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Exposure to urban life and mortality risk among older adults in China

sometimes used for the same counties/cities over time. Consequently, migration as
indicated by survey data may not happen with actual geographic mobility. Although
we have incorporated PLO and migration that could partially capture the difference
between those who actually migrated and those who did not, these issues may still
cause bias. It would be ideal to collect data from each individual to distinguish in situ
urbanization and urbanization due to geographical migration within and beyond the
home county.
Third, specific contextual factors that are associated with health/mortality were
not included in the present study due to unavailability of data. The linkage between
urbanization and health is complex in that it involves multiple processes along
environmental, socioeconomic, epidemiological, spatial, behavioral, and psychological
dimensions (Gong, Liang, Carlton, et al., 2012). Environmental quality and healthcare
services are also associated with health outcomes (Zeng, Gu, Purser, et al., 2010;
Zhang, Dupre, Qiu, et al., 2017). In that regard, incorporation of specific physical and
social contextual factors is necessary to better reveal the mechanisms between urban
exposure and mortality (Wen and Gu, 2011).
Despite these shortcomings, our findings shed new light on urban-rural health
disparity in China, with implications for future research in this important field.
As proposed in this study, multiple urban-rural residential transitions over the life
course, rather than status at birth, current residential status, or rural-urban migration,
should be highlighted in future studies to better identify key aspects in the process of
urbanization that are beneficial or detrimental to health (Gong, Liang, Carlton, et al,
2012). The study results are also informative for those countries, similar to China,
that are undergoing significant urbanization, population aging, and epidemiological
transition; however, interpretation of the impacts of urban exposure on mortality
should always consider specific contexts and histories.

Authors’ Contribution
D Gu designed the study, supervised the analysis, drafted and revised the manuscript.
Q Feng and JM Sautter revised the manuscript and interpreted the results. L Qiu
prepared the data and performed the analysis.
Conflict of Interest

No conflict of interest has been reported by the authors.
Ethics Approval

No ethics approval was required for this study. The datasets were obtained from a
publicly accessible database of the Chinese Longitudinal Healthy Longevity Survey
at the National Archive of Computerized Data on Aging, University of Michigan
(http://www.icpsr.umich.edu/icpsrweb/NACDA/studies/36179) with a signed data use
agreement.

Funding

The authors declare that they have no financial support for this study.
Acknowledgements

The authors would like to thank the two reviewers for their helpful comments.

Disclaimer
Views expressed in this article are solely those of the authors and do not necessarily
reflect those of the United Nations, National University of Singapore, and University
of the Sciences.

16 International Journal of Population Studies 2017, Volume 3, Issue 1