Overall Increase in Incidence Rates from 1975 to 2020

The breast cancer incidence rate among U.S. women has seen a general increase across all age groups from 1975 to 2020. Specifically, rates for women younger than 50 years increased from 40.7 to 46.8 per 100,000, rates for those aged 50 to 64 years rose from 233.2 to 264.2 per 100,000, and rates for those 65 years and older surged from 329.1 to 404.8 per 100,000.

Highest Recorded Incidence Rates by Age Group

The highest recorded incidence rates occurred in different years for each age group. For women younger than 50 years, the peak incidence rate was 49.7 per 100,000 in 2019. Women aged 50 to 64 experienced their highest rate of 295.3 per 100,000 in the same year, while the highest rate for those 65 years and older was 481.7 per 100,000 in 1998.

Notable Decade Shift around 2000

A significant shift in incidence rates around the year 2000 is evident, with most age groups experiencing a decline or stabilization in rates after years of steady increase. The incidence rates for women aged 65 years and older notably decreased from 481.7 per 100,000 in 1998 to 404.8 per 100,000 in 2020, reversing the previous upward trend.

Age Group with Steadiest Growth in Incidence Rates

Women aged 50 to 64 years exhibited the steadiest growth in breast cancer incidence rates over the 45-year span. This age group's rates increased from 233.2 per 100,000 in 1975 to 264.2 per 100,000 in 2020, with fewer fluctuations compared to the other age groups.

Impact of Age on Breast Cancer Incidence

Age significantly impacts breast cancer incidence rates. Throughout the data set, women aged 65 years and older consistently had the highest incidence rates, starting at 329.1 per 100,000 in 1975 and reaching 404.8 per 100,000 by 2020. This underscores the increased risk of breast cancer with advancing age.

Recent Trends Suggest a Potential Stabilization

Recent trends, particularly in the last decade from 2010 to 2020, suggest a potential stabilization in breast cancer incidence rates across all age groups. The increases have become more modest, with the younger than 50 years age group seeing an increase from 44.6 to 46.8 per 100,000, and the 50 to 64 years age group experiencing a decrease from 271.8 to 264.2 per 100,000.

Variability in Incidence Rates by Age Group

The variability in breast cancer incidence rates over time differs significantly by age group. The oldest age group (65 years and older) experienced the greatest fluctuation, with a peak rate of 481.7 per 100,000 in 1998 and the most substantial drop to 404.8 per 100,000 in 2020. Contrastingly, the youngest age group (younger than 50 years) showed more gradual changes over the years.