Abstract
Objectives. To investigate the association between acculturation and diabetes risk in the Mexican American Mano a Mano (hand to hand) Cohort.
Methods. We recruited 15 975 men and women in the Houston, Texas, area from 2001 to 2014. We used language use, birth country, and duration of US residence (among Mexico-born) to assess acculturation. Participants self-reported a physician’s diagnosis of diabetes during annual follow-up over an average of 5.4 (range = 1–13) years. Self-reported diabetes status was validated in medical records for a subset of 235 participants with 98% agreement.
Results. Diabetes risk was higher among immigrants with 15 to 19, 20 to 24, and 25 or more years (relative risk = 1.47; 95% confidence interval = 1.07, 2.01) of US residence, relative to those with less than 5 years. Neither language acculturation nor birth country was significantly associated with diabetes risk.
Conclusions. Among participants born in Mexico, diabetes risk increased with longer duration of US residence.
In the United States, diabetes prevalence among Mexican American persons is nearly twice that of non-Hispanic White persons (13.9% vs 7.6%).1 To improve diabetes prevention and screening efforts, it is critical to understand the basis for the disproportionate diabetes burden in this population.
Genetic predisposition has been proposed as one reason for the disparity. However, comparisons of genetically similar Mexican and Mexican American populations have shown the importance of environmental and lifestyle factors, with higher diabetes prevalence among the latter group.2 This suggests that assimilation into US culture may contribute to the diabetes burden. Acculturation, or the adoption of the attitudes, values, customs, beliefs, and behaviors of the host culture,3 has been associated with some unhealthy behaviors4 and poor health conditions5 among Hispanic people. Importantly for diabetes risk, greater acculturation has been associated with increases in body mass index (BMI; defined as weight in kilograms divided by height in meters squared)4 and adoption of poor dietary habits6 among Hispanic individuals.
Previous studies have investigated acculturation and diabetes outcomes among Hispanic persons with inconsistent results. However, few have used prospective data from a large population-based cohort of Hispanic persons. The purpose of this study was to examine diabetes risk in relation to acculturation among Mexican American persons.
METHODS
Data for these analyses came from the Mexican American Mano a Mano (hand to hand) Cohort, a population-based cohort of Mexican American persons in the Houston, Texas, area. Details of eligibility and recruitment can be found elsewhere.7 Following enrollment, participants completed an interview, during which self-reported diabetes status, acculturation-related variables, and demographic information were ascertained. During annual follow-up interviews, participants self-reported a physician’s diagnosis of diabetes since their last interview. To validate self-reported diabetes status, we reviewed medical records for a subset of participants (n = 235), with 98% agreement. The analysis reported here was restricted to participants who were diabetes-free at baseline and had complete demographic and follow-up data. Although questions pertaining to diabetes status did not distinguish between type 1 and type 2 diabetes, we further restricted the analysis to adult participants (age 21 years or older; n = 15 975) to assess predominantly type 2 diabetes.
We used two 4-item scales to assess language acculturation, one pertaining to frequency and ability of English usage and the other pertaining to frequency and ability of Spanish usage.8 Scores on each scale ranged from 1 to 4, with a higher score reflecting a greater ability. Scores were then used to place participants into 1 of 3 groups: (1) Spanish-dominant (≥ 2.5 on the Spanish scale only), (2) bilingual (≥ 2.5 on both the English and the Spanish scales), and (3) English-dominant (≥ 2.5 on the English scale only). Participants scoring lower than 2.5 on both scales were excluded from analyses involving language acculturation (n = 142) because the number was too small for meaningful analysis. Birth country and years lived in the United States (among Mexico-born) also were used to assess acculturation.
We used the t test and the χ2 test to compare baseline characteristics between incident diabetes case participants and non–case participants. Cox proportional hazards regression models were fit to investigate the relation between acculturation measures and time to incident diabetes. On the basis of the literature, we performed adjustments for sex, age (continuous), alcohol consumption (current/former or never), smoking status (current/former or never), BMI (< 25.0, 25.0–29.9, ≥ 30.0), sedentary lifestyle (yes/no), and education level (some high school or less, high school graduate, some college, or college graduate). Household income information was not collected from participants enrolled in the cohort prior to September 2004. Thus, additional adjustments for income (< $15 000, $15 000–$34 999, $35 000–$54 999, ≥ $55 000) were performed in only a subset of participants for whom this information was available (n = 8375).
RESULTS
The majority of participants were female (79%) and born in Mexico (77%), and the mean age was approximately 40 years. The median length of follow-up was 5.0 years. Among case participants, the median time to diabetes was 5.3 years (interquartile range = 3.2–7.7). Compared with non–case participants, diabetes case participants were significantly older (P < .001) and more likely to be female (P < .001), to have not graduated from high school (P < .001), to have a sedentary lifestyle (P < .001), and to have a BMI greater than 30.0 (P < .001).
In regression analyses (Table 1), neither language acculturation nor birth country was significantly associated with diabetes risk. Among participants born in Mexico, risk increased with longer duration of US residence. Relative to those with less than 5 years of US residence, risk was significantly elevated among those with 15 to 19 years (hazard ratio [HR] = 1.59; 95% confidence interval [CI] = 1.15, 2.19), 20 to 24 years (HR = 1.58; 95% CI = 1.15, 2.19), and 25 or more years (HR = 1.47; 95% CI = 1.07, 2.01) in the adjusted model (Ptrend = .001). Additional adjustment for income in a subset of participants did not meaningfully change results (data not shown).
TABLE 1—
Hazard Ratios for Developing Diabetes, by Language Acculturation, Birth Country, and Years in the United States: Mexican American Cohort; Houston, TX; 2001–2014
| HR (95% CI) |
||||
| No. Case Participants/No. Non–Case Participants | Unadjusted | Adjusteda | ||
| Language acculturation | ||||
| Spanish dominant | 601/8 738 | 1 (Ref) | 1 (Ref) | |
| Bilingual | 264/4 695 | 0.87 (0.75, 1.00) | 0.95 (0.81, 1.11) | |
| English dominant | 106/1 451 | 0.99 (0.81, 1.22) | 1.00 (0.81, 1.24) | |
| Birth country | ||||
| Mexico | 740/11 490 | 1 (Ref) | 1 (Ref) | |
| United States | 240/3 505 | 0.98 (0.85, 1.13) | 0.89 (0.76, 1.04) | |
| Years in the United States among Mexico-born* | ||||
| < 5 | 59/1 416 | 1 (Ref) | 1 (Ref) | |
| 5–9 | 113/2 594 | 1.22 (0.89, 1.67) | 1.14 (0.83, 1.56) | |
| 10–14 | 136/2 623 | 1.44 (1.06, 1.95) | 1.21 (0.89, 1.64) | |
| 15–19 | 104/1 596 | 2.00 (1.45, 2.75) | 1.59 (1.15, 2.19) | |
| 20–24 | 110/1 152 | 2.17 (1.58, 2.98) | 1.58 (1.15, 2.19) | |
| ≥ 25 | 218/2 108 | 2.43 (1.83, 3.25) | 1.47 (1.07, 2.01) | |
Note. CI = confidence interval; HR = hazard ratio.
Adjusted for age, sex, education, body mass index, sedentary lifestyle, smoking, and alcohol use.
Ptrend < .001 for both the unadjusted and adjusted models.
DISCUSSION
We assessed the relation between acculturation and diabetes risk among Mexican American participants. Language acculturation and birth country were not associated with diabetes risk in this population, but risk increased with years in the United States among participants born in Mexico.
Our finding of an increase in diabetes risk with increasing years in the United States is consistent with results of cross-sectional studies among Hispanic immigrants9 and among immigrants in general.10 Hispanic immigrants typically arrive in the United States with BMIs lower than those of US natives. Over time, however, BMIs tend to converge to native levels,11 thus leading to an increase in diabetes risk. Yet even with adjustment for BMI, the increasing risk with longer duration of residence remained apparent, suggesting that other factors are involved beyond simply increases in body weight with acculturation. These factors may include changes in food availability and diet composition, which may act independently of their effects on BMI. A systematic review found that more acculturated Latino individuals consumed more sugar, fast food, and added fats than did less acculturated individuals.6 Adoption of these unhealthy dietary behaviors over time may increase diabetes risk. Dietary data were not available for these analyses, so we were unable to assess this possibility.
The absence of associations with language acculturation and birth country also has been observed in cross-sectional studies. In a report from the California Health Interview Survey, neither English language ability nor citizenship status was a significant predictor of prevalent diabetes.9 Similar to our findings, however, results from the California Health Interview Survey did indicate an increase in diabetes prevalence with increasing years lived in the United States. Given that acculturation is a complex and dynamic process, different proxy measures may reflect different aspects of acculturation. Among immigrants, years lived in the United States may reflect greater exposure to US diet, sedentary lifestyle, and environmental factors. US birth also may be associated with protective factors, such as access to preventive health services. Language use may be fluid and situational. This suggests that use of a single proxy measure may be inadequate to capture the influence of acculturation in studies of chronic disease outcomes among Hispanic persons.
This study had several limitations. Diabetes risk factors, such as family history and diet, could not be adjusted for in this study. Additionally, because blood measures were not used, we could not detect undiagnosed diabetes outcomes. However, a study that used National Health and Nutrition Examination Survey data reported that undiagnosed disease explains only one third of the recent immigrant advantage for diabetes among Mexican American persons,12 suggesting that immigrants with a longer duration of US residence may remain at increased risk after accounting for undiagnosed disease.
Further studies are needed to examine mediators of the association between acculturation and diabetes risk. Such studies could identify potential intervention targets to reduce diabetes risk among Mexican American individuals.
ACKNOWLEDGMENTS
The cohort receives funds collected pursuant to the Comprehensive Tobacco Settlement of 1998 and appropriated by the 76th legislature to The University of Texas MD Anderson Cancer Center; from the Caroline W. Law Fund for Cancer Prevention; and the Dan Duncan Family Institute for Risk Assessment and Cancer Prevention. C. Anderson was supported by an R25E award from the National Cancer Institute through the Cancer Prevention Research Training Program, MD Anderson Cancer Center.
This study would not have been possible without the generous support and cooperation of the participants, as well as the dedication of the cohort study team. Their continued support is critical to the success of the study.
Note. The funders did not contribute to the design and conduct of the study; the collection, analysis, or interpretation of the data; or the preparation, review, or approval of the brief.
HUMAN PARTICIPANT PROTECTION
This study was approved by the institutional review board of the University of Texas MD Anderson Cancer Center.
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