Therefore, menarche-to-first pregnancy represents a window of time when breast tissue is particularly vulnerable to carcinogenic stimuli. The longer the interval between menarche and first pregnancy the greater is a woman’s breast cancer risk.Breast cancer risk increased by a factor of 1.050 for every year younger at menarche. Early AAM ≤12 vs ≥ 14 is associated with increased risk of young-onset breast cancer and invasive breast cancer. AAM is a well-established breast cancer risk factor.Adverse childhood experience, such as sexual abuse, alcohol addicted or nervous troubled parents are strongly associated with early AAM.Physical activity and nutritional deficiency influences AAM and lead to, an average, 1-year delay in AAM.
Girls exposed to regular high intensive physical exercises in childhood and adolescence delay AAM.On the other hand, vegetable protein, fiber and vitamin D protect against rapid AAM. Consuming animal protein (cow milk and meat) and soy-containing products promote early AAM through excessive energy intake and subsequent overweight.A strong association between large waist circumference and early AAM has more predictive value than body weight for possible adverse outcomes in adulthood. Higher body mass index (BMI) in girls as young as 36 months of age is associated to early menarche.Menarche tends to be earlier in girls with more body fat and later in girls who exercise. Non-hereditary factors like a childhood diet that is high in animal protein and low in vegetable protein may also be linked with earlier menarche. The contribution of genetic factors is about 57-82%. Age at menarche is determined in part by hereditary and non-hereditary factors.
The AAM for Asian girls is 13.00 ± 1.26 years.