NEW DELHI: Disrupted sleep, rising stress levels and central obesity are emerging as major drivers of India’s growing breast cancer burden, which is projected to rise by 5.6% annually and add nearly 50,000 new cases every year, according to a major new study by the ICMR-National Centre for Disease Informatics and Research.The systematic review and meta-analysis analysed Indian studies published up to Dec 22, 2024, to identify population-specific risk factors. Of nearly 1,900 scientific papers screened, 31 observational studies of moderate to high quality were included.Among lifestyle-related factors, individual studies showed a positive association between breast cancer risk and poor sleep quality, irregular sleep patterns, sleeping in illuminated rooms and high stress levels – reflecting the impact of urbanisation and changing work-life patterns. Regular physical activity, the researchers noted, was consistently associated with a lower risk.Central obesity was identified as a critical factor, with women having a waist-to-hip ratio of 0.85 or higher facing significantly elevated risk. Abdominal fat, researchers noted, plays a more decisive role than overall body weight, particularly among postmenopausal women.Clinicians say these lifestyle shifts are increasingly shaping breast cancer patterns in India. Dr Samit Purohit, director of medical oncology at Action Cancer Hospital, said breast cancer is no longer driven only by age or inherited risk. “Disrupted sleep cycles, chronic stress and central obesity are becoming silent but powerful contributors, as they alter hormonal balance, immune surveillance and inflammatory pathways,” he said, adding that irregular sleep suppresses melatonin-a hormone with protective anti-cancer properties-while chronic stress leads to sustained cortisol elevation and metabolic dysfunction.The meta-analysis also found strong links with reproductive and hormonal factors, including late menopause (after 50 years), delayed first pregnancy or childbirth (after 30), multiple abortions and higher age at marriage, all of which increase lifetime hormonal exposure. Family history of cancer, particularly breast cancer, emerged as one of the strongest predictors of risk.Researchers noted India’s breast cancer risk profile differs from Western populations, where hormone replacement therapy and early menarche are dominant factors. In India, the convergence of lifestyle disruption, reproductive delay and metabolic risk is reshaping disease patterns. The study called for large, population-based prospective cohort studies and stronger emphasis on prevention and early screening.