Smoking Trajectories among Koreans in Seoul and California: Exemplifying a Common Error in Age Parameterization

Jon-Patrick Allem,Melbourne F Hovell,Jennifer B Unger,John W Ayers,Veronica L Irvin,C Richard Hofstetter

doi:10.7314/apjcp.2012.13.5.1851

Jon-Patrick Allem, Melbourne F Hovell + Show 4 more

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https://doi.org/10.7314/apjcp.2012.13.5.1851

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Abstract

Immigration to a nation with a stronger anti-smoking environment has been hypothesized to make smoking less common. However, little is known about how environments influence risk of smoking across the lifecourse. Research suggested a linear decline in smoking over the lifecourse but these associations, in fact, might not be linear. This study assessed the possible nonlinear associations between age and smoking and examined how these associations differed by environment through comparing Koreans in Seoul, South Korea and Korean Americans in California, United States. Data were drawn from population based telephone surveys of Korean adults in Seoul (N=500) and California (N=2,830) from 2001-2002. Locally weighted scatterplot smoothing (lowess) was used to approximate the association between age and smoking with multivariable spline logistic regressions, including adjustment for confounds used to draw population inferences. Smoking differed across the lifecourse between Korean and Korean American men. The association between age and smoking peaked around 35 years among Korean and Korean American men. From 18 to 35 the probability of smoking was 57% higher (95%CI, 40 to 71) among Korean men versus 8% (95%CI, 3 to 19) higher among Korean American men. A similar difference in age after 35, from 40 to 57 years of age, was associated with a 2% (95%CI, 0 to 10) and 20% (95%CI, 16 to 25) lower probability of smoking among Korean and Korean American men. A nonlinear pattern was also observed among Korean American women. Social role transitions provide plausible explanations for the decline in smoking after 35. Investigators should be mindful of nonlinearities in age when attempting to understand tobacco use.

Highlights

Immigration to a nation with a stronger anti-smoking environment has been hypothesized to make smoking less common (Zhu et al, 2007)
The association between age and smoking peaked around age 35 among Korean and Korean American men (Figure 1A)
Increases in age trended toward a higher probability of smoking until about 35 and thereafter increases in age trended toward a lower probability of smoking

Summary

Introduction

Immigration to a nation with a stronger anti-smoking environment has been hypothesized to make smoking less common (Zhu et al, 2007). Little is known about how environments influence risk of smoking across the lifecourse (Constantine et al, 2010; Kuh et al, 2003). The Korean and Korean American populations provide excellent case studies for evaluating such questions as the two populations each reside in regions with distinct socio-cultural contexts e.g., different tobacco control policies and social norms pertaining to smoking. Demographic traits, such as age, have strong theoretical associations with health (Link & Phelan, 1995) but research suggested age is often employed as a predictor without meaningful rationale e.g., creating a dummy indicator for young versus old This study assessed the possible nonlinear associations between age and smoking and examined how these associations differed by environment

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