Background
The authors write that "weather and climate changes are associated with a number of immediate and long-term impacts on human health that occur directly or indirectly, through mediating variables," yet they say that "few studies to date have established the empirical relationship between monthly weather and mortality in sub-Saharan Africa," which is what they thus proceed to do.

What was done
Working with mortality data obtained from the Rufiji (Tanzania) Health and Demographic Surveillance System (RHDSS) for the period 1999 to 2010, Mrema et al. employed time-series Poisson regression models to estimate the association between monthly temperature - which ranges from 27.9 to 34.4°C in this tropical region - and mortality adjusted for long-term trends in three different age groups (0-4, 5-59, 60+).

What was learned
In the words of the four Tanzanian researchers, "mortality in all age groups peaked up at the mid of the year," which is "the time when the temperature is relatively lower compared to other periods of the year in Rufiji." In fact, they say that if the monthly average temperature drops to a value of 24°C from the threshold, "mortality will increase by 80.7%, 65.7% and 74% in age groups 0-4, 5-59 and over 60, respectively."

What it means
In discussing their findings, Mrema et al. note that "Rufiji's population is accustomed to a tropical climate and, like any other population, is exposed to cold temperatures relative to its average climate [italics added]." And so it is that in warm and cold climates alike, it is relative cold that kills far more people than relative heat, as may readily be verified by perusing the many reviews of this subject that are archived under the heading of Health Effects - Temperature: Hot vs. Cold Weather in our Subject Index.