Materials and methods. For the study, data on the natural movement of the population during 1959-2018 were used. Standardized mortality rates were calculated using the direct standardization according to the world standard of age structure (WHO, 2000). Regression analysis was used for evaluating the studied parameters in dynamics. Segmented linear regression modeling and calculations of trends have been performed with the specialized software Joinpoint Regression Program.

Results. Six periods of changes in the population mortality rate non-affected by the age structure bias in the BSSR and the Republic of Belarus have been determined according to the developed model based on the evaluation of the annual SMR growth. During 1959-2018, there were 2 periods of SMR increase ((1964—1984, 1987—1994), 2 periods of SMR decrease (1959—1964, 2003—2018), and 2 periods when SMR did not change (1984—1987, 1994—2003). As a result of changing periods of increase, decrease and stabilization of population mortality, which took place within the frames of the study, in 2018, the population SMR “returned” to the 1970 level.

Conclusion. Six periods with different trends in SMR of the population of the BSSR and the Republic of Belarus for
60 years since 1959 till 2018 have been identified. The evaluation of the trends of age-adjusted mortality rate provides a basis for concluding that the periods of the model correspond to significant socio-economic effects, the development of healthcare and medical science in the second half of the ХХ — first quarter of the ХХI century: decreased SMR in 1959—1964, stabilized SMR in 1984—1987, quick increase in 1987—1994, and decrease of SMR since 2003. When excluding the influence of the population aging on the mortality indicators, the population mortality rate in 2018 is comparable to that of 1970.