POPULATION-BASED ANALYSIS OF THE EFFECT OF THE NORTHRIDGE EARTHQUAKE ON CARDIAC DEATH IN LOS-ANGELES-COUNTY, CALIFORNIA

Objectives. We sought to determine whether a natural disaster affected total cardiovascular mortality and coronary mortality in an entire po pulation. Background. The effect of the January 17, 1994 Northridge Ea rthquake (NEQ) on all deaths and causes of deaths within the entire po pulation of Eus Angeles County is unknown. The purposes of our study w ere to analyze all deaths in this entire population before, during and after the NEQ and to determine whether the NEQ temporally and spatial ly altered death due to cardiovascular disease. Methods. We analyzed a ll death certificate data (n = 19,617) from Los Angeles County during January of 1992, 1993 (control periods) and 1994, using International Classification of Diseases, 9th Revision codes for ischemic beast dise ase (IHD) and atherosclerotic cardiovascular disease (ASCVD), as well as other causes of death. Results. There was an average of 73 deaths p er day due to IHD and ASCVD during January 1 to 16, 1994; this increas ed to 125 on the day of the NEQ, and then decreased to 57 deaths per d ay from January 18 to 31 (p < 0.00001, before NEQ vs, day of NEQ; afte r NEQ vs, day of NEQ; and before NEQ vs. after NEQ). The NEQ was assoc iated with an increase in deaths due to myocardial infarction and trau ma but not cardiomyopathy, hypertensive heart disease, valvular heart disease, cerebrovascular disease or noncardiovascular causes. Based on plots of daily deaths due to IHD and ASCVD, the decrease in deaths du ring the 14 days after the NEQ (-144) overcompensated for the increase on the day of the NEQ (+55). Geographic analysis revealed a redistrib ution of deaths due to IHD and ASCVD toward the epicenter on the day o f the NEQ. Conclusions. When an entire population simultaneously exper iences a major environmental stress, there is an increase in death doe to coronary artery disease (but not other cardiac causes), followed b y a decrease that overcompensates for the excess of death. The overcom pensation may represent a residual population that is more resistant t o stress or a possible preconditioning effect of the stress, or both. This study supports the concept that cardiovascular events within an e ntire population can be triggered by a shared stress. (C) 1997 by the American College of Cardiology.