While a number of breast cancer risk factors have been identified, little emphasis has been placed on factors driving breast cancer that occurs before age 50 but not at a young age (under 40). Based on available evidence to date, childhood obesity appears to be protective against breast cancer until perimenopause, for reasons that are not well understood.
It is the thin girls who go on to have the highest rates of premenopausal breast cancer. However, when obese younger women do develop breast cancer, obesity appears to contribute to more aggressive disease with unfavorable prognosis. Now a new Finnish study has identified the main risk factors for breast cancer diagnosed during ages 40 to 49, among them obesity.
Latest research describes risk factors for age 40-50 BC
The study referenced above was designed to investigate the role of lifestyle drivers of increases in breast cancer in Finish women ages 40 to 50 years (defined in the study as early-onset breast cancer). To conduct the study, the authors analyzed data from six health-related studies during the period 1972–2015 in combination with breast cancer data from the Finnish Cancer Registry. The study included 56,253 women, of whom 397 were diagnosed with early-onset breast cancer and 53 were diagnosed under age 40.
The authors carefully considered the following possible drivers of the increase in early-onset breast cancer observed in recent years: age at menarche, age at first birth or nulliparity, use of hormonal contraceptives, alcohol consumption, level of education, level of physical activity, obesity, current smoking and/or exposure to second-hand smoke.
Among the early-onset breast cancer patients, the highest annual increase in age-standardized breast cancer incidence was found among those who were overweight (average annual percent change (AAPC) = 4.0%), currently smoking (AAPC = 3.3%), or only moderately rather than highly physically active (AAPC = 2.9%). No such change by risk factors was seen in women diagnosed under 40 years of age.
The authors summarize that the increase in breast cancer incidence was highest among women aged 40–49 who were overweight, currently smoking, or only moderately physically active, whereas no change according to risk factors was found in women under 40. The study results highlight the importance of lifestyle risk factors in early-onset breast cancer and suggests that the cancer development process is different in young adults.