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Seasonal Variation of Total and Cardiac Death Rates Across Different Climates

Seasonal Variation of Total and Cardiac Death Rates Across Different Climates. Bryan G. Schwartz, MD 1 Robert A. Kloner , MD, PhD 1,2 1 Heart Institute, Good Samaritan Hospital; 2 Department of Internal Medicine, Division of Cardiovascular Medicine,

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Seasonal Variation of Total and Cardiac Death Rates Across Different Climates

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  1. Seasonal Variationof Total and Cardiac Death Rates Across Different Climates Bryan G. Schwartz, MD1 Robert A. Kloner, MD, PhD1,2 1Heart Institute, Good Samaritan Hospital; 2Department of Internal Medicine, Division of Cardiovascular Medicine, Keck School of Medicine at the University of Southern California, Los Angeles, California USA

  2. # of CAD Deaths Degrees F

  3. Seasonal Variation – Prior studies Wolf. Circ 2009;120:735 Danet. Circ 1999;100:e1 Gerber. JACC 2006;48:287 Cech. Israel J Med Sci 1977;13:451 Weerasinghe. Heart 2002;88:30 Bhaskaran. Heart 2009;95:1760

  4. Seasonal Variation – Methods • Obtain daily death certificate data from 2005-08 for a variety of climates, compare seasonal patterns • Hot: Texas (24 million), Georgia (9), Maricopa County (4) • Moderate: Los Angeles County (10), West ½ of Washington (5) • Cold: Massachusetts (6.5), Pennsylvania (12.5) • Death certificate data from state health departments • Total deaths, Circulatory deaths, Ischemic heart disease deaths • Population data from US Census Bureau

  5. Average Seasonal Apparent Temperature in Texas, Pennsylvania and Los Angeles Ave Seasonal Apparent Temp (°C) 40 30 20 10 0 TX temp LA temp PA temp 1/1 4/1 7/1 10/1 12/31

  6. Seasonal Variation – Hypothesis • The winter peak in death rates would be greater in climates with colder winters

  7. Seasonal Variation – Methods • Converted daily number of deaths to daily death rates (assuming constant population change) Los Angeles County: population 10 million • Average seasonal values for each day of year: • 19-day centered moving average • Median of 4 years’ daily value

  8. Average Circulatory Death Rate Circulatory Death Rate (per 100,000 population/day) 1/1 4/1 7/1 10/1 12/31

  9. Seasonal Variation – Methods • Calculated variation around the mean: • Daily death rate / average daily death rate • Daily % change from average annual death rate

  10. Normalized Circulatory Death Rate +20% +10% average -10% -20% Daily % Change from Average 1/1 4/1 7/1 10/1 12/31

  11. Seasonal Variation – Methods • Average seasonal curves were used to identify the peak and trough 8-day periods • Using the raw daily death rates, calculated maximum % change: • Peak values – trough values = maximum % change (32 values) • Compared maximum % change using one-way ANOVA

  12. Maximum Percent Change in 7 Different Climates Maximum % Change 40% 35% 30% 25% 20% P=0.54 ANOVA P=0.54 TX AZ GA LA WA PA MA

  13. Seasonal Variation – Conclusions • The U shaped curve of circulatory death rates was very similar in 7 locations studied with different climates • Circulatory death rates are 26-36% higher during the winter • Explanations: • People acclimate to their local climate • Other factors influence seasonal variation of circulatory death rates • Habits: diet, exercise, weight • Hours of daylight: depression • Respiratory infection

  14. Citations • Kloner RA, et al. Circulation 1999;100:1634. • Wolf. Circulation 2009;120:735 • Danet. Circulation 1999;100:e1 • Gerber. J Am Coll Cardiol 2006;48:287 • Cech. Israel J Med Sci 1977;13:451 • Weerasinghe. Heart 2002;88:30 • Bhaskaran. Heart 2009;95:1760

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