Why (and how) are we living longer — and what can we do about it?
Published: May 1, 2018
If death is a finish line, that line has continually moved farther and farther away over the past century. In fact, we’re not sure if we’re running a 10-kilometre race or an ultramarathon, or whether there’s an end to the race at all.
It’s this phenomenon – why and how we’re living longer – that internationally recognized biologist Tom Kirkwood explored in a recent lecture at McMaster.
Kirkwood, professor emeritus and the former Associate Dean for Ageing at Newcastle University’s Institute for Ageing as well as a Commander of the Order of the British Empire, is a member of the McMaster Institute for Research on Aging’s International Scientific Advisory Committee.
He, along with the other members of the committee – all global experts in aging across a variety of disciplines – visited McMaster recently to participate in a two-day meeting designed to explore both scientific and social issues surrounding aging. The committee members were brought to McMaster by MIRA and the Labarge Centre for Mobility in Aging to review the institute and centre’s progress and provide input into research programs and strategy.
In his talk, Kirkwood outlined what was driving up the average age of death – and whether there was, in fact, any evidence for a pre-determined limit on how old a human can get.
People are living longer. And as simple as that sounds, the issue is remarkably complex.
If you look at a graph depicting life expectancy in the world’s longest-lived countries – a list that includes Sweden, Norway, Japan and non-Maori New Zealanders, among others – you’ll see a striking 45-degree line tracing the increase in life expectancy from 45 years old in Sweden in 1840 to almost 85 in Japan in 2000.
This makes sense. Better public health measures introduced in the mid-nineteenth century, including cleaner drinking water, better sanitation and, latterly, widespread use of vaccines, began to decrease the number of deaths in early and middle life, leading to an increase in overall life expectancy through to the mid-twentieth century.
In 1980, the UN predicted the increase in lifespan would start to plateau, as improved public health became a less significant factor in determining how long someone would live. The general assumption was that human life was simply programmed to stop after a certain period; there was a ceiling for human existence, and we had just about hit it.
But contrary to expectations, life expectancy continued to increase.
The UN made that same prediction again in 1990. And still the number continued to rise – and continues to do so today.
That’s because increasing life expectancy numbers are now due to more people literally living longer and healthier lives, rather than a large number of deaths in early and middle years contributing to a lower overall average lifespan. Life expectancy is now influenced more by people living longer than people dying young.
Kirkwood pointed out that the nature of aging itself was changing, as older adults were reaching a more advanced age in better condition than generations before them. And because Kirkwood and others’ research has shown aging is due to a lifetime’s accumulation of molecular and cellular damage – rather than any biologically programmed human expiry date – it stands to reason that there is at least the possibility of extending life, perhaps significantly, by continuing to address that damage.
Of course, simply extending life is not enough, Kirkwood explained. A long health span – the period of time that a person remains free of significant disease or disability – is of primary importance as well. And, of course, health and aging go hand-in-hand; age is the biggest risk factor for a host of conditions, including cancer, heart disease, osteoporosis, diabetes and macular degeneration.
Extending the health span is complicated, because aging itself has such variable trajectories. While genetics is thought to account for about 25 per cent of how we age, other factors, including lifestyle, nutrition, socioeconomic status and environment, all play a role as well.
Researchers in aging at McMaster are working to better understand these varying paths through older age through institutes and centres like MIRA and the Canadian Longitudinal Study on Aging. The CLSA currently follows 50,000 Canadians between the ages of 45 and 85. Officially started in 2013, the study will follow participants until 2033 or until they die, and will collect information on the changing biological, medical, psychological, social, lifestyle and economic aspects of people’s lives.
“Our many research initiatives aim to develop the evidence that will help us understand the triggers that push us toward a healthy versus non-healthy trajectory, and the tools to help older adults live well for as long as possible,” says Parminder Raina, the study’s lead and scientific director of MIRA.
The interplay between those complex factors makes it difficult to predict how, exactly, science may contribute to the future of healthy aging. While research is ongoing, there’s still much to learn.
In other words, we’re in uncharted territory.
“What’s happening to longevity around the world is one of the biggest game changers on the planet as we go into 21st century. It was not foreseen that we’d be in the position that we’re in now. Lots of organizations are struggling to play catch-up.”
The McMaster Institute for Research on Aging (MIRA) aims to optimize the longevity of Canada’s aging population through research, education, and collaboration. Interdisciplinary teams work alongside older adults and key stakeholders to find ways that will help Canadians spend more years living well. MIRA also acts as an entry point to some of McMaster’s existing research platforms in aging, including the McMaster Optimal Aging Portal and the Labarge Centre for Mobility in Aging. The Labarge Centre, funded through a donation from McMaster Chancellor Suzanne Labarge, emphasizes mobility – a cornerstone of healthy aging. It seeks to better understand the range of health and social challenges associated with mobility in aging in order to optimize the well-being of Canadians and reduce related health and social costs. For more information, go to http://mira.mcmaster.ca/.