Title Trends in mortality from septicaemia and pneumonia witheconomic development : An age-period-cohort analysis

Background: Hong Kong population has experienced drastic changes in its economic development in the 1940s. Taking advantage of Hong Kong’s unique demographic and socioeconomic history, characterized by massive, punctuated migration waves from Southern China, and recent, rapid transition from a pre-industrialized society to the first ethnic Chinese community reaching ‘‘first world’’ status over the last 60 years (i.e., in two or three generations), we examined the longitudinal trends in infection related mortality including septicemia compared to trends in non-bacterial pneumonia to generate hypotheses for further testing in other recently transitioned economies and to provide generalized aetiological insights on how economic transition affects infection-related mortality. Methods: We used deaths from septicemia and pneumonia not specified as bacterial, and population figures in Hong Kong from 1976–2005. We fitted age-period-cohort models to decompose septicemia and non-bacterial pneumonia mortality rates into age, period and cohort effects. Results: Septicaemia-related deaths increased exponentially with age, with a downturn by period. The birth cohort curves had downward inflections in both sexes in the 1940s, with a steeper deceleration for women. Non-bacterial pneumoniarelated deaths also increased exponentially with age, but the birth cohort patterns showed no downturns for those born in the 1940s. Conclusion: The observed changes appeared to suggest that better early life conditions may enable better development of adaptive immunity, thus enhancing immunity against bacterial infections, with greater benefits for women than men. Given the interaction between the immune system and the gonadotropic axis, these observations are compatible with the hypothesis that upregulation of the gonadotropic axis underlies some of the changes in disease patterns with economic development. Citation: Wong IOL, Cowling BJ, Leung GM, Schooling CM (2012) Trends in Mortality from Septicaemia and Pneumonia with Economic Development: An AgePeriod-Cohort Analysis. PLoS ONE 7(6): e38988. doi:10.1371/journal.pone. 0038988 Editor: Thomas A. Smith, Swiss Tropical & Public Health Institute, Switzerland Received March 27, 2012; Accepted May 17, 2012; Published June 14, 2012 Copyright: 2012 Wong et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: BJC was supported by the Harvard Center for Communicable Disease Dynamics from the National Institute of General Medical Sciences (grant no. U54 GM088558). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: BJC received research funding from MedImmune Inc., and consults for Crucell MV. BJC is an Academic Editor of the journal PLoS ONE. This does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials. The other authors have declared that no competing interest exist. * E-mail: cms1@hkucc.hku. hk