Ageing is the biggest killer worldwide, and also the largest source of morbidity. Ageing kills 100,000 people per day; more than twice the sum of all other causes of death. This equates to 37 million people – a population the size of Canada – dying per day of ageing. In developed countries, 9 out of 10 deaths are due to ageing. 

Ageing also accounts for more than 30% of all disability-adjusted life years lost (DALYs); more than any other single cause. Deaths due to ageing are not usually quick and painless, but preceded by 10-15 years of chronic illnesses such as cancer, type 2 diabetes and Alzheimer’s disease. Quality of life typically deteriorates in older age, and the highest rates of depression worldwide are among the elderly.

To give a relevant example of the effects of ageing, consider that ageing is primarily responsible for almost all COVID-19 deaths. This is observable in strong association of COVID-19 mortality with age (middle panel):

The death rate from COVID-19 increases exponentially with age (above, middle). This is not a coincidence – it is because biological ageing weakens the immune system and results in a much higher chance of death from COVID-19. The weakening immune system also results in greater senescent cell burden, and increased risk of cancer, to give just one example of how ageing is connected with chronic illness.

The mortality rate doubling time for COVID-19 is close to the all-cause mortality rate doubling time, suggesting that people who die of COVID-19 are really dying of ageing. Without ageing, COVID-19 would not be a global pandemic, since the death rate in individuals below 30 years old is extremely low.

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