Neighbourhood and Mortality Table 4. Hazard Ratios (95% Confidence Intervals) from Survival Analyses for Cancer Deaths by Neighbourhood SES Category Quintiles for CAD Patients (n = 485) After 13.3 Years Follow-Up Time Survival model without covariates Survival model with covariates: Step 1 Step 2 SES quintile Age (years) Male sex BMI SES quintile Covariates in Models Education Smoking (ever or current) 3.25 (1.11–9.51)* 1.11 (0.88–1.41) 1.05 (1.01–1.09)* 0.99 (0.40–2.43) 0.97 (0.89–1.05) 1.18 (0.94–1.48) Unemployment 1.56 (1.16–2.11) { 1.05 (1.01–1.10)* 1.01 (0.41–2.48) 0.97 (0.89–1.06) 2.98 (1.02–8.76)* 1.62 (1.20–2.19) { Median Family Income 1.40 (1.07–1.83)* 1.04 (1.00–1.09)* 1.05 (0.43–2.59) 0.97 (0.89–1.06) 3.19 (1.06–9.33)* 1.42 (1.09–1.84) { Hazard ratios, 95% confidence intervals, and significance values for each quintile increase in SES indices are given from Cox regression models for risk of cancer mortality. Covariates listed were force-entered in adjusted Cox regression models. *p#0.05 {p#0.01 SES = socioeconomic status; BMI = body mass index doi:10.1371/journal.pone.0004120.t004 biological perturbations may accumulate over time in a manner that contributes to the development and/or progression of chronic diseases such as cancer [38,39], and the findings of our study are consistent with this theory. Limitations This study has limitations that need to be considered. Individual-level socioeconomic information was not collected at baseline. Thus, we are unable to take this data into account when evaluating neighbourhood socioeconomic effects, or to compare the magnitude of individual- versus neighbourhood-level socio- economic gradients. Both patient self report and measurements at baseline were used to gather information about risk factors. These approaches are subject to recall bias and measurement error, respectively. Also, our participants were not asked about personal history of cancer at initial baseline assessment. Thus, despite other Figure 2. Survival curve for cancer mortality by quintile of neighbourhood unemployment for 485 coronary artery disease patients after 13.3 years follow-up time. Quintiles of neighbourhood unemployment are relative to 469 neighbourhoods in the province of British Columbia mapped from the Human Early Learning Partnership mapping project, with unemployment data derived from Statistics Canada 2001 census. Higher quintiles represent increasing levels of neighbourhood unemployment. Survival curves are derived from Cox regression survival analyses with adjustment for age, sex, body mass index, and smoking history. doi:10.1371/journal.pone.0004120.g002 PLoS ONE | www.plosone.org 7 January 2009 | Volume 4 | Issue 1 | e4120