Is follicular atresia biphasic?

Area of Science:

• Reproductive biology
• Ovarian physiology
• Biostatistics

Background:

• Human oocyte depletion is a critical factor in female reproductive aging.
• Previous interpretations suggested a biphasic pattern of follicular atresia around age 38, linked to decreased fecundability and increased chromosomal abnormalities.
• Log-linear plots are commonly used to model biological decay rates.

Purpose of the Study:

• To critically evaluate the rate of human follicular depletion.
• To investigate the interpretation of curved scatters observed on log-linear plots of follicular depletion data.
• To determine if there is a biological basis for an accelerated rate of follicle loss around age 38.

Main Methods:

• Analysis of published autopsy and histologic data on human ovaries.
• Application and comparison of four distinct mathematical models to the follicular depletion data.
• Examination of data on original measurement scales and log-linear transformed scales.

Main Results:

• Human oocyte depletion data do not support a biphasic follicular atresia model.
• No significant perturbation in follicle loss rates was observed between ages 37 and 40.
• The instantaneous rate of follicle loss is lower after age 40 than previously suggested.

Conclusions:

• There is no evidence of an abrupt increase in follicular atresia rate around age 38.
• The perceived acceleration in follicular depletion is an artifact of log-linear transformation, not a biological phenomenon.
• Reproductive aging and associated risks should be interpreted based on non-transformed data for accuracy.