Living in areas with different levels of earthquake damage and association with risk of cardiovascular disease: a cohort-linkage study.

BACKGROUND: Cardiovascular disease rates are known to increase immediately after a severe earthquake. However, less is known about the magnitude of this increase over time in relation to the amount of housing damage. We assessed the effect of area housing damage from a major earthquake sequence in Christchurch, Canterbury province, New Zealand, on cardiovascular disease-related hospital admissions and deaths.
METHODS: For this cohort-linkage study, we used linked administrative datasets from the Statistics New Zealand Integrated Data Infrastructure to identify individuals aged 45 years or older living in Christchurch from the date of the first earthquake on Sept 4, 2010. Individuals were assigned the average damage level for their residential meshblock (small neighbourhood generally comprising 10-50 dwellings) using the insurance-assessed residential building damage costs obtained from the Earthquake Commission as a proportion of property value. We calculated the rates of cardiovascular disease-related hospital admissions (including myocardial infarction) and cardiovascular disease-related mortality and rate ratios (adjusted for age, sex, ethnicity, small-area deprivation index, and personal income) by level of housing damage in the first year and the 4 subsequent years after the earthquake. The rate ratio association between earthquake housing damage and cardiovascular event was examined by Poisson regression, and linear test of trends across damage categories was done by regression modeling.
FINDINGS: We identified 179 000 residents living in the earthquake-affected region of Christchurch, of whom 148 000 had complete data. For the first 3 months after the Feb 22, 2011 earthquake, the Poisson regression-adjusted rate ratio (RR) for cardiovascular disease-related hospital admissions for residents from areas that were most damaged (compared with residents from the least damaged areas) was 1·12 (95% CI 0·96-1·32; test for linear trend p=0·239). In the first year after the earthquake sequence, for residents from areas that were most damaged (vs the least damaged areas), Poisson regression-adjusted RRs were 1·10 (1·01-1·21; test for linear trend p=0·068) for cardiovascular disease-related hospital admissions, 1·22 (1·00-1·48; p=0·036) for myocardial infarction-related hospital admissions, and 1·25 (1·06-1·47; p=0·105) for cardiovascular disease-related mortality, corresponding to an excess of 66 (95% CI 7-125) cardiovascular disease-related hospital admissions, including 29 (0-53) additional myocardial infarction-related hospital admissions and 46 (13-73) additional deaths from cardiovascular disease. In the 4 subsequent years, we found no evidence of an association of these outcomes with earthquake damage.
INTERPRETATION: Rates of cardiovascular disease and myocardial infarction were increased in people living in areas with more severely damaged homes in the first year after a major earthquake. Policy responses to reduce the effect of earthquake damage on cardiovascular disease could include pre-earthquake measures to minimise building damage, early wellbeing interventions within the first year to address post-earthquake stress, and enhanced provision of cardiovascular disease prevention and treatment services. FUNDING: Healthier Lives National Science Challenge and Natural Hazards Research Platform, Ministry of Business, Innovation and Employment.