LONG- AND MEDIUM-TERM UBIQUITOUS ENVIRONMENTAL EXPOSURES AND SUDDEN CARDIAC DEATH

Abstract

Sudden cardiac death (SCD) is a common manifestation of cardiovascular disease (CVD) which is underappreciated in the CVD literature. Investigations into the CVD risk factors which contribute to SCD have yielded little additional information, and in the majority of the people who succumb to SCD, there are no previous signs or symptoms of CVD. Most of the previously published information on SCD investigates the hours and days leading up to the event but falls short of examining medium- and long-term exposures and SCD. Therefore, the goal of this dissertation was to investigate three ubiquitous environmental exposures and their association with SCD in the medium- and long-term. Prior to engaging in original research, the first paper (Chapter 2) serves as a systematic and in-depth review of the previously published literature on air pollution, temperature, and altitude with SCD. Air pollution, especially particulate air pollution (PM) and ozone, were consistent contributors to OHCA/SCD in the short-term. Likewise, both cold and warm temperatures were associated with OHCA/SCD in the short-term, with effect estimates generally being larger for colder temperatures. All three of the original research papers used time-varying Cox-proportional hazards models to investigate the relationship between the three exposures and SCD. The first original research paper (Chapter 3) focused on an important criteria pollutant, PM, and SCD. PM2.5 and PM2.5-10 both were associated with SCD at different time windows. The second original research paper (Chapter 4) investigated the relationship between 1-month moving average temperature and 12-month moving average temperature and SCD, and it determined that there was an association between both moving averages and SCD. The third original research paper (Chapter 5) addressed a major gap in the literature on altitude and SCD in that there are no studies that investigate the association between altitude of residence and SCD in the general population. Although the association was ultimately null, this result helped clarify that the cardiovascular benefits attributed to altitude in terms of incident myocardial infarction and mortality do not extend to SCD. This dissertation represents an important contribution to the environmental epidemiology and cardiology literature on ubiquitous environmental exposures and SCD. Climate change and pollution are major contributors to CVD mortality, including SCD. Therefore, mitigation strategies both in the US and worldwide are necessary to ameliorate the burden of CVD which is attributable to SCD. Since there is a very narrow time window for treatment of a fatal arrhythmia prior to deteriorating into SCD, population-level interventions to lessen the burden of environmental exposures are critical to reducing SCD.