Acknowledgments—This study was supported by Seoul City Research and Business
Development program (10526), Seoul, Korea.
No potential conflicts of interest relevant to
this article were reported.
S.H.J. analyzed data and wrote the manuscript. A.W.F. and J.M.S. contributed to discussion and reviewed/edited the manuscript.N.W.H. provided input to data analysis and
reviewed/edited the manuscript.
We thank the staff of the Korean National
Health Insurance Corporation. The Johns
Hopkins Bloomberg School of Public Health is
one of five partner organizations of the
Bloomberg Initiative; its mission is to promote
freedom from smoking worldwide.