What was done
The authors tabulated all 222,265 death certificates from Los Angeles County, California, for deaths caused by coronary artery disease as a function of month of the year from 1985 through 1996.

What was learned
The authors found that "even in the relatively mild climate of southern California, there is a seasonal variability to coronary death, with rates in December and January 33% higher than in June through September."  They additionally noted that studies from a number of other locations have also determined that deaths due to coronary artery disease are more prevalent in the colder winter months of the year than they are in the warmer summer months.

What it means
This study provides further support for the growing body of evidence that indicates that cooler weather is more conducive to the occurrence of death due to coronary artery disease than is warmer weather, even in a climate where it does not get very cold.  Hence, it naturally follows that global warming, if it occurs in the future, is likely to be beneficial to much of humanity by reducing the incidence of death due to coronary artery disease, which is a major cause of death the world over.