Your genetic inheritance determines 50% of your life expectancy.

Adapted from BMJ 21-28 March 2026

Estimates of the genetic contribution to human lifespan have been surprisingly low and often show rates of 20% or less.

A re-analysis of Scandinavian twin cohort studies now puts this figure at 50%.

The reason for lower figures is that mortality rates are distorted by external causes that often have a familial effect such as infection, violence and other unintentional harms such as eg road traffic accidents or natural disasters or building collapses.

When these deaths are excluded the heritability of the intrinsic life span rises to around 50%.

This is similar to other complex traits such as body mass index, blood pressure and general cognitive ability.

My comments: Recently a friend who is adept at trawling ancestry sites discovered information about my family tree. There was a great deal of poverty and early death. I added up the ages of death of my parents and grandparents and divided the figure by six. According to this, my heritable life expectancy is 54.8 years. I’ve already lived 12 years longer than this. Here is a list of the ages and causes of death:

Women: Jeannie, my mother’s mother : Age 38 Lobular pneumonia and heart failure due to Pneumococcal Pneumonia – now has effective anti-biotics and vaccination. Ellen my mother: Age 46 Myocardial Infarction due to Ischaemic Heart Disease – now would have substantial chance of success after a stent operation and modern drugs. Sarah my father’s mother : Age 71 Heart Failure due to Pernicious Anaemia- now treatable with vitamin injections and drugs.

Men: Thomas, my father’s father: aged 29 Burns and Pneumonia due to Industrial Accident- chances of this very much reduced now with Health and Safety at Work Legislation. Robert, my mother’s father aged 66. Head injury due to fall from a height at work due to Industrial Accident – chances of this very much reduced due to Health and Safety at Work Legislation and practices around scaffolding. Tommy my father aged 79: Cardiac Failure due to Hypertension. Would still have died of this but modern drugs slow down the progression and he could possibly have added up to a further five years of life, though not without debility.