Colonoscopy Beyond 75: Risks May Outweigh Benefits for Average-Risk Patients

Colorectal cancer (CRC) screening has demonstrably reduced incidence and mortality through early detection and removal of precancerous lesions.¹ Guidelines from organisations such as the US Preventive Services Task Force (USPSTF) recommend screening for average-risk individuals up to age 75.² For those aged 76 to 85, the decision to screen is individualised, based on patient preferences, life expectancy, comorbidities, and prior screening history.² Beyond 85 years, screening is generally not recommended.² This nuanced approach for older adults reflects a recognition that the balance of benefits and harms shifts with advancing age.

The primary benefit of colonoscopy is the detection and removal of adenomatous polyps, which are precursors to CRC, and the identification of early-stage cancers.¹ However, the natural history of CRC in older adults can be slower, and the lead time bias associated with screening may mean that some cancers detected in very elderly individuals would not have become clinically significant during their remaining lifespan.³ Furthermore, the time required for an adenoma to progress to invasive cancer is typically 5 to 10 years, meaning that individuals with a limited life expectancy may not accrue the full benefit of polyp removal.³

Procedural Risks and Outcomes in Older Adults

The risks associated with colonoscopy, while generally low in younger, healthier populations, increase with age and comorbidity.⁴ Major complications include perforation, post-polypectomy bleeding, and adverse events related to sedation.⁴ Perforation rates, though rare, are a serious concern, with studies indicating an incidence ranging from 0.03% to 0.2% in the general screening population.⁴ However, this rate can be significantly higher in older adults, particularly those over 75, reaching up to 0.5% in some cohorts.⁵ Factors contributing to this increased risk include colonic diverticulosis, thinner colonic walls, and the presence of multiple comorbidities.⁵

Post-polypectomy bleeding is another significant complication, occurring in approximately 0.1% to 0.6% of cases, with a higher incidence observed in patients on antithrombotic therapy or those with larger polyps.⁶ Older age is an independent risk factor for post-polypectomy bleeding, requiring hospitalisation in some instances.⁶ Sedation-related adverse events, including cardiorespiratory depression, are also more common in older patients due to altered pharmacokinetics and pharmacodynamics, and the presence of underlying cardiovascular or pulmonary disease.⁷ These events can lead to hospitalisation, intensive care unit admission, and, in rare cases, mortality.⁷

A critical consideration is the patient's overall health status, often quantified by measures such as the Charlson Comorbidity Index or American Society of Anesthesiologists (ASA) physical status classification.⁸ Frail older adults, or those with multiple severe comorbidities, are at a substantially higher risk of adverse events from colonoscopy and its preparation.⁸ The bowel preparation itself can induce dehydration, electrolyte imbalances, and renal impairment, which are particularly hazardous in vulnerable older patients.⁹

Given these escalating risks, the decision to perform a screening colonoscopy in an average-risk individual over 75 years must be carefully weighed against the potential for benefit. For individuals with a life expectancy of less than 5 to 10 years, the benefits of preventing CRC through screening colonoscopy are likely minimal, while the risks of the procedure remain.³ Alternative screening modalities, such as stool-based tests (e.g., faecal immunochemical test, FIT), may offer a safer, less invasive option for older adults who still wish to undergo some form of CRC screening, though their efficacy in this specific age group for primary screening is still under investigation.¹⁰