Elsevier

Preventive Medicine

Volume 73, April 2015, Pages 15-21
Preventive Medicine

Longitudinal study of acculturation and BMI change among Asian American men

https://doi.org/10.1016/j.ypmed.2015.01.009Get rights and content

Highlights

  • We examined the acculturation-overweight association in Asian Americans.

  • We examined the acculturation-BMI change association in Asian Americans.

  • Less acculturated Asians had lower odds of overweight.

  • Less acculturated Asians had larger BMI increases over time.

  • Interventions preventing weight gain in recent Asian immigrants are needed.

Abstract

Background

Cross-sectional studies examining the association between Western acculturation and BMI in Asians have been inconsistent, and studies on BMI change are lacking.

Objective

This study examined the associations between indicators of acculturation (generational status, length of US residence, and age at immigration) and overweight (BMI ≥ 25 kg/m2) as well as 5-year BMI changes in 7,073 Chinese, Japanese, Korean, Filipino, and Vietnamese men who lived in the US and were 44–71 years old at baseline of the California Men's Health Study (2002–2003).

Methods

Indicators of acculturation were reported at baseline. Repeated clinical measures of BMI were extracted from electronic health records (2005–2012).

Results

Using generalized estimating equations we found that lower generational status, shorter duration of US residence and older age at immigration were inversely associated with being overweight. However, analysis of BMI curves using linear mixed models showed that shorter length of US residence and older age at immigration were associated with larger 5-year increases in BMI.

Conclusions

Asian immigrants who were less acculturated had larger BMI increases as they became more acculturated but had not achieved overweight status. Healthy weight interventions among Asians immigrants may be most effective when targeting weight maintenance early in the process of acculturation.

Introduction

Asians living in the US (Asian Americans) have a higher prevalence of overweight and obesity compared to Asians living in their ancestral countries (Schiller et al., 2012, Stevens et al., 2012). These differences may be explained by exposure to a Western environment and acculturation, the process of adopting cultural traits of the host country (Berry, 1997). However, cross-sectional studies examining the association between acculturation and body mass index (BMI) in Asian immigrants to Western countries have been inconsistent. Some studies found no association (Park et al., 2008, Kaushal, 2009, Huang et al., 1996), while others found a positive association (Gomez et al., 2004, Klatsky and Armstrong, 1991, Oza-Frank and Narayan, 2010, Cairney and Ostbye, 1999, Bates et al., 2008). The authors of most studies combined all Asians and do not account for potential heterogeneity between Asian subgroups (Salant and Lauderdale, 2003). Similarly, among Latinos, it has been shown that combining subgroups can cause methodological problems (Umaña-Taylor and Fine, 2001). Additionally, BMI examined in cross-sectional studies might have been the same since pre-migration. Longitudinal studies on BMI change could clarify the previous contradictory results by assuring that the observed changes in BMI associated with different levels of acculturation occurred after immigration.

The obesity epidemic in the US has been linked to consumption of energy-dense foods and physical inactivity, characteristics of an obesogenic environment (Hill and Peters, 1998). Acculturation to these norms may have detrimental effects on the health of Asian immigrants (Horgen and Brownell, 2002). A pioneering study of the health consequences of American acculturation in Asians is the Honolulu Heart Program, which approximately 50 years ago recruited 8,006 men of Japanese ancestry living in Hawaii (Huang et al., 1996, Reed et al., 1982). A higher level of maintenance of Japanese culture, measured using three self-reported scales (culture of upbringing, current cultural assimilation, and current social assimilation), was related to lower levels of BMI in a cross-sectional analysis (26 vs. 23 kg/m2 in lowest vs. highest quartile, P < 0.05). Contrary to expectation, Japanese born in Hawaii did not have a significantly different mean BMI compared to those born in Japan. This may be because data were collected prior to the US obesity epidemic, which was first detected in the late 70s (Flegal et al., 1998). More recently, there have been huge transitions in the economy, lifestyles, and obesity prevalence in many Asian countries (Popkin, 1994). Therefore, early research has limited application to recent waves of Asian immigrants to the US.

Our study determined associations of measures of acculturation (generation, length of US residence, and age at immigration), indicating an immigrant's exposure to the Western environment, with overweight (≥ 25 kg/m2) and longitudinal changes in BMI among Asian men. We also sought to examine potential heterogeneity within the Asian population by analyzing results for Asian subgroups separately (Chinese, Japanese, Koreans, Filipino, and Vietnamese). To our knowledge, this is the first study that has used serial assessments of measured BMI to examine the impact of Western acculturation in Asians.

Section snippets

Study population

The California Men's Health Study is a prospective cohort initiated by Kaiser Permanente Northern and Southern California in 2002–2003 (Enger et al., 2006). Eligible participants were males aged 44–71 years who had been Kaiser Permanente members for at least 1 year prior to study enrollment. Participants reported their race/ethnicity on a screening survey prior to the baseline survey. This information was used to create unique racial/ethnic categories for the following: Chinese, Japanese, Korean,

Results

At baseline, participants of each Asian subgroup were on average between 58 and 60 years old (Table 1). Less than 10% of Japanese, Koreans, and Filipinos but almost one-quarter of Vietnamese had less than a high school degree. Similarly, one-third of Vietnamese had an annual household income of < $40,000, while the proportion was lower in the other subgroups. The majority of Chinese, Koreans, Filipinos, and Vietnamese were foreign-born, while only 16.5% of Japanese were foreign-born. With the

Discussion

It has been hypothesized that Western acculturation is associated with higher BMI, but previous studies have been inconsistent (Park et al., 2008, Kaushal, 2009, Huang et al., 1996, Gomez et al., 2004, Klatsky and Armstrong, 1991, Oza-Frank and Narayan, 2010, Cairney and Ostbye, 1999, Bates et al., 2008). Our longitudinal study provided further insight as it allowed the examination of BMI change. First-generation, foreign-born Asian men had a healthier BMI than second- or third-generation,

Conclusion

This study makes an important contribution to the literature by showing differences in BMI by levels of acculturation longitudinally and across Asian subpopulations. The results greatly enhance our understanding of overweight risk in Asian Americans by pointing out that foreign-born Asian immigrants and especially those who recently immigrated are particularly susceptible to excess increases in BMI. Interventions focused on weight maintenance need to be targeted towards new immigrants when

Conflict of interest

The authors declare that there are no conflicts of interest.

Acknowledgments

The cohort was established with funds from the California Cancer Research Program, grant no. 99-86883, and the Kaiser Permanente Northern California Community Benefit Program. These analyses were supported by the Kaiser Permanente Southern California Community Benefit Program. The authors acknowledge the contributions of California Men's Health Study scientists, including Dr. Stephen Van Den Eden, and study staff, especially Jeff Slezak and Dr. Margo Sidell. The authors would also like to thank

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