# The Strehler-Mildvan correlation as a valuable tool for monitoring the long-term health status of a population

## TL;DR

The Strehler-Mildvan correlation helps track population health over time, showing how mortality trends return to normal after major disruptions like wars.

## Contribution

Demonstrates the SM correlation's utility in analyzing long-term population health and its resilience after short-term shocks.

## Key findings

- Sweden showed the best agreement with the SM correlation model over time.
- Short-term events like World War I can disrupt the SM correlation, but populations tend to return to equilibrium.
- France exhibited the weakest adherence to the SM correlation compared to Sweden and the Netherlands.

## Abstract

The increase in the logarithm of mortality with age from 40 years onward can be described by a Gompertz linear relationship with two parameters. The long-term relationship between these two parameters can itself be described by another linear relationship known as the Strehler–Mildvan (SM) correlation. Long-term data from three countries were evaluated in the context of the SM correlation. The earliest available periods were 1751–1754 for Sweden, 1816–1819 for France, and 1850–1854 for the Netherlands, while the most recent periods were 2020–2021 for France and the Netherlands, and 2020–2023 for Sweden. The best agreement with the SM model was observed in Sweden, and the weakest in France. While the SM correlation model generally describes long-term trends well, it can be significantly disrupted over shorter calendar periods. If we view the population as a dynamic system, then large short-term shocks—such as World War I—can temporarily break the SM correlation. Over time, however, the system tends to return to an equilibrium state in which the SM model becomes applicable again.