Discussion
The key finding of this study is that first-degree relatives younger than the conventional screening age of 50 were less likely than adults aged 50 or older to have had a colonoscopy. Although studies document screening rates among first-degree relatives of inherited CRC syndromes, few studies are available on first-degree relatives of sporadic CRC patients, even though they are the largest higher-risk subgroup in the population. Our study shows the need for increasing screening rates in this subgroup, particularly first-degree relatives younger than 50 because of the recent increase in CRC among American adults in this age group.
The low colonoscopy rate among younger first-degree relatives (40%) observed in our study should be viewed in light of the multifold increase in colonoscopy rates between 2005 and 2010 (69.7%) among adults in the widely publicized screening age group. Studies of first-degree relatives of sporadic CRC patients either focused on first-degree relatives aged 50 or older or used mixed-age samples without distinguishing younger first-degree relatives. Our other study findings are also consistent with those of earlier studies. Among the population aged 50 or older, colonoscopy rates were higher among first-degree relatives than among nonfirst-degree relatives. A recent study using NHIS 2010 data on adults aged 50 or older reported colonoscopy rates of 72.3% among first-degree relatives and 53.5% among nonfirst-degree relatives, similar to our finding. A study based on NHIS 2000 data on adults aged 41 to 75 reported colonoscopy rates of 27.8% among first-degree relatives and 7.7% among nonfirst-degree relatives. Only 1 population-based study using NHIS 2000 data on younger first-degree relatives is available: although it did not distinguish among screening types, it reported that 15.8% of men and 8.9% of women aged 40 to 49 had a CRC screening test. One meta-analysis of 7 studies reported a pooled colonoscopy rate of 40% among all first-degree relatives aged 40 or older; no study in the analysis included recent data.
Our findings are also consistent with the findings of single-center studies. A practice-based patient survey in 2004 showed a colonoscopy rate of 29.6% among first-degree relatives younger than 50 and a rate of 76% among first-degree relatives aged 50 or older. Only 39% of first-degree relatives younger than 50 had ever been asked by their physician about a CRC family history, and almost half (46%) believed that screening should begin at age 50. Another study reported that the lack of physician recommendation was the single most important reason that first-degree relatives younger than 50 years had not undergone colonoscopy screening. Lack of awareness among first-degree relatives of the need for early screening and lack of physician recommendation appear to be major reasons for the low screening rates among first-degree relatives younger than 50. Screening education may have a greater effect among first-degree relatives because of their personal exposure to CRC through family members.
Consistent with prior studies, we found that having health insurance increased the likelihood of colonoscopy screening. Colonoscopy screening rates among Medicare enrollees increased after 2001, when colonoscopy coverage was launched, from a mean quarterly rate of 285 per 100,000 beneficiaries during 1992–1997 to 1,919 per 100,000 beneficiaries during 2001–2002. The Affordable Care Act (ACA) now requires first-dollar coverage of preventive services, including colonoscopy, a provision that was not in force during the NHIS 2010 survey. Screening promotion among younger first-degree relatives in the ACA environment has a better chance of increasing screening rates than in the pre-ACA environment, although we would expect some attenuation of effect because of the general tendency of younger adults not to avail themselves of preventive health services and because grandfathered health plans are not required to conform to ACA provisions.
Our study has several limitations. One is response-rate bias: half of the sample did not answer the family history question, and they were systematically different from the half that did answer the question: they were half as likely as nonfirst-degree relatives to have undergone colonoscopy screening. Another limitation is that data were self-reported (ie, data were not extracted from medical records), which may have resulted in overestimation of screening rates. Finally, imbalanced cell sizes of the family history variable (2,470 vs 10,454) may limit the accuracy of odds ratio estimates.
Despite these limitations, our study is important in highlighting that first-degree relatives aged 40 to 49 of CRC patients are an undertargeted (and potentially rewarding) group for focused promotion of CRC prevention. Screening promotion should target both physicians and patients: alerting primary care physicians to engage younger patients in learning about a potential CRC family history and educating CRC patients to alert their first-degree relatives to initiate screening discussions with their physicians. Our recent report of an 83% reduction in CRC incidence and an 89% reduction in CRC mortality after screening colonoscopies should boost enthusiasm for colonoscopy screening among both patients and physicians. Coupled with the ACA provisions requiring coverage of screening procedures, such efforts can help arrest the increase in CRC among Americans younger than 50 years.