Age and sex do not explain territorial disparities in colorectal cancer screening

Introduction

The Barcelona Colorectal Cancer Screening Program offers biennial Fecal Immunochemical Testing (FIT) to 400,000 residents aged 50–69. Analysis by Primary Healthcare Areas (PHAs) reveals territorial and temporal disparities in participation and positivity rates. These variations may stem from demographic structures, as both indicators vary by age and sex. This study aims to standardize these indicators to improve comparability across territories and evaluate the real influence of demographic variables on observed disparities.

Methods

Direct and indirect standardization methods were applied, using the program’s 7th round (2022–2023) as a reference. Standardized participation and FIT positivity rates were calculated for all PHAs across three consecutive biennial rounds (2018–2023).

Results

Directly standardized participation rates were higher in PHAs with younger populations and more men—groups with lower baseline uptake. However, the difference between crude and standardized rates did not exceed 1.7%, and significant territorial disparities persisted, with adjusted values ranging from 29% to 60%. Direct standardization also increased FIT positivity in younger, male-dominated areas, though the maximum increase was only 0.24 percentage points, with wide territorial variability remaining (2.8% to 6.8%). Through indirect standardization, we estimated expected participation between 47.3% and 50.2%, a much narrower range than observed rates. Expected positivity also showed minimal variation, oscillating between 4.05% and 4.2%.

Conclusions

The high similarity between crude and standardized rates indicates that territorial differences are not primarily driven by demographic structure, but likely stem from contextual factors and socioeconomic determinants.

Key messages

• Age and sex standardization does not explain the wide territorial gaps in screening participation, suggesting that demographic structure is not the primary driver of these health inequities.

• The persistence of disparities after adjustment indicates that socioeconomic and contextual factors, rather than population age or sex, are the main determinants of screening performance.