Why is the prevalence of abnormal uterine bleeding (AUB) lowest in women aged 40–45 and highest in women aged 46–50 in our study?

Explanation of Age-Related AUB Prevalence Pattern

Your finding of lowest AUB prevalence at ages 40-45 and highest at 46-50 reflects the physiological transition into perimenopause, where hormonal instability peaks in the late perimenopausal period before menopause, causing maximal menstrual irregularity and bleeding disturbances.

Hormonal and Physiological Basis

The pattern you observed aligns with established perimenopausal physiology:

• Ages 40-45 represent early perimenopause where ovulatory cycles are still relatively preserved, though beginning to show irregularity. Women in this age bracket maintain more consistent estrogen-progesterone balance compared to older perimenopausal women 1.

• Ages 46-50 represent late perimenopause where anovulatory cycles become predominant. This creates unopposed estrogen exposure leading to endometrial proliferation, irregular shedding, and increased bleeding episodes. The hormonal chaos of this transition period directly manifests as AUB 2.

Supporting Evidence from the Literature

Multiple studies confirm age-specific patterns in AUB presentation:

• The largest study examining 3,006 premenopausal women with AUB found that women aged 45-50 had significantly higher rates of pathological findings compared to younger age groups, with odds ratios of 3.85 for atypical hyperplasia and 4.03 for carcinoma when compared to women under 45 1.

• A 2024 analysis of 462 perimenopausal women demonstrated that the 51-55 age group had significantly higher prevalence of atypical endometrial hyperplasia and endometrial cancer compared to both the 40-45 and 46-50 age groups (P < 0.05), suggesting a progressive increase in pathological risk as women approach menopause 2.

• Research consistently shows that the 41-50 age bracket represents the peak presentation period for AUB overall, with 33.5% of all AUB cases occurring in this decade 3.

Clinical Implications of Your Finding

Your observation has important clinical ramifications:

Increased vigilance is warranted for the 46-50 age group because:

• This age bracket experiences maximal hormonal fluctuation
• Risk of endometrial pathology (hyperplasia, carcinoma) increases substantially
• The 45-year threshold is widely recognized as the cutoff for mandatory endometrial sampling in women with AUB 1

The relative "quiet period" at ages 40-45 likely represents:

• Residual ovarian reserve maintaining more regular cycles
• Lower cumulative estrogen exposure compared to older perimenopausal women
• Fewer anovulatory cycles compared to the 46-50 cohort

Common Pitfalls to Avoid

When interpreting age-related AUB patterns:

• Do not assume benign etiology based solely on age - even in the 40-45 group, irregular bleeding (rather than cyclical heavy bleeding) warrants endometrial investigation regardless of age 1

• Recognize that structural causes vary by age - younger reproductive women more commonly have ovarian cysts and uterine enlargement, while the perimenopausal/menopausal transition sees increased fibroids and endometrial pathology 4

• Body mass index and metabolic factors compound age-related risk - diabetes and obesity progressively increase with age and correlate with advancing endometrial pathology 2

Pattern Recognition

The age-specific distribution you identified follows this trajectory:

1. Ages 40-45: Relatively preserved ovulatory function → lower AUB prevalence
2. Ages 46-50: Peak hormonal instability and anovulation → highest AUB prevalence
3. Ages 51+: Post-menopausal stabilization (though with highest malignancy risk when bleeding occurs)

This U-shaped or progressive pattern reflects the natural history of ovarian senescence and its impact on endometrial stability. Your data captures the critical perimenopausal window where bleeding disorders peak before the eventual cessation of menses.