Another kind of birthday
There are two main ways to measure a person’s age. The first is the standard method, known as chronological age – the kind tracked by revolutions of the sun. But there is also your biological age, which indicates the rate at which you are ageing physically – the maturity of your organs and cells. It can vary wildly between different people and even within the same body.
As we rack up the years, it’s common wisdom that our chronological age will eventually catch up with our looks: skin becomes thinner and less even-toned, with lower elasticity, as the cells responsible for producing pigment and collagen die off or become “senescent” – meaning they stop renewing themselves and continue to exist in a kind of dormant state.
But it is the environment that tends to do the real damage. Though ultraviolet B (UVB) radiation can damage our DNA – leading to sunburn, mutations and skin cancer – 95% of the total UV radiation that makes it to the Earth’s surface is ultraviolet A (UVA). This portion of the sun’s rays has a longer wavelength, which allows it to penetrate deep into the dermis – where it breaks down collagen and stimulates cells to produce melanin.
At the microscopic level, photoaged skin – skin that has been aged by the sun – is thicker, with tangles of misshapen elastin and collagen fibres. At the visible level, it is often irregularly pigmented and significantly more wrinkled. This is true whether you have very light skin which is incapable of tanning, known as type one on the Fitzpatrick scale, or very dark skin, type six, which the scale inaccurately describes as never burning. Even deeply pigmented skin can burn and is susceptible to photoaging, though it will take longer for wrinkles to kick in.
In fact, it’s thought that intrinsic factors are responsible for the tiniest fraction of the classic “aged” look, while UV light is responsible for over 80% of visible skin changes. If you spent your whole life indoors with the curtains drawn, it’s possible that you might not see significant alterations to this organ until you reach your 80s.
Crucially though, along with these effects the skin also undergoes a chemical transformation. And it is this that might be having a profound impact on our overall health.
A chemical cocktail
In 2000, at the birth of a new century, a radical new concept emerged. By observing the way most organisms respond to stress, a group of scientists at the University of Bologna, Italy suggested a new way to think about ageing.
In a young, healthy person, the immune system is routinely deployed to maintain order – patching up damage and shooing off infections. But as we get older, or when we are in poor health, these inflammatory responses can pass a certain critical threshold – a point beyond which they go into overdrive, releasing a cascade of potent chemicals that rampage around the body, destroying healthy cells and mutilating our DNA. Enter “inflammaging” – the simmering backdrop of inflammation that accompanies the ageing process.
This is where the skin comes in. The latest research suggests that wrinkly, diseased, or damaged skin becomes part of this system of inflammation, releasing a chemical cocktail that leads to yet further damage and inflammation. “Chronologically aged skin exhibits higher expression levels of a whole panel of inflammatory cytokines and chemokines,” says Mao-Qiang Man, a research scientist at University of California San Francisco, who says that the same is also true for photoaged skin.
Locally, these chemicals degrade collagen and elastin, causing further skin thinning, wrinkles, and reduced elasticity, explains Tuba Musarrat Ansary, a postdoctoral researcher at Jichi Medical University, Japan. “They [also] disrupt the skin’s barrier, increasing water loss and susceptibility to stressors,” she says. The feedback loop is further compounded by senescent cells in the skin – either created by natural ageing or UV damage – which also release their own inflammatory chemicals.
But this is just the beginning. As the largest organ in the body, the skin can have a profound impact. The chemicals released by diseased and dysfunctional skin soon enter the bloodstream, where they wash around, damaging other tissues. Amid the ensuing systemic inflammation, chemicals from the skin can reach and harm organs that seem entirely unrelated, including your heart and brain.