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Showing content from https://pmc.ncbi.nlm.nih.gov/articles/PMC1448533/ below:

Underuse of Screening Sigmoidoscopy and Colonoscopy in a Large Cohort of US Adults

Objectives. We examined the prevalence of endoscopy (sigmoidoscopy or colonoscopy) by indication and by demographic and lifestyle factors.

Methods. We analyzed cross-sectional data collected in 1997 from participants aged 50 years and older in the Cancer Prevention Study (CPS) II Nutrition Cohort.

Results. Fifty-eight percent of men and 51% of women reported ever having undergone endoscopy; only 42% of men and 31% of women reported endoscopy for screening rather than for disease diagnosis or follow-up. Prevalence varied by demographic and lifestyle factors.

Conclusions. Efforts to increase colorectal cancer screening need to target women, all persons aged 50–64 years, and those with colorectal cancer risk factors. Future studies should distinguish endoscopy for screening from procedures for disease diagnosis and follow-up to avoid overestimating screening compliance.

Flexible sigmoidoscopy1–4 and colonoscopy5–9 have been shown to be effective in reducing colorectal cancer mortality by allowing for the early detection and removal of colorectal cancers and preneoplastic lesions. Despite the known efficacy of colorectal cancer screening and widely publicized screening guidelines issued by national organizations since the late 1970s,10–16 the use of endoscopic screening in the general population remains low.17–22 According to the 1998 National Health Interview Survey (NHIS), only 37% of adults aged 50 and older reported having ever undergone sigmoidoscopy.21 The 2001 Behavioral Risk Factor Surveillance System (BRFSS) found that 47% of adults aged 50 years and older reported ever receiving lower endoscopy;22 this national survey17,22 does not separate procedures for colorectal cancer screening from tests for disease diagnosis or follow-up. Population-based prevalence estimates of endoscopy use also do not distinguish procedures performed in high-risk persons from those performed in average-risk persons, even though screening guidelines now specify earlier and more frequent screening in persons at high risk, based on personal and family history of colorectal diseases.13–16 Furthermore, little is known about demographic and lifestyle factors associated with screening endoscopy beyond health insurance coverage and access to health care.19,20,23

One of the Healthy People 2010 objectives is to increase to 50% the proportion of adults aged 50 years and older who have ever undergone a sigmoidoscopy.21 The corresponding American Cancer Society 2015 objective is to increase the usage of endoscopic screening, fecal occult blood testing (FOBT), or both to 75% in adults aged 50 years and older.24 We analyzed cross-sectional data collected in 1997 from participants in the Cancer Prevention Study (CPS) II Nutrition Cohort to examine the prevalence of endoscopy use for colorectal cancer screening (as distinguished from disease diagnosis and surveillance) and to identify demographic and lifestyle factors associated with use of screening endoscopy.

The CPS II Nutrition Cohort25 was established in 1992–1993; it consists of 86 404 men and 97 786 women recruited from among members of the CPS II Baseline Cohort (enrolled in 1982 by American Cancer Society volunteers in all 50 states, the District of Columbia, and Puerto Rico). CPS II Nutrition Cohort participants included men and women aged 50–74 years residing in 1 of 21 states with population-based cancer registries. The median age at cohort entry in 1992–1993 was 63 years. Cohort participants were enrolled by completing and returning a mailed, self-administered questionnaire; cohort recruitment details have been described elsewhere.25 The CPS II Nutrition Cohort was recontacted with self-administered questionnaires in 1997, 1999, 2001, and 2003. In the current study, we analyzed cross-sectional data from the 1997 questionnaire. In general, CPS II Nutrition Cohort participants report higher educational attainment and more health-conscious behaviors than the general US population.25

Excluded from this analysis were CPS II Nutrition Cohort members who did not return a completed 1997 questionnaire (11% of men and 10% of women); those who provided uninterpretable responses to questions on sigmoidoscopy or colonoscopy (7% of men and 6% of women); and persons with missing information (2% of men, 2% of women) on race, education, health care coverage, visiting a doctor’s office or clinic in the past 2 years, or use of other cancer screening tests [prostate-specific antigen (PSA) test for men and mammogram or Papanicolaou (Pap) test for women]. Also excluded from our study were 4 men and 187 women aged younger than 50 years included in the CPS II Nutrition Cohort because they were married to a cohort participant aged 50 years and older. After all exclusions (20% men and 19% women), our analysis was based on 58 204 men and 71 042 women who represented 81% of the CPS II Nutrition Cohort.

History of sigmoidoscopy or colonoscopy (referred to here as endoscopy or endoscopic procedures) was ascertained from the question “Have you ever had a sigmoidoscopy or colonoscopy of the bowel?” Respondents who marked “yes” to this question were asked about the number of procedures and year and reason for the most recent procedure. Procedures were categorized into 3 groups: (a) diagnostic follow-up because of a positive FOBT or symptoms of pain, diarrhea, or visible blood in stool; (b) diagnostic follow-up because of previous colorectal cancer; or (c) colorectal cancer screening. The third category of screening endoscopy was further subdivided into endoscopy to follow up on a personal history of colorectal polyp; a family history of colorectal cancer; or screening in the absence of symptoms, personal history of colorectal polyp, or family history of colorectal cancer.

We examined the prevalence of endoscopy use (ever and within the past 5 years) by indication separately in men and women to examine gender differences (Table 1 ▶). The US 2000 standard population aged 50 years and older was used for age adjustment. Unconditional logistic regression modeling was used to estimate age-adjusted and multivariate-adjusted prevalence odds ratios (PORs) and 95% confidence intervals (CIs) for screening endoscopy, compared with never having had endoscopy, by demographic and lifestyle factors. Multivariate models included all covariates in Table 2 ▶. We further examined endoscopy use stratified by reported health insurance coverage and receipt of another cancer screening test (PSA for men and mammogram or Pap test for women) within the past year. We used the likelihood ratio test based on models with and without interaction terms to test the statistical interaction between gender and covariates. We used the SAS statistical software package for all analyses (SAS Institute Inc, Cary, NC).

Age-Adjusted^aPrevalence of Sigmoidoscopy or Colonoscopy Use, by Reason for the Most Recent Procedure: CPS II Nutrition Cohort Men and Women, 1997

Demographic and Lifestyle Factors Associated With Having Ever Undergone Screening Sigmoidoscopy or Colonoscopy: CPS II Nutrition Cohort Men and Women, 1997

Fifty-eight percent of men and 51% of women (54% of total) in the CPS II Nutrition Cohort reported ever having undergone sigmoidoscopy or colonoscopy, and 40% of men and 32% of women (35% of total) reported endoscopy within the past 5 years (Table 1 ▶). When examined by indication, 15% of men and 19% of women reported endoscopy for diagnostic follow-up of positive FOBT or symptoms, and 2% of men and 1% of women reported follow-up endoscopy for previous colorectal cancer. The prevalence of diagnostic endoscopy and testing because of a family history of colorectal cancer was somewhat higher in women than men, but women had a lower prevalence of screening endoscopy in the absence of symptoms, personal history of colorectal polyp, or family history of colorectal cancer. Approximately 75% of diagnostic procedures reported by men were performed to further evaluate symptoms such as pain, diarrhea, or visible blood in stool, and 25% of diagnostic procedures were performed to follow up on a positive FOBT in the absence of symptoms. Among women, 87% of diagnostic procedures reported were performed to follow up on symptoms and only 13% of diagnostic procedures were performed because of a positive FOBT in the absence of symptoms.

The prevalence of screening endoscopy was substantially lower than the prevalence of total endoscopy (Table 1 ▶), even when procedures for screening in the absence of symptoms, personal history of colorectal polyp, or family history of colorectal cancer were combined with procedures to follow up on a previous colorectal polyp or family history of colorectal cancer. Twenty-nine percent of men and 21% of women (24% of total) reported a screening endoscopy within the past 5 years; slightly more than half of these procedures were performed for screening without symptoms, personal history of colorectal polyp, or family history of colorectal cancer.

The majority of men (69%) and women (87%) in this cohort reported having current health insurance coverage and having received at least 1 other cancer screening test in the past year. In this subgroup, 66% of men and 54% of women reported having ever received any endoscopy (Table 1 ▶). Although the prevalence of having ever undergone a screening endoscopy and of testing within the past 5 years was the highest in this subgroup, only 35% of men and 23% of women reported a screening endoscopy within the past 5 years.

Among persons who reported no health insurance coverage or no other cancer screening test in the past year, 31% of men and 16% of women reported any screening endoscopy, and 19% of men and 8% of women reported screening endoscopy within the past 5 years (Table 1 ▶).

Table 2 ▶ shows the estimated age-adjusted and multivariate-adjusted POR (95% CI) for reporting ever receipt of a screening endoscopy in relation to demographic and lifestyle factors in men and women separately. Adjusting for multiple covariates, screening endoscopy was negatively associated with being aged younger than 65 years (especially aged younger than 60 years); reporting full-time work or disability compared with retirement; lack of health insurance; not having had another cancer screening test in the past year; and being overweight or obese, physically inactive, or currently smoking cigarettes. Persons aged 75 years and older were less likely to have had a screening endoscopy than those between the ages of 65 and 74 years.

Factors positively associated with screening endoscopy included the following: education beyond high school, having visited a doctor in the past 2 years, private health insurance coverage, a personal history of colorectal polyp, a personal history of cancer other than colorectal cancer or a non-cancer health condition, a family history of colorectal cancer, current use of supplemental vitamins or fiber laxatives, having quit smoking cigarettes (women), and moderate daily alcohol consumption. These associations did not change substantively when procedures for follow-up of colorectal polyp were excluded from screening procedures (data not shown).

Women were significantly less likely than men to report ever undergoing a screening endoscopy; the POR (95% CI) for screening endoscopy was 0.56 (0.54–0.59) for women compared with men, adjusting for all covariates in Table 2 ▶. Within the following demographic subgroups, women were especially less likely than men to report a screening endoscopy: the POR (95% CI) was 0.42 (0.37–0.47) among those aged 50–59 years and 0.50 (0.47–0.53) among those aged 60–64 years (P value for interaction<.0001), 0.52 (0.50–0.54) among those reporting any education beyond high school (P value for interaction < .0001), and 0.49 (0.45–0.53) among those who reported no other cancer screening test in the past year (P value for interaction = .0007).

Demographic and lifestyle factors associated with screening endoscopy were in general similar in persons with and without health insurance coverage and those having had another cancer screening test recently (data not shown). One exception was that a personal history of cancer or non-cancer health conditions was strongly associated with screening endoscopy among persons reporting no health insurance coverage or other cancer screening, whereas no such association was observed among those reporting health insurance coverage and recent screening for other cancer.

Even in the CPS II Nutrition Cohort, a health-conscious population in the United States, reported usage of sigmoidoscopy and colonoscopy in the 5 years before 1997 was low (35%), albeit higher than that reported in the general US population during the same year (30%).26 Based on our finding that nearly one third of the endoscopic procedures reported in this study were for disease diagnosis or follow-up rather than for colorectal cancer screening, the prevalence of screening endoscopy is likely overestimated in national surveys that do not distinguish screening from other indications.

In the general population, self-reported use of endoscopy for any reason continues to be low, even in more recent years.17,18,22,27 The 2001 BRFSS survey22 found that 39% of respondents aged 50 years and older reported undergoing sigmoidoscopy or colonoscopy within the past 5 years for any reason; the BRFSS surveys do not distinguish screening from diagnostic procedures. The NHIS18,27 ascertained the reason for the most recent procedure and reported that, in 1998, 27% of respondents had undergone proctoscopy within the past 5 years for any reason. Only 16% of NHIS27 respondents reported proctoscopy for screening in the past 5 years (compared with 24% in the CPS II Nutrition Cohort using the same standard population for age adjustment). Although the NHIS estimates do not include use of colonoscopy, the higher estimates of screening endoscopy in our study are more likely attributable to the higher levels of education and health insurance coverage in this study population.

As in previous studies,19,20,23,27 we found indicators of access to health and preventive care, such as education and health insurance coverage, to be important predictors of endoscopy usage. Even among CPS II Nutrition Cohort members who reported having current health insurance coverage and having had another cancer screening test within the past year, only approximately one third of men and fewer than one fourth of women reported receiving a screening endoscopy within the past 5 years. However, the self-reported data on insurance coverage in our study did not specify whether the coverage included screening endoscopy.

It is paradoxical that although women are generally more likely than men to report use of preventive care, including the FOBT,19,20,28 women consistently reported lower prevalence of any endoscopy use than men in our study and in national surveys.18,19 Women in the CPS II Nutrition Cohort were significantly less likely than men to report endoscopy for screening, especially among those (a) who were aged younger than 64 years, (b) who reported higher educational attainment, and (c) who reported no other cancer screening test in the past year. However, even among women who reported a mammogram or Pap test within the past year, only one third reported ever undergoing screening endoscopy. Although the prevalence of diagnostic endoscopy was higher in women than in men, most (87%) of these were performed because of presence of symptoms rather than to resolve a positive FOBT in the absence of symptoms. Because many women receive medical and preventive care from their obstetrician/gynecologist only, it has been suggested that clinicians in these disciplines could play a crucial role in colorectal cancer prevention in women by recommending colorectal cancer screening and by ensuring appropriate follow-up of positive FOBT.29

Consistent with findings from population-based studies,18,19,27,30 our study found that persons between the ages of 50 and 64 years were significantly less likely to have had a screening endoscopy than those between the ages of 65 and 74 years, regardless of health insurance coverage and receipt of other cancer screening tests. The lower likelihood of screening endoscopy may relate to lower perceived risk of colorectal cancer or lack of health insurance coverage for screening endoscopy in those who are asymptomatic. A review of coverage mandates for cancer screening by US private insurers found that 43 states and the District of Columbia mandated coverage of prostate, breast, and cervical cancer screening in 1998, yet only 1 state mandated coverage of colorectal cancer screening.31 Men and women between the ages of 50 and 64 years represent an important group for targeting colorectal cancer screening efforts to prevent colorectal cancer in older adults.

We observed significantly lower likelihood of screening endoscopy among persons who reported being overweight or obese, physically inactive, or current cigarette smokers, factors associated with increased risk of colorectal cancer in many studies.32 Overweight or obese women are also reportedly less likely to be screened for cervical and breast cancer,33 perhaps because of physicians not recommending screening or less compliance of overweight or obese women with screening recommendations.

Our results show that the likelihood of screening endoscopy increases significantly with the self-reported number of first-degree relatives with colorectal cancer. In addition to physicians being more likely to recommend endoscopy to persons with a family history of colorectal cancer, it is possible that persons who are knowledgeable about family cancer history are better reporters of endoscopy use, more likely to request endoscopy, or more likely to comply with physician referrals.

Limitations of our study include the lack of data on FOBT, an important component of colorectal cancer screening guidelines, and the inability to separate the use of sigmoidoscopy from colonoscopy. We assume that screening endoscopies performed in average-risk persons before 1997 were predominantly sigmoidoscopies and that colonoscopies were most likely performed in persons considered to be at increased risk because of family history of colorectal cancer or personal history of colorectal polyp. Similar to the national surveys,22,27 our data on sigmoidoscopy and colonoscopy were self-reported and not validated. Validation studies34–36 have shown that the use of these procedures can be recalled with reasonable accuracy but may overestimate the occurrence of procedures and underestimate the time since the last procedure. One study34 reported better than 70% agreement between self-report and medical record audit (considered gold standard) data on the reason for sigmoidoscopy and cautioned that screening history may not always be better captured in medical records than patients’ self-report.

The main strengths of this study are the ability to distinguish colorectal cancer screening procedures from those for disease diagnosis and follow-up and the ability to examine screening endoscopy in relation to a range of demographic and lifestyle factors. Although the CPS II Nutrition Cohort is a select cohort, its sample size is substantially larger than the NHIS and BRFSS samples, which allows us to obtain stable estimates by covariates. We showed that the prevalence of screening endoscopy was particularly low in women and all persons between the ages of 50 and 64 years and that the colorectal cancer risk factors of being overweight or obese, physically inactive, and a current cigarette smoker were associated with significantly lower likelihood of screening endoscopy.

Although the prevalence of having ever received a sigmoidoscopy or colonoscopy in this cohort of adults meets the objective of Healthy People 2010,21 only approximately two thirds of the reported procedures were for screening and not for disease diagnosis or follow-up. National surveys that do not differentiate endoscopy use by indication overestimate the prevalence of endoscopy for screening. Studies of compliance to current screening guidelines also may need to separate persons at average risk of colorectal cancer from those at high risk because of family or personal history of colorectal disease. We concluded that efforts to increase colorectal cancer screening need to target women, all persons aged 50–64 years, and those with colorectal cancer risk factors and that future national surveys should distinguish endoscopy for screening from procedures for disease diagnosis and follow-up.

Cancer Prevention Study II Nutrition Cohort is funded by the American Cancer Society. Ann Chao is supported by the American Cancer Society and the National Cancer Institute (grant K07CA75062).

Human Participant Protection…The study protocol was approved by the Emory University institutional review board.

Contributors…A. Chao designed the study and drafted the article. C. J. Connell conducted the data analysis. V. Cokkinides, E. J. Jacobs, E. E. Calle, and M. J. Thun contributed substantially to conceptualizing ideas, interpreting the data, and revising the article.

Peer Reviewed

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