Mexican immigrant women residing in the US often have better health outcomes than non-Hispanic white women; including lower rates of low birth weight and infant mortality, lower incidence and mortality rates for cancer and cardiovascular disease, and lower all-cause mortality rates [1–5]. This phenomenon is referred to as the “Hispanic Epidemiologic Paradox” [5–7]. One hypothesis to explain this paradox is “selective migration,” which suggests that immigrant women are a healthier subset of the population of origin and therefore have better than expected birth and other health outcomes because they have been positively selected by the migration process due to physical, mental or other health characteristics [1, 3–5, 8, 9]. Another hypothesis is that cultural traditions and behaviors followed in Mexico protect women for some period of time after they immigrate from risks associated with disadvantaged socioeconomic status once in the US [10–12]. These are thought to be related to cultural values and norms intrinsic to the Hispanic community such as the role of social support networks, interpersonal relationships and the importance of family [13, 14].

Negative health behaviors and impacts on health outcomes are associated with acculturation, particularly among Hispanic women [13, 15, 16]. Acculturation refers to the process of adopting new behaviors and practices when individuals come into contact with another culture. There is much evidence in the epidemiologic literature that the multifactorial, complex relationship between declining health behaviors and the process of acculturation is particularly strong among women [10, 17–20]; as women become more acculturated to a “US lifestyle,” they engage in less healthy behaviors, which adversely impacts their health. Therefore, the importance of examining acculturation is in measuring an indicator for potential cultural influences at work in modifying health risk behaviors.

Acculturation among US Hispanic women has been associated with increased alcohol and cigarette use [15, 17, 20–25]. In the Hispanic Health and Nutrition Examination Survey (HHANES), acculturation was found to be a major predictor of cigarette smoking among US Hispanics, with more acculturated individuals reporting higher levels of smoking. This trend was especially marked among females [2, 20, 23, 26]. In California, the prevalence of smoking and number of cigarettes smoked per day is greater among highly acculturated women than among the less acculturated Hispanics [27]. Between 2001–2003, the average prevalence of current cigarette smoking in the US among non-Hispanic white women was 21.8% versus 9.4% among Mexican-born women living in the US (acculturation level not accounted for) [28]. Similarly, data from 2003 show that 61.6% of non-Hispanic white women reported currently consuming alcohol while only 33.4% of Mexican-born women in the US reported current alcohol consumption [28]. Additionally, a much greater proportion of low-acculturated Mexican–American women reported abstaining from alcohol (87.2%) than their more highly acculturated counterparts (53.4%) [29].

Another topic of concern related to this pattern of increasing acculturation and declining health behaviors is that of high-risk sexual behaviors, such as multiple sexual partners. Multiple partners places women at higher risk for sexually transmitted diseases (STD), including HIV, [30] and more than one sexual partner may be more frequent among higher acculturated Mexican immigrants [21, 31]. In a study of 1062 Hispanic women from a northern California community, nearly 75% of low-acculturated women reported only one sexual partner during their lifetime as compared to 46% of moderately acculturated women and about 20% of highly acculturated women [21].

Given the central role of the population of origin in explaining the Hispanic Epidemiologic Paradox, an ideal study to test the two main hypotheses would compare health outcomes and risk profiles between Mexican-born women currently living in Mexico and Mexican-born women who have migrated to the US. Previous binational studies have addressed specific health issues in Mexican and Mexican–American populations such as obesity and diabetes [32], HIV/AIDS [33], and women’s health [34], but few have attempted to specifically examine the health paradox that seems to accompany migration from Mexico to the US [35].

This binational cross-sectional pilot study sought to explore the hypothesis that Mexican-born women living in Madera, California have similar health behavior profiles with regard to smoking, alcohol use and number of sexual partners as Mexican-born women (who had never lived in the US) currently living in Chavinda, Michoacán. It was also expected that this profile changes with increasing levels of acculturation.

Data were collected in Spanish by in-person interviews in Chavinda and Madera. The questionnaire included demographic characteristics, acculturation, women’s health and reproductive issues, and health behaviors including tobacco and alcohol use. All questions were developed from relevant existing survey instruments [21, 37, 38]. The research was approved by the Institutional Review Board at the University of California, Davis.

Acculturation scores were calculated for Madera participants using a 12-item version of the Acculturation Rating Scale for Mexican Americans-II (ARSMA-II) developed by Cuellar and colleagues [38]. The ARSMA-II instrument provides an overall acculturation score based on measures of language use and preference, ethnic identity, ethnic behaviors and ethnic interaction through the use of two subscales, a Mexican-oriented scale (MOS) and an Anglo-oriented scale (AOS). Responses to items on the MOS and AOS range from “not at all” (response score = 1) to “extremely often or almost always” (response score = 5). The MOS and AOS questions were summed separately and a mean calculated for each orientation subscale. The raw acculturation score was calculated by subtracting the MOS mean from the AOS mean. Criteria for determining levels of acculturation were based on mean and standard deviation scores from the ARSMA-II validation study [21, 38]. The ARSMA-II identified five acculturation levels and their corresponding scores as seen in Table 1. Because there were relatively few women in levels II through V, these levels were collapsed to create a “medium/high acculturation” category. The ARSMA-II is a validated multidimensional instrument used in a variety of studies measuring relationships between acculturation and health [21, 39–44].Table 1

Scores for determining acculturation level of Madera, CA participants using ARSMA-II

The selected outcome variables included smoking, alcohol use and number of sexual partners and were chosen because of their relationship to acculturation and public health importance. Because of small sample sizes and low numbers of positive responses for many categories, we dichotomized outcomes as follows: ever having smoked defined as smoked at least 100 cigarettes during lifetime, ever having consumed alcohol defined as more than 12 alcoholic beverages during lifetime, and number of sexual partners defined as one partner (reference group) or more than one partner. Although levels of smoking and alcohol use assessed were low and may not be directly attributable to adverse health outcomes, they were included in analysis because they illustrated behavioral changes that occur within this population. Having more than one sexual partner however, is associated with increased risk for sexually transmitted infections, especially human papillomavirus (HPV) [45, 46].

Associations between place of residence (Mexico vs. US), acculturation level (low vs. medium/high) and the selected health risk outcomes were first evaluated by bivariate analyses, followed by multiple logistic regression analyses. Bivariate analyses compared the outcomes of interest with place of residence and acculturation level; chi-square and Fisher’s exact tests were used to assess these comparisons across groups. Factors such as age, marital status and education level were assessed for effect modification and confounding. Crude and adjusted odds ratios and 95% confidence intervals were calculated for the main outcomes using multivariate logistic regression models that included age, education level and place of residence or acculturation level. Data analysis was performed using SAS^® software, Version 9.2 of the SAS system for Windows^® (SAS Institute Inc., Cary, NC).

Data were analyzed for 195 study participants; 102 women living in Chavinda, Mexico and 93 women living in Madera, Califorina. The ages of study participants ranged from 18 to 49, with a mean age of 32, which did not differ by study location. Overall, almost 80% of women were married or living with a partner with 74.5% of Mexican residents, 89.6% of low-acculturated US residents and 56.3% of medium/high-acculturated US residents reporting married/living together status (Table 2). The average age at immigration for women in Madera was 19 years (median: 19; 25–75th percentile: 15–24 years) and the average length of time in the US was 13 years (median: 13; 25–75th percentile: 7–16 years). Women living in Mexico were less educated than women living in the US, only 30.4% had achieved greater than primary education (approximate 6th grade equivalent). Among US women, low-acculturated women were less likely to have achieved greater than a primary education than their medium/high-acculturated counterparts (54.6% vs. 93.8%) (Table 2).Table 2

Demographic characteristics of Mexican and US women by place of residence and acculturation level

Among US women, age at immigration and the number of years living in the US were strongly associated with acculturation level. The average age at which low-acculturated women migrated to the US was 21 years (median: 20; 25–75th percentile: 17–25 years) and they had lived in the US an average of 11 years (median: 10; 25–75th percentile: 6–15 years). Medium/high-acculturated women came to the US at about age 10 (median: 8.5; 25–75th percentile: 5.5–12.5 years) and had lived in the US on average for 21 years (median: 20.5; 25–75th percentile: 14.5–27 years). Low-acculturated women living in the US were more likely than their medium/high-acculturated counterparts to be married but less likely to have achieved higher than a primary education (Table 2).

There was no difference in smoking prevalence between Mexican and US residents, but the overall prevalence of smokers was very low in both groups (Table 3). Logistic models adjusted for age and level of education did not show any significant association between place of residence or acculturation level with odds of smoking (Table 4).Table 3

Risk behavior characteristics of Mexican and US women by place of residence and acculturation level

Mexican residents were less likely than US residents to have consumed at least 12 alcoholic beverages in their lifetimes (8.8% vs. 24.7%, P = 0.0027). However, models adjusted for age and education comparing Mexican residents to low-acculturated US residents did not statistically differ with regard to alcohol use (Table 4). In comparisons between low-acculturated and more highly acculturated Mexican-born women residing in the US, those in the medium/high-acculturated group were 3.5 times more likely (CI 1.1–11.5) to have consumed at least 12 alcoholic beverages in their lifetime (Table 4). Education was independently associated with greater odds for alcohol use regardless of place of residence or acculturation level (results not shown).

Women living in Mexico were less likely to report more than one sexual partner in their lifetimes than US residents (3.9% vs. 15.1%, P = 0.0073). Both crude and models adjusted for age and education comparing Mexican residents and low-acculturated US residents were of borderline significance and suggested that Mexican residents were a third less likely (CI 0.1–1.0) to have more than one lifetime sexual partner (Tables 3, 4). Comparisons by acculturation level approached significance with medium/high-acculturated US residents being 3.8 times as likely (CI 1.0–15.0) to have more than one sexual partner in adjusted models (Table 4).

Results showed that women who consumed alcohol were more likely to smoke cigarettes. Effect modification between place of residence (US or Mexico) and alcohol consumption with smoking was not significant. It is likely that persons who drink are more likely to smoke, regardless of place of residence.