Various stressors trigger cardiac death. The objective was to investigate a possible relation between a stock market crash and cardiac death in a large population within the United States. We obtained daily stock market data (Dow Jones Industrial Average Index), death certificate data for daily deaths in Los Angeles County (LA), and annual LA population estimates for 2005 through 2008. The 4 years death rate curves (2005 through 2008) were averaged into a single curve to illustrate annual trends. Data were “deseasonalized” by subtracting from the daily observed value the average value for that day of year. There was marked seasonal variation in total and cardiac death rates. Even in the mild LA climate, death rates were higher in winter versus summer including total death (+17%), circulatory death (+24%), coronary heart disease death (+28%), and myocardial infarction death (+38%) rates (p <0.0001 for each). Absolute coronary heart disease death rates have decreased since 1985. After accounting for seasonal variation, the large stock market crash in October 2008 did not affect death rates in LA. Death rates remained at or below seasonal averages during the stock market crash. In conclusion, after correcting for seasonal variation, the stock market crash in October 2008 was not associated with an increase in total or cardiac death in LA. Annual coronary heart disease death rates continue to decrease. However, seasonal variation (specifically winter) remains a trigger for death and coronary heart disease death even in LA where winters are mild.
Stressful events affecting large populations provide unique opportunities to explore the relation among triggers, emotions, and cardiovascular events. Cardiovascular deaths have increased in relation to missile attacks, earthquakes, and even high-stakes soccer and football matches. A large downturn in the stock market causes mental stress on much of the general population, but it is not known whether a stock market crash affects cardiovascular mortality in a large population. This project investigated a possible relation between cardiac deaths and the stock market crash in autumn 2008 in Los Angeles County (LA).
Methods
From 2005 through 2008, we obtained annual LA population estimates (population estimates also obtained for 2004 and 2009), daily stock market data (Dow Jones Industrial Average Index, available at: http://moneycentral.msn.com/investor/charts/chartdl.aspx?symbol=%24INDU&CP=0&PT=9” >), and daily death certificate data from the LA Department of Health Services Data Collection and Analysis Unit. We analyzed separately all deaths (total deaths from all causes) and 3 groups of cardiac deaths based on the International Classification of Diseases, Tenth Revision (ICD-10) codes for all circulatory deaths (ICD-10 codes I00 through I99), coronary heart disease deaths (ICD-10 codes I20 through I25), and acute myocardial infarction deaths (ICD-10 codes I21). All deaths of LA residents are reported to the Department of Health Services Data Collection and Analysis Unit and are included in the dataset. Causes of death are coded by the attending physician or coroner.
Assuming a constant population change per year, daily deaths were converted to daily death rates per a 100,000 population. The death rate data were “smoothed” by converting daily rates into 11-day centered moving averages (mean of daily rates over 11 days including the observed day and the 5 days before and after). The 4 years smoothed curves (2005 through 2008) were averaged into a single curve to illustrate an average seasonal behavior in death rates (i.e., day x on the average seasonal behavior curve was the median of the 4 [2005 through 2008] 11-day average values centered on day x). The data were then “deseasonalized” by subtracting from each daily value on the smoothed curve the average value for that day of year, specifically looking for large deviations during the stock market crash. Deseasonalization uncovers observed death rates that deviated from average seasonal behavior. Raw daily death rates were also compared to average seasonal behavior.
Raw daily death rates were compared in winter (December and January) versus summer (June through September) using nonparametric Wilcoxon 2-sample tests. A p value <0.05 was considered statistically significant.
Results
Raw data are depicted in Figure 1 . There was marked seasonal variation in daily death rates in LA, which is notable for its moderate weather and modest temperature fluctuations ( Figure 2 ). Death rates were higher in winter versus summer including total death (+17%), circulatory death (+24%), coronary heart disease death (+28%), and myocardial infarction death (+38%, p <0.0001 for each). The shape of the annual death rate curves (“U” shape) has not changed since our initial description of this phenomenon for the 1980s.
Although the annual variation in death rates has not changed since the 1980s, the absolute coronary heart disease death rates have decreased since 1985 including from 2005 through 2008 ( Table 1 ).
| Year | Coronary Heart Disease Deaths | LA Population | Coronary Heart Disease Death Rate |
|---|---|---|---|
| 1985 | 19,510 | 8,018,210 | 0.243% |
| 1996 | 16,411 | 9,499,563 | 0.173% |
| 2005 | 14,365 | 10,219,477 | 0.141% |
| 2008 | 12,580 | 10,418,695 | 0.121% |
After accounting for seasonal variation, the stock market crash in October 2008 was not associated with an increase in total or cardiac deaths in LA. Figure 3 depicts the raw daily death rates in 2008 superimposed on average seasonal behavior. Figure 4 shows deseasonalized death rates. Severe decreases in the Dow Jones Industrial Average Index, including the large crash in early October 2008, did not correlate with higher than expected death rates (i.e., death rates remained at or below the seasonal average).
