The idea that life expectancy is going to keep increasing is flawed. We certainly won't get to an average of 100
There is a widely held assumption that our life expectancy is going to keep increasing. This belief is so ingrained that when the former treasurer announced last year that we’d all be living to 100 by mid century, no-one even batted an eyelid.
It is quite an extraordinary assumption too, as it is not based on science, but merely an extrapolation of recent trends.
In contrast, we actually have a good understanding of how and why our lifespans have increased over the last two centuries. The dominant reason is not modern health services, but public health measures introduced in the 19th and early 20th century; chlorinated water and sanitation, healthier and safer foods, immunisation, family planning, as well as antibiotics and infection control.
These measures greatly reduced infant and childhood mortality, which in turn have a disproportionate influence on life expectancy compared to extending the lives of older adults.
This is important to remember, as discussion about “health” nearly always centres on hospital beds, pharmaceuticals and hi-tech procedures, all of which may improve health outcomes but make only a modest contribution to longevity.
If we are really to maximise health outcomes, and if the past is anything to go by, then it will be through population-based approaches, such as addressing social and environmental factors rather than a focus on individualised treatments.
So what might we realistically expect?
If all goes well, and if the future is like the past, we would at best see small diminishing gains until we plateau at our maximum possible lifespan, whatever that maybe. There’s little reason to think the average will be anywhere near 100 years.
But that’s an unlikely scenario. Right now, there are a number ‘grey rhinos’ – large, dangerous and heading straight for us – any of which may impact on both our lifespans and healthspans.
Firstly, our triumph over infectious diseases is in jeopardy as antimicrobial resistance increases. Without new classes of antibiotics, we are likely to see the re-emergence of infections once banished from the developed world, such as TB.
And anti-microbial resistance has another sinister consequence – to derail our healthcare system altogether. Without reliable treatments for common infections, elective surgery, invasive investigations and chemotherapy become very risky.
As well, we are now seeing an unfolding epidemic of non-communicable diseases as the result of sedentary, inactive lifestyles and poor nutrition. Increasing rates and earlier onset of diabetes, obesity, hypertension, osteoporosis, vascular disease and their complications, as well as dementia and some forms of cancer, that will overstretch our health services and worsen health outcomes.
Both antimicrobial resistance and escalating non-communicable diseases are potentially solvable problems. But we are not even headed in the right direction. There are no large-scale projects to find new antimicrobial drugs, and no meaningful curbing of overuse. Neither are we reshaping our cities, employment or transport infrastructure to facilitate more active, healthier lives.
Climate change has been identified as the “greatest threat to our health this century”. It already resulted in more frequent and severe extreme weather events, heat waves and droughts, which have direct health impacts. It also has insidious and far-reaching impacts from changes in food and freshwater quality and security.
Many infectious diseases are “climate sensitive”, due to higher pathogen multiplication rates and longer survival in warmer and more humid weather, also from changes in the range and populations of disease vectors like mosquitoes and snails, and other animal hosts. We are already seeing the spread of diseases in humans, livestock and agricultural crops affecting populations without previous exposure or immunity.
Rates of species extinction have quite recently increased by 100 to 1000 times, largely due to land clearing, overfishing, pollution, and increasingly climate disruption. Diminishing biodiversity and compromised ecosystems are undermining the essential natural services on which our health and ultimately survival depend.
Recently, Harvard academics warned that we need to spend billions of dollars to prevent and manage global health crises. Outbreaks of disease such as Ebola and Zika are becoming increasingly likely due to growing population, globalisation and environmental degradation.
In contrast to the early to mid 20th century, the last three to four decades have seen a reversal of the trend toward increasing equality. Yet the evidence suggests fairer societies result in healthier and longer lives, and not just for those at the bottom, but for everyone within that society.
There are, of course, many other factors, such as financial instability and resource depletion, which can also directly affect our health or undermine the determinants of our health.
The long and short of it is that while we may not be able to accurately predict the future, it would be foolish to think things will keep getting better, because of past trends, especially when there are very foreseeable and expected surprises.
Dr George Crisp is a Perth GP and WA Chair of Doctors for the Environment Australia
