Non-vegetarian diet, poor sleep, obesity associated with increased risk of breast cancer: ICMR study

In India, breast cancer is one of the leading cancer sites, with an estimated 2,21,757 cases reported in 2022, accounting for close to a quarter (22.8%) of cancers in women.

New Delhi: Non-vegetarian diet, poor sleep and obesity have been associated with increased risk of breast cancer which is expected to rise by about 5.6 per cent annually leading to an estimated increase of 0.05 million new cases per year, according to an ICMR study.

Reproductive timing, hormonal exposure and family history also influence breast cancer risk primarily among Indian women, stated the study conducted by ICMR's National Centre for Disease Informatics and Research based in Bengaluru.

In 2022, an estimated 2.3 million women worldwide were newly diagnosed with breast cancer, resulting in approximately 670,000 deaths.

In India, breast cancer is one of the leading cancer sites, with an estimated 2,21,757 cases reported in 2022, accounting for close to a quarter (22.8 per cent) of cancers in women.

This study was a systematic review of the Indian studies assessing breast cancer risk factors among Indian women published up to December 22, 2024.

A meta-analysis using a random effects model estimated pooled associations between key risk factors and breast cancer.

Among the 1,871 articles identified, 31 studies met the inclusion criteria of which case-control studies were of moderate to high quality.

The study stated found that early menopause -- before 50 years -- showed an inverse association with breast cancer, whereas menopause after 50 years was associated with more than a twofold increase in risk.

Reproductive and hormonal factors, including age at marriage, pregnancy, abortion history, age at first and last childbirth, breastfeeding, oral contraceptive use, parity, and number of children were also examined.

The risk of breast cancer increased progressively with age at marriage.

Also. women reporting more than two induced abortions had 1.68 times higher risk compared to those with no abortions.

Late age at first childbirth (more than 30 years) showed markedly elevated risks. Breastfeeding duration was not significantly associated with breast cancer risk in most studies, and oral contraceptive use did not show a significant association, the study said.

Anthropometric findings indicate that abdominal obesity, measured by waist-to-hip ratio (more than or equal to 0.85), was more strongly associated with breast cancer risk than BMI, suggesting that fat distribution, rather than total body mass, may be more relevant for Indian women.

Lifestyle factors contributed significantly to breast cancer risk variability. A non-vegetarian diet was associated with increased risk, consistent with growing evidence on dietary fat intake and may be due to a higher intake of saturated fat and processed meats, which have been linked to estrogen production, the study said.

Similarly, poor sleep quality was also associated with increased risk. As evidence of circadian rhythm disruption in cancer development grows, these findings align with this growing body of evidence.

Findings from individual studies indicated that irregular sleep patterns and sleeping in a lighted room support the possible role of melatonin suppression in breast cancer development.

Elevated stress levels were also reported as significant in individual analyses, although variations in measurement tools and the predominance of cross-sectional designs limit causal interpretation, the study said.

Conversely, alcohol and tobacco use were not significantly associated with breast cancer risk, possibly reflecting low prevalence, underreporting, or population-specific biological differences.

The Collaborative Group on Hormonal Factors in Breast Cancer found in a large meta-analysis that alcohol consumption increases breast cancer risk by 7.1 % for every 10 g consumed.

Nevertheless, its contribution to breast cancer incidence in developing countries with low alcohol consumption (0.4 g/day) was negligible, and smoking had little to no independent effect.