Climate and disease

Area of Science:

• Environmental Health
• Epidemiology
• Public Health

Background:

• Seasonal variations in mortality are well-documented for various causes, including respiratory and cardiovascular diseases, and diabetes.
• Mortality rates are generally higher in winter than in summer, with variations observed across different age groups.

Purpose of the Study:

• To analyze seasonal variations in mortality across different population groups in South Africa.
• To compare the impact of air temperature and pollution on mortality rates.
• To investigate geographical differences in seasonal mortality patterns.

Main Methods:

• Literature review on seasonal mortality variations.
• Analysis of mortality data for different ethnic groups in South Africa.
• Comparison of mortality rates in Durban and Johannesburg.

Main Results:

• White and Asian populations in South Africa exhibit typical winter-high, summer-low mortality patterns.
• Coloured and Black populations show a bimodal seasonal mortality pattern with peaks in both winter and summer.
• Infant mortality, primarily from gastro-enteritis in summer, contributes to the bimodal pattern in Coloured and Black populations.
• Seasonal variations in all-cause mortality are greater in Johannesburg than Durban, linked to higher respiratory disease mortality in Johannesburg.
• Air temperature is a stronger determinant of respiratory and cardiovascular deaths than air pollution, with a time lag of up to a week.

Conclusions:

• Seasonal mortality patterns differ significantly across South African ethnic groups, influenced by age structure and specific disease profiles.
• Air temperature, particularly prolonged periods of extreme heat or cold, is a key driver of seasonal mortality fluctuations.
• Geographical variations in climate and disease prevalence contribute to differing seasonal mortality patterns within the same ethnic group.