INTRODUCTION

Colorectal cancer is the second leading cause of cancer-related death in the US1. Colorectal cancer (CRC) screening has been shown to effectively reduce mortality and morbidity from colorectal cancer due to early detection and treatment of cancer or precancerous lesions and is recommended for all average risk adults aged 50 and over2. Modest improvements in the utilization of CRC screening procedures have occurred in the past few years in the context of expanding Medicare coverage3. However, wide health disparities remain among Latino and non-Latino Whites, Asians and non-Latino Whites, and immigrants and their native counterparts4–8.

Immigrants’ poorer cancer screening practices relative to US natives may be related in part to immigrants having different values and beliefs about health service use9–11 or low levels of acculturation to US social norms concerning cancer screening. Several studies among Latino and Asian ethnic minority groups examine acculturation’s influence on colorectal cancer screening with mixed findings. Two studies on acculturation and CRC screening among Latinos found no association between acculturation and CRC screening after accounting for socio-economic factors and access to care12,13. In contrast, the majority of studies conducted in various Asian ethnic groups found that greater acculturation was associated with a higher likelihood of CRC screening14–19. Interpreting results of these studies is challenging due to varying study methodologies. Each study used a different measure of acculturation. Some used variants of English language preference or proficiency12,16,17, or time in the US measures18,19, while others used composite measures of acculturation13–15 reflecting concepts of language preference, time and co-ethnic relationships. Two studies measured ever using any CRC screening method13,15, while the remaining studies measured CRC screening based on recommended guidelines [i.e., fecal occult blood test (FOBT) in the past year or endoscopy in the past 5 years]12,14,16–19. The majority of the studies relied on convenience samples of adults, with notable exceptions12,17,19.

Most importantly, among the studies focusing on Latinos, none stratified analyses by country of origin. Past research has shown differential relationships between acculturation and health by ethnic group20,21; thus, aggregate analyses may underestimate the influence of acculturation, mask important ethnic group-specific patterns or produce contradictory findings. For breast cancer screening, national studies lumping Latino groups together and those that have had a more regional focus have produced inconsistent results with regard to the associations between acculturation and breast cancer screening, possibly because of varying ethnic group distributions22–27. Further, each ethnic group experiences a unique acculturation experience shaped by US immigration policy and the social and economic conditions of the receiving community at the time of immigration28,29.

Study Objectives

The primary goal of this study is to investigate the relationship between acculturation and colorectal cancer (CRC) screening in Latino adults 50 and older using nationally representative data. We address two important gaps in the literature. First, we stratify our analyses by national origin, examining whether the relationships between acculturation and CRC screening vary among groups of Mexican, Puerto-Rican and Cuban origin; no single existing study has done such a comparative analysis. Second, no past nationally representative study on acculturation and CRC screening has examined the different CRC screening modalities separately, an important consideration given the variability in access to, cost and nature of the different modalities. We examine the relationship between acculturation and three different CRC screening outcomes separately—FOBT, endoscopy and any CRC screening modality—all according to recommended guidelines. Acculturation has been conceptualized as a multidimensional process whereby immigrants adopt selected values and behaviors of their host culture and may discard or retain those of their country of origin28,30–32. We relate acculturation to CRC screening taking into consideration factors central to the behavioral model of health-care utilization, which suggests that health service utilization is a function of individuals’ predisposition due to age, gender or social status, factors that enable or impede use of services (such as health insurance), and actual need for health care33.

METHODS

This study used data from the 2000, 2003 and 2005 National Health Interview Survey (NHIS), the principal source of information on the health of the civilian non-institutionalized population of the US. The NHIS is an ongoing, nationally representative, household, in-person survey conducted by the National Center for Health Statistics, Centers for Disease Control and Prevention (http://www.cdc.gov/nchs/nhis). To facilitate stratification by ethnic group, we combined the three survey years (NHIS 2000, 2003 and 2005) containing detailed data on colorectal cancer screening procedures. For the purpose of this study, we analyzed all adults 50 years of age and older without a prior history of colon or rectal cancer and who self-reported being Hispanic/Latino. A current feature of the NHIS sampling design is the oversampling of Latinos, permitting analyses of Mexicans, who constitute the single largest Latino ethnic group in the US, followed by Puerto Ricans and Cubans34. Thus, analyses were conducted separately for Mexican (N = 2,304), Puerto-Rican (N = 503) and Cuban (n = 484) adults to examine subgroup-specific relationships between acculturation and CRC screening.

Dependent Variables

Three CRC screening outcomes, available in the NHIS, were investigated: (1) whether individuals had undergone FOBT in the past year, (2) whether individuals had received a sigmoidoscopy in the last 5 years or colonoscopy in the last 10 years and (3) whether individuals had received any up-to-date CRC screening (or met the criterion for no. 1 or 2). These CRC screening criteria were based on clinical guidelines that were in place prior to the study period35.

Independent Variables

Acculturation was operationalized with two discrete variables: (1) nativity—whether the respondent was born outside the 50 US states or not (hereafter referred to as mainland US and (2) language preference—whether the respondent conducted the interview in English or not. Language has been shown to be a powerful indicator of ethnic identity, and nativity has been identified as a key objective measure of acculturation36–40. Nativity reflects exposure to US culture, and studies have shown that longer exposure to competing values of the larger society are expected to diminish the influence of values unique to an ethnic culture36.

We also analyze key covariates, including demographic variables (age, sex) and socio-economic factors known as predisposing variables (income status, education), enabling factors or those related to health-care access (type of insurance and usual source of care) and health-care need factors (number of chronic diseases), which is a count variable ranging from 0 to 6, of whether the respondent reported having diabetes, hypertension, ulcer, arthritis, any cardiovascular disease and any respiratory illness.

Statistical Analyses

We examined bivariate and adjusted relationships between acculturation measures and all three CRC screening outcomes. We used chi-square tests to examine unadjusted associations between nativity and language of interview and the three outcomes. Using logistic regression, models containing nativity, language of interview and all covariates were estimated to assess the independent contributions of each on the three outcomes. All analyses were adjusted for complex survey design using SAS (version 9.1.3) and SUDAAN41.

RESULTS

Sample Characteristics

Table 1 presents characteristics of adults who met the study inclusion criteria (non-Hispanic Black and White adults are presented for comparative purposes). Overall, the majority of Mexicans and Puerto Ricans conducted the interview in English (approximately 60%), while the majority of Cubans conducted the interview in Spanish or a combination of Spanish and English (75%). The majority of Mexicans were born in the US (56%). In contrast, the majority of Puerto Ricans and Cubans were born outside the mainland US, (79% and 95% respectively). Socioeconomic and health-care factors varied by national origin and racial and ethnic groups. For example, the percentages of college graduates ranged from 7% and 8%, respectively, among Mexican and Puerto-Rican adults to 20% among Cubans. Finally, the percentage of uninsured ranged from 9% among Puerto-Rican adults to 23% among Mexican adults.

Table 1 Respondent Characteristics (%) by Racial and Ethnic Group*, NHIS† 2000, 2003, 2005
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Rates of CRC Screening According to Nativity and Language of Interview

The rate of any up-to-date screening ranged from 29% among Mexicans to 37% among Cubans, and the rate of up-to-date endoscopy ranged from 24% among Mexicans and 31% among Cubans (Table 2). There was less variation in FOBT in the past year according to ethnic group (Table 2).

Table 2 CRC Screening Outcomes by Nativity and Language of Interview*: NHIS 2000, 2003, 2005†
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Table 3 Adjusted Odds Ratios (95% CI) for Any Up-To-Date Colorectal Cancer Screening*: NHIS 2000, 2003, 2005†
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There was wide variation by nativity and language of interview for all three CRC screening outcomes across ethnic groups. Among Mexicans, US-born adults and those who had English language interviews had significantly higher rates of all CRC screening outcomes measured compared to those born outside the US and who did not interview in English. In contrast, among Puerto-Rican and Cuban adults, rates for all CRC screening outcomes were higher in foreign-born adults relative to their US-born counterparts (with the exception of endoscopy among Puerto Ricans where the rates were similar). Further, compared to Cubans who had a Spanish/bilingual interview, those who had an English language interview had lower rates of all CRC screening outcomes; this was also true for FOBT use among Puerto Ricans.

Adjusted Analyses for Any Up-to-date Screening, FOBT in the Past Year, Up-to-date Endoscopy

After adjusting for all covariates in the model, including demographic variables (age, sex), predisposing (income, education), enabling (insurance and usual source of care) and need (number of chronic conditions) factors central to the health service utilization model, there are significant independent associations between nativity and any up-to-date CRC screening (Table 3). For example, Mexicans who were born in the US had higher odds of reporting any up-to-date screening compared to those born outside the US (OR = 1.4; 95% CI: 1.0-1.9). It is also notable that for Mexicans, family poverty level, education, usual source of care and number of chronic conditions all had independent associations with CRC screening.

In contrast, nativity and language of interview were not significant correlates of any up-to-date CRC screening among Puerto Ricans and Cubans (Table 3). Higher family income and a greater number of chronic conditions were significantly associated with a higher likelihood of any up-to-date CRC screening among Cubans. Insurance coverage, higher educational levels, male gender, and greater number of chronic conditions were also positively related to any up-to-date screening among Puerto Ricans only.

Interestingly, for FOBT, the study’s acculturation measures were only significant among Puerto Ricans (Table 4). Puerto Ricans who were born in the mainland US were less likely to report receiving an FOBT in the past year compared to those born outside the US. In contrast, Puerto Ricans who interviewed in English were more likely to report FOBT in the past year than those who interviewed in Spanish. It is notable that higher educational level and a greater number of chronic conditions were also significant and positively related to having received an FOBT in the past year among Puerto Ricans. Among Mexicans, having a usual source of care and a greater number of chronic conditions were significant and positive correlates of FOBT in the past year. Among Cubans, male gender was the only significant, positive correlate of the outcome.

Table 4 Adjusted Odds Ratios (95% CI) for Receipt of FOBT *in Past Year†: NHIS 2000, 2003, 2005‡
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Nativity mattered in the receipt of up-to-date endoscopy only for Mexicans (Table 5). For Mexicans, those who were born in the US were more likely to report an up-to-date endoscopy than those born outside (1.5; CI: 1.1-2.2). Additionally, higher family incomes, higher educational levels, having a usual source of care and a greater number of chronic conditions were significant, positive correlates of up-to-date endoscopy among Mexicans. Higher family incomes, higher educational levels, male gender and a greater number of chronic conditions were significant, positive correlates among Puerto Ricans; higher family incomes, age and a greater number of chronic conditions were significant positive correlates among Cubans.

Table 5 Adjusted Odds Ratios (95% CI) for Up-To-Date Endoscopy*†: NHIS 2000, 2003, 2005 ‡
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DISCUSSION

This study demonstrates that acculturation, inferred by nativity and language preference, is a significant determinant of CRC screening utilization in a nationally representative sample of older Latino adults even when taking into account a variety of health service utilization factors. For Mexican adults, US nativity was positively associated with any up-to-date screening or an up-to-date endoscopic procedure. The findings among Puerto Ricans were more complex with evidence of both positive and negative associations with the acculturation measures used in this study. Puerto Ricans who had an English language interview were more likely to receive FOBT in the past year relative to those who had a Spanish/bilingual interview; in contrast, Puerto Ricans who were born in the mainland US were less likely to receive FOBT in the past year relative to those born in Puerto Rico. There were no significant associations between acculturation and CRC screening among Cubans in adjusted analyses.

Enabling factors (insurance type and usual source of care) were also significant determinants of CRC screening for almost all ethnic groups and all CRC screening modalities. Further, for the more expensive screening modalities (e.g., colonoscopy or sigmoidoscopy), the conventional predisposing factors (income status and educational level, which can also be conceptualized as enabling factors) remained robust determinants. For FOBT, the less expensive test, however, predisposing factors were not significant determinants. The only exception to these findings was FOBT utilization among Puerto Ricans where, in addition to the acculturation measures and chronic conditions, educational level was a significant determinant.

These results are in contrast to those in an earlier study among Latinos that found an insignificant association between acculturation and CRC screening13. However, Shah et al. (2006) analyzed up-to-date screening among Latinos as an aggregate group, while our study disaggregated analyses by Latino national origin and CRC testing modality. Thus, aggregating ethnic groups and grouping CRC testing modalities together may lead to missed opportunities in identifying important predictors of CRC screening.

Our findings highlight the diversity of Latinos in the US by suggesting differential relationships between acculturation and CRC screening by national origin. Among Mexicans in our study, we observed a positive relationship: US nativity was associated with a higher likelihood of endoscopy and overall up-to-date CRC screening. Among Puerto Ricans, we observed the opposite relationship: US nativity was associated with a lower likelihood of FOBT use. These findings are consistent with evidence of differential associations by ethnic group between acculturation and preventive behaviors20. Allen et al. (2007) find overall improvement of preventive behaviors among Asian teens from one generation to the next and steady or worsening preventive behaviors among Latino teens20. These differential associations are also supported by contemporary theories of assimilation, which characterize heterogeneous paths of social mobility from one generation to the next28, leading to better or worse preventive behaviors.

The findings among Mexicans suggest US natives, relative to their Mexican origin counterparts, may be more likely to possess certain social norms or skills that encourage or facilitate cancer screening utilization. For example, because of their greater exposure to the US culture and medical system, US-born Mexicans may be more comfortable at discussing their health concerns with providers, be more skilled at navigating the health-care system or have more exposure to social circles that support positive screening behaviors when compared to their Mexican origin counterparts11,17,24,42–44. Older Mexican adults born in Mexico, relative to those born in the US, may also be more likely to mistrust the medical system, an interpretation consistent with a study of acculturation and breast cancer screening, which found that less acculturated Latina women were more likely to be suspicious of their medical care and screened less frequently45.

In contrast to the older Mexican adults in our study, mainland US nativity has a negative association with FOBT use among Puerto Ricans. This finding is consistent with recent work comparing willingness to participate in cancer screening among San Juan and New York City (NYC) Puerto Ricans, which found higher rates among San Juan Puerto Ricans46. Claudio et al.46 explain that San Juan Puerto Ricans, relative to NYC Puerto Ricans, possibly have greater exposure to health information and services because of the strong presence of the pharmaceutical and health-care industry in Puerto Rico, which is also a possibility in this study. Further, consistent with studies finding a positive association between provider patient language concordance and health care, Puerto-Rican health-care providers, compared to US health-care providers, may have been more effective at promoting FOBT use among their Puerto-Rican patients because of their shared culture and language47–49.

Finally, an important finding of this study is the divergent relationships between nativity and language of interview and FOBT use among Puerto Ricans. Because Puerto Rico is a US territory, mainland US nativity and English language preference may reflect different constructs than they do in other ethnic groups. While mainland US nativity may reflect exposure to imperfect social and health-care systems, English preference may reflect a process of acculturation that leads to a weakening of attitudes that foster feelings of fear, embarrassment or invulnerability discussed in previous studies of Latinos and Puerto Ricans in particular50,51, and adoption of more positive beliefs about cancer screening.

We should note some important limitations. First, estimated rates of CRC screening were based on self-report. However, a prior study found good agreement between self-report data and medical records for sigmoidoscopy and colonoscopy52. Second, we were not able to discern whether colonoscopies were performed for diagnostic or screening purposes, potentially overestimating CRC screening rates. Third, we were unable to examine physician recommendations for the test because NHIS does not collect these data. Physician recommendation data were collected in the 2000 and 2005 NHIS, but only for respondents who were never screened or who did not screen within the recommended timeframe.

US nativity and interview language were the only acculturation proxies available in all 3 years of NHIS. Although alone these measures may not capture the complexity of the acculturation process, US nativity offers an approximation of exposure to the dominant culture, while language measures have been shown to explain most of the variance in acculturation scales53. Further, both measures constitute a systematic approach to measuring acculturation12–19,31,39.

CONCLUSION

The results underscore the importance of targeting less acculturated individuals to promote CRC screening utilization in ethnically diverse settings. Clinicians, however, need to recognize the complexity of acculturation and treat common indicators, such as nativity and language as independent dimensions among their Latino patients.