Gompertz Law Predicts Mortality in a Modern Cohort Study - The Manitoba Follow Up Study

Introduction: Gompertz Law, published in 1825, states that the age-specific force of mortality increases exponentially with age. This has implications for ageing people and ageing populations. We sought to determine if Gompertz Law of Mortality is accurate in a contemporary cohort study. 

Method: We analyzed data from the Manitoba Follow Up Study – a closed prospective cohort study of men who qualified for air crew training in the Royal Canadian Air Force during the Second World War. The cohort was sealed in 1948 when 3983 men with a mean age of 31 years old were enrolled. The date of death up to December 2025 was determined. We used Gompertz’s original equation and constructed a log-linear regression model of the natural logarithm of the incidence rate of death by age. 

Results: There were 3972 men whose date of death was known, 6 men who had not died, and 5 men for whom the date of death was unknown; with 180 230 person years of follow up. The incidence of death rose exponentially from the age of 25 to the age of 105, doubling approximately every 9 years. The log-linear regression model had a very close fit with the data. 

Conclusion: In a closed cohort study, Gompertz Law of Mortality appears to be accurate. This exponentially increase in death rate should be taken into consideration when planning individual and population health decisions, and in prognostic models.