Are mortality rates for respiratory diseases in the RSA affected by climate?

Age-standardized and age-specific mortality rates (MRs)/100 000 of whites for the pneumonias and chronic respiratory diseases averaged over the 3-year period 1979-1981 for four highveld cities, Johannesburg, Bloemfontein, Pretoria and Germiston, were compared with those for four coastal cities, Cape Town, Durban, Port Elizabeth and East London--Durban being in the subtropics. The highveld cities have cold winter climates with air temperatures falling to freezing point in June and July, whereas the winters are mild in the coastal cities. In Durban, for example, the mean minimum monthly air temperature rarely falls below 10 degrees C in winter. Age-standardized MRs for the pneumonias were negatively associated with the average mean monthly minimum air temperatures in June-July. These rates were much higher in the highveld cities (varying from 63,9/100 000 to 71,4/100 000) than in the coastal cities (varying from 29,8/100 000 to 40,7/100 000). Age-specific MRs in the over-75-year age group in highveld cities were twice as high as the MRs of this age group in the coastal cities. Age-standardized MRs for chronic respiratory diseases, on the other hand, were not associated with winter air temperatures in these eight cities. Age-specific MRs for the over-75-year age group were also not related to the winter air temperatures in the eight cities. This lack of association between MRs for chronic respiratory diseases and winter air temperatures might be due to the confounding effect of air pollution.