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).
Immune cycle Immune cycle The immune cycle is a natural homeostatic oscillation of the immune system when chronic inflammation is occurring. Similar to the menstrual cycle, the exact wavelength and waveform of each particular individual patient is different. That is, different people have different immune cycles although each cycle is typically repeated every seven days. C-reactive protein levels in the blood need to be measured every few days in order to have enough time points to show a repeating fluctuation (a wave-like cycle). This is caused by the synchronous division of T cells over time, with T-effector cells boosting immune activity followed