Tick, tock… how stress speeds up your chromosomes’ ageing clock



At a molecular level, stresses and strains can make your body clock break into a sprint.
Lightspring/Shutterstock

Szymek Drobniak, UNSW

Ageing is an inevitability for all living organisms, and although we still don’t know exactly why our bodies gradually grow ever more decrepit, we are starting to grasp how it happens.

Our new research, published in Ecology Letters, pinpoints factors that influence one of the most important aspects of the ageing process, at the fundamental level of our DNA. It suggests how stress can cause the biochemical body clock built into our chromosomes to tick faster.




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DNA – the genetic material in our cells – does not float freely in cells’ nuclei, but is organised into clumps called chromosomes. When a cell divides and produces a replica of itself, it has to make a copy of its DNA, and because of the way this process works, a tiny portion is always lost at one end of each DNA molecule.

To protect vital portions of DNA from being lost in the process, the ends of chromosomes are capped with special sequences called telomeres. These are gradually whittled away during successive cell divisions.

Telomeres (highlighted in white) are like molecular buffers for your chromosomes.
US Dept of Energy Human Genome Program

This gradual loss of telomeres acts like a cellular clock: with each replication they get shorter, and at a certain point they become too short, forcing the cell into a programmed death process. The key question is what this process, which plays out on a cellular level, actually means for our mortality. Does the fate of individual cells really matter so much? Does the ticking telomere clock really count down the remaining time our bodies have to live?

Cellular ageing is just one of many components of ageing – but it’s one of the most important. Gradual deterioration of our body’s tissues, and the irreversible death of our cells, are responsible for the most conspicuous effects of ageing such as loss of physical fitness, deterioration of connective tissues leading to skin wrinkles, or neurodegenerative diseases such as Parkinson’s disease.

What makes us tick?

Another crucial question is: are there factors that speed up or slow down the loss of our ticking telomeres?

So far, our answers to this question have been incomplete. Studies have provided glimpses of possible mechanisms, suggesting that things like infections or even dedicating extra energy to reproduction might accelerate telomere shortening and speed up cellular ageing.

This evidence is piecemeal, but these factors all seem to have one thing in common: they cause “physiological stress”. Broadly speaking, our cells are stressed when their biochemical processes are disrupted, either by a lack of resources or for some other reason. If cells lose too much water, for example, we might say they are in “dehydration stress”.

More familiar types of stress also count. Tiredness and overwork put us under chronic stress, as does feeling anxious for prolonged periods. Lack of sleep or emotional stress can alter internal cellular pathways, including telomere functioning.

With this in mind, we asked ourselves one simple question. Can various types of stress experienced by an individual actually accelerate their rate of ageing?

Stress and strain

In our research, led by my colleague Marion Chatelain of the University of Warsaw (currently University of Innsbruck), we chose to look at this question as broadly as possible. Many studies have looked at this problem in specific species, such as mice, rats, and various fish and bird species (both wild and in the lab). We compiled the available evidence into a summary of the existing knowledge, across all vertebrate organisms studied so far.

The emerging picture clearly suggests that telomere loss is profoundly impacted by stress. All else being equal, stress does indeed hasten telomere loss and accelerate the internal cellular clock.

Importantly, the type of stress matters: by far the strongest negative impact is caused by pathogen infections, competition for resources, and intensive investment in reproduction.

Other stressors, such as poor diet, human disturbance or urban living, also hastened cellular ageing, although to a lesser extent.

Getting radical

A natural question arises: what makes stress exert such a powerful influence on cellular clocks? Is there a single mechanism, or many? Our analysis may have identified one possible candidate: “oxidative stress”.

When cells are stressed, this often manifests itself through an accumulation of oxidising molecules, such as free radicals. Residing at the exposed ends of our chromosomes, telomeres are perfect targets for attack by these chemically reactive molecules.

Our analysis suggests that, regardless of the type of stress experienced, this oxidative stress might be the actual biochemical process that links stress and telomere loss. As to whether this means that we should eat more antioxidants to guard our telomeres, this certainly requires more research.




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I know what you’re wondering: does this mean we have discovered the secret of ageing? Can we use this knowledge to slow the ageing process or stop it in its tracks? The short answer is: no.

Ageing is too fundamental to our biology to get rid of it completely. But our study does underline an important truth: by reducing stress, we can do our bodies a big favour.

In the modern world, it is hard to escape stress completely, but we can make everyday decisions to reduce it. Get enough sleep, drink enough water, eat healthily and don’t push yourself too hard. It won’t buy you eternal life, but it should keep your cells ticking along nicely.


The author thanks his colleagues Marion Chatelain and Marta Szulkin for their contributions to this article and the research on which it is based.The Conversation

Szymek Drobniak, DECRA Fellow, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Migration helps balance our ageing population – we don’t need a moratorium



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Cutting immigration to Australia will impact the country’s demographic composition, with consequences for the working age population and income tax base.
Andrew Seaman/Unsplash

Liz Allen, Australian National University

Australia’s population is set to reach 25 million in the coming weeks. This is much earlier than expected. Eighteen years ago, projections estimated Australia’s population wouldn’t get to 25 million until 2041.

Western Australian Liberal Senator Dean Smith last week proposed a moratorium on immigration to give Australia some time to “breathe” and take stock. Claiming concerns over planning and infrastructure failing to meet population needs, Smith signalled Australia was unprepared, having relied on inaccurate population projections.

Immigration is often targeted when population levels seem out of control. But will a moratorium give Australia the supposed breathing space it needs?




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Migration impacts

Concerns about immigration and a perceived population crisis have crossed over the spectrum of Australian politics. One Nation’s Pauline Hanson has called for a plebiscite on immigration, while Labor leader Bill Shorten has raised concerns about the number of temporary migrants in Australia.

Immigration Minister Peter Dutton has said a cut to immigration numbers would have economic benefits, contradicting Treasurer Scott Morrison. And Smith’s idea to halt immigration to allow the nation’s infrastructure time to catch up with population demand is shared by prominent public figures, including Bob Carr and Dick Smith.

Australia’s population is ageing, which has potential adverse consequences for the future as proportionally more people exit the workforce, increasing reliance on a shrinking income taxpayer base. Immigration has the potential to offset these consequences of population ageing by contributing to the workforce and to government funds for essential services. Migrants also contribute to Australia’s future population by having children.

The latest available research suggests immigration levels at “about 160,000 and 210,000 seem to have the ‘best’ impact by 2050 on ageing of the population and the rate of growth of GDP per capita”.




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Current ABS projections provide an opportunity to examine what Australia’s demographic composition could look like if net overseas migration was zero, 200,000 (low), 240,000 (middle) or 280,000 (high) per year.

Based on 2011 census data, and medium-range assumptions for fertility and life expectancy, the 2013 (medium range) projections are tracking well with current estimates. These projections provide an indication of the impact of migration, measured as net overseas migration. Net overseas migration reflects the balance of incoming and outgoing movements and includes both permanent and temporary migration.

The four ABS scenarios show varying population numbers over the medium to long term. The higher the net overseas migration level, the bigger the population over the projected years. Interestingly, though, while zero net overseas migration would result in a reduction in population by the year 2070, the population would still continue to grow in the medium term due to natural increase (births minus deaths).


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Population composition is an important indicator to consider, rather than size alone. Age distribution is essential to understanding the fiscal opportunities and challenges a population faces.

Comparing the four net overseas migration scenarios illustrates the important contribution migration makes to Australia. The so-called dependency burden – the ratio of the number of children (0-14
years old) and older people (65 years or over) to the working-age population (15-64 years old) – is higher for zero and low net migration levels.

The current rate of net migration provides the middle ground in balancing population age structure and growth.


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Population projections

Planners need to know expected population size and growth to ensure adequate services and provisions. The ABS has produced projections for national and sub-national populations since 1950.

Population inquiries throughout Australia’s history have consistently called on such statistics to enable the country’s responsiveness and preparedness to accommodate numbers. Australia hasn’t set any population targets, mainly to avoid coercive population measures (such as mandating birth rates) and to allow flexibility in government policy, particularly around immigration intake.




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Estimating population size and growth into the future is about what might be (projection) and not what will be (forecast). So population projections are not predictions; they’re calculations of potential future populations based on assumptions about possible births, deaths and migration.

The “best-before-date” for population projections is considered to be around 5-10 years from the initial base year of calculation. This is why projections should be regularly updated based on best available population data (the census and vital statistics) to ensure assumptions reflect births, deaths and migration trends.

Australia is one part of the global community. Cutting immigration to Australia will impact the demographic composition of the country, with consequences for the working-age population and income tax base.

Any changes to the migration program should be considered alongside evidence. Available evidence shows Australia’s current migration program intake (190,000) is about right for Australia.

The ConversationAustralia doesn’t need a moratorium. What we need is a respectful, open and evidence-based population discussion.

Liz Allen, Demographer, ANU Centre for Social Research and Methods, Australian National University

This article was originally published on The Conversation. Read the original article.