Diet, sleep and obesity linked to rising breast cancer risk among Indian women: ICMR study

Poor sleep, a non-vegetarian diet and abdominal obesity are emerging as key contributors to breast cancer risk among Indian women, with cases projected to rise by about 5.6 per cent annually, an analysis by the Indian Council of Medical Research has found.

The study estimates that this trend could translate into roughly 0.05 million additional new cases every year. Breast cancer is already among the leading cancers affecting women in India, with 2,21,757 cases reported in 2022 — nearly 23 per cent of all cancers in women.

Conducted by ICMR’s National Centre for Disease Informatics and Research in Bengaluru, the review assessed Indian studies published up to December 22, 2024, examining risk factors specific to Indian women. Researchers screened 1,871 articles, of which 31 studies — largely moderate- to high-quality case-control studies — met the inclusion criteria. A random-effects meta-analysis was used to estimate pooled associations.

Globally, breast cancer remains the most common cancer among women. In 2022, around 2.3 million women were diagnosed worldwide, and about 670,000 died from the disease.

The analysis highlighted the role of reproductive and hormonal factors. Menopause after the age of 50 was associated with more than a twofold increase in breast cancer risk, while early menopause, before 50, showed an inverse association. Risk also rose steadily with increasing age at marriage. Women reporting more than two induced abortions had a 1.68 times higher risk compared to those with none, and the first childbirth after 30 years of age was linked to a markedly elevated risk.

Breastfeeding duration did not show a consistent association with breast cancer risk across most studies. Use of oral contraceptives was also not found to have a significant link.

Body fat distribution emerged as a stronger predictor than overall body weight. Abdominal obesity, measured through a waist-to-hip ratio of 0.85 or higher, was more strongly associated with breast cancer than body mass index, suggesting that where fat is stored may matter more than total body mass for Indian women.

Lifestyle factors showed notable effects. A non-vegetarian diet was linked to increased risk, which researchers said may be due to higher intake of saturated fats and processed meats associated with estrogen production. Poor sleep quality was also associated with higher risk, aligning with growing evidence on circadian rhythm disruption and cancer development. Individual studies pointed to irregular sleep patterns and sleeping in lighted rooms, supporting the possible role of melatonin suppression.

Elevated stress levels were reported as significant in some analyses, though researchers cautioned that variations in how stress was measured and the reliance on cross-sectional study designs limit firm conclusions.

Alcohol and tobacco use were not significantly associated with breast cancer risk in the Indian studies reviewed. The researchers noted that this may reflect low consumption levels, underreporting or population-specific biological factors. They cited earlier international evidence showing alcohol increases breast cancer risk by about 7 per cent for every 10 grams consumed, but said its overall contribution in countries with very low average intake, such as India, is likely to be minimal.

The findings underscore the growing importance of lifestyle and metabolic factors in shaping breast cancer risk in India, alongside established reproductive and genetic influences.