Menstrual cycle shortest and longest cycle lengths is considered very irregular. The average menstrual cycle lasts 28 days. The variability of menstrual cycle lengths is highest for women under 25 years of age and is lowest, that is, most regular, for ages 25 to 39. Subsequently, the variability increases slightly for women aged 40 to 44. The luteal phase of the menstrual cycle is about the same length in most individuals (mean 14.13 days, standard deviation 1.41 days) whereas the follicular phase tends to show much more variability (log-normally distributed with 95% of individuals having follicular phases between 10.3 and 16.3 days).
Centre for Menstrual Cycle and Ovulation Research stated that its research shows overall that regular menstrual cycles with ovulation help prevent osteoporosis, breast cancer, and heart disease. Dr. Prior has called menstrual cycles "a vital sign". CeMCOR does not conduct research funded by the pharmaceutical industry. Centre for Menstrual Cycle and Ovulation Research The Centre for Menstrual Cycle and Ovulation Research (CeMCOR) is a health research centre in Vancouver. According to the University of British Columbia, CeMCOR is the only centre in the world that focuses on ovulation and the causes and consequences of ovulation disturbances. CeMCOR is known for research on progesterone-only therapy for menopausal hot