What was done
Daily counts of deaths from all causes, excepting violent deaths and neonatal deaths up to one month of age, were extracted from Sao Paulo's mortality information system for the period 1991-1994 and analyzed for the age groups less than 15 years (children), 15-64 years (adults), and greater than equal to 65 years (elderly) with respect to the effects of temperature.  As a part of these analyses, "change points" were determined at which heat and cold effects started.

What was learned
The authors determined that the change points for both heat- and cold-induced deaths were identical, i.e., 20°C.  For each 1°C increase above this value for a given and prior day's mean temperature, they observed a 2.6% increase in deaths from all causes in children, a 1.5% increase in deaths from all causes in adults, and a 2.5% increase in deaths from all causes in the elderly.  For each 1°C decrease below the 20°C change point, however, the cold effect was greater, with increases in deaths from all causes in children, adults and the elderly registering 4.0%, 2.6% and 5.5%, respectively.  These cooling-induced death rates were 54%, 73% and 120% greater than those attributable to warming.

A similar analysis with respect to only cardiovascular deaths actually found no evidence of heat-induced deaths in adults but the familiar 2.6% increase for each 1°C decrease below 20°C.  In the elderly, however, a 1°C warming above 20°C led to a 2% increase in deaths; but a 1°C cooling below 20°C led to a 6.3% increase in deaths in this age group, or more than three times as many cardiovascular-related deaths due to cooling than to warming in the elderly.

Findings with respect to respiratory-induced deaths were similar.  Death rates due to a 1°C cooling were twice as great as death rates due to a 1°C warming in adults, and 2.8 times greater in the elderly.

What it means
When it comes to the bottom-line reality of living or dying, it is clear that a modest warming of the climate would be preferable to a modest cooling or even no change at all, not only in Sao Paulo, Brazil, but in all the many other places of the world where similar studies have found essentially the same results as those described in this study [see, for example, Health Effects (Cardiovascular, Cold Weather, Hot Weather, Respiratory) in our Subject Index].