Childhood and teenage physical activity and breast cancer risk

Abstract

Purpose Adult physical activity is associated with reduced breast cancer risk, but few studies have evaluated activity before adulthood. Early life may be an important period because of rapid breast development and hormonal changes. This study contributes new information by examining childhood (age 5–12) and teenage (age 13–19) activity separately and overall. Methods The Sister Study is a cohort of 50,884 women aged 35–74. Women reported age 5–19 sports/exercise activities and age 10 and 16 unstructured activities. Both hours and MET-hours of activity were considered in association with breast cancer overall, by ER status, and menopausal status. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated with Cox proportional hazards models. Results 2,416 cases were diagnosed during follow-up (mean=6.4 years). Participation in 7+ hours (vs <1 hour) per week of sports/exercise during ages 5–19 was associated with reduced breast cancer risk (HR=0.75; 95% CI: 0.57–0.99). 7+ hours (vs <1 hour) per week of unstructured physical activity at age 16, but not age 10, was inversely associated with breast cancer (HR=0.81; 95% CI: 0.70–0.95). Associations were more pronounced for ER+ tumors, especially for activity during the childhood (age 5–12) period. Due to low correlation between childhood/teenage and adulthood activity in this study (r=0.1), it is unlikely that recent activity explains our results. Conclusions Findings from this large cohort indicate higher levels of physical activity during ages 5–19 are inversely associated with breast cancer risk, supporting early life as a window of susceptibility for breast cancer development.

Adult Physical Activity and Breast Cancer Risk in Women with a Family History of Breast Cancer

“…For the main associations, average hours/week and MET-hours/week were considered both continuously and categorically. Categorically, hours/week was examined as 0-<1, 1-<4, 4-<7, ≥7 hours per week which were chosen a priori as interpretable cut-points for public health recommendations and to be comparable with another study in this population (32), while MET-hours/week were categorized in quartiles. Outcomes considered were overall breast cancer, by menopausal status, and invasive breast cancer stratified by estrogen receptor (ER) status.…”

Physical Activity in Cancer Prevention and Survival: A Systematic Review

“…(14) Another study found that increased total, leisure, and occupational physical activity were inversely and significantly associated with reduced breast cancer risk. (15) One study found that increased physical activity in childhood and teenage years was associated with lower risk for breast cancer development, (16) while another found no association between physical activity between menarche and first pregnancy on later breast cancer risk. (17) Finally, a study found statistically significant associations between high versus low levels of physical activity and reduced risk for postmenopausal breast cancer.…”

Chemically induced carcinogenesis in rodent models of aging: assessing organismal resilience to genotoxic stressors in geroscience research

“…More recent experimental and epidemiological studies confirm that the peripubertal period, which is a time of rapid breast development (Haslam and Schwartz 2011;Olson et al 2010;Zhao et al 2013), is also an important window of susceptibility in which the breast cells might be especially vulnerable to potential carcinogens, endocrine disruptors, and endocrine changes, which affect the risk of breast cancer in later life (Biro and Deardorff 2013). For example, the NIEHS (National Institute of Environmental and Health Sciences) Sister Study, which examines environmental and familial risk factors for breast cancer in sisters of women who have had breast cancer, demonstrated that lifestyle factors (e.g., higher level of physical activity) around puberty influences breast cancer risk later in life (Niehoff et al 2017b). Animal studies support the concept that in addition to fetal exposure, the peripubertal period is also a susceptible window for epigenetic reprogramming, modulating risk for carcinogenesis.…”