ovarian cancer. A systematic literature review and meta-analysis was used to summarize the association between body fatness and breast cancer in studies conducted among Chinese women. An ecological study was conducted to study the relationship between trends in body fatness, economy growth, environmental change and breast cancer. In addition, a population-based case-control study was conducted including 818 new breast cancer cases and 935 controls in Jiangsu.

Key findings and conclusions

The incidence/mortality of breast cancer has increased dramatically in Jiangsu and China, while survival remains low. Ovarian cancer also shows a similar rising trend among Chinese women.

By an ecological study, significant correlations were found between incidence/mortality of breast cancer and BMI, overweight/obesity. Economic and environmental-related indices such as number of vehicles registered were also found positively related to breast cancer while Engel Coefficient was negatively correlated to incidence with lag.

Results of the case-control study demonstrated that high body fatness, including high waist circumference, high body mass index and high waist-to-hip ratio increased breast cancer risk, and risk was higher among post-menopausal women. Moderate physical activities decreased risk among post-menopausal women. Unhealthy bra wearing and reproductive factors like long menstrual life, abnormal menstruation cycle, use of oestrogens were positively associated with breast cancer. A traditional Chinese dietary pattern and high bean products intake may adversely affect breast cancer risk among Chinese women. Sleeping > 9 hours/day or insomnia would increase breast cancer occurrence. Residing close to a high voltage line and water pollution area, occupational contact of toxic substances etc were found to be potential risks. High serum lipids, elevated glucose (>7 mmol/L) and high sensitivity C-reactive protein (>5 mg/L) increased the risk of breast cancer. Hereditary risk could be significantly enlarged by unhealthy lifestyles and high body fatness. Inherited variants of genes encoding for obesity such as PPARG and CADM1, and the vitamin D receptor (VDR) were also found to be associated with breast cancer risk.

In conclusion, female cancers, mainly breast cancer, have been rising rapidly in China. The fast economic development and subsequent increase in body fatness, lifestyle and environmental changes could be the main reasons. Besides, hereditary determinants and polymorphisms of related genes may also influence individual susceptibility. As the majority of risk factors are modifiable, these findings could be translated into prevention programs to reduce the risk of breast cancer in China.

Grant publications