Estimating excess winter mortality in Serbia

Seasonal variations in mortality are well documented, indicating a higher death rate during the winter compared with other periods of the year. Despite the evidence that vulnerability to winter weather has decreased, a significant number of preventable deaths still occur during the colder period of the year. Assessment of measures for excess winter mortality (EWM) is important for the public health system and what may be improved, but also for policymakers and stakeholders in order to be informed about current as well as future mortality-related climate change issues. This paper explores trends in EWM in Serbia and examines the validity of the methods of estimating EWM using monthly mortality data for the period 2000-2021. In order to estimate excess death using different measures, three methods were applied. First method (M1) uses the winter period as December to March and compare with the average of the non-winter period (preceding: August-November and following: April-July); second method (M2) defines winter as December to March against summer months (preceding: August and September, and following: June and July); and the third method (M3) set six months from October to March as a winter against the six-month non-winter period (preceding: August and September, and following: April to July). All three methods confirmed a higher number of deaths during the winter, and highest excess winter mortality was observed using the M2. This method determines winter as a four-month period from December to March, which is arbitrary but also well recognized in literature and generally used by public health services. The summer period in M2 is also casual and adjusted to the latitude. The main disadvantage of M2 refers to excluding April, May, October, and November from the winter/summer ratio. Compared with M2, M3 gives slightly lower excess winter mortality, but this measure classifies months in two too-wide seasons. The first measure, M1, estimates the lowest number of excess deaths, but considering climate characteristics in Serbia, this method uses the most suitable approach to assess winter mortality.