YOU ARE GOING TO DIE. Not a very cheerful prospect. But remember, science does not shirk from any topic. Every year, around 30,000 people die in Ireland.

This keeps the undertakers busy. They see a lot of dead people. Some die ahead of their natural lifespan because of an accident. Some make it to a ripe old age. We fill our lives with a busy schedule, but if you look at the calendar on your smartphone there will
definitely be a date in the future on which you will die.

Go on, scroll down through the dates into the future … you will pass a date on which you are going to die. The Grim Reaper just hasn’t filled that date in yet. 

What’s interesting is that a child born in Ireland today can reasonably expect to live to be over 100. This is because of advances in modern medicine, with medicines like statins (which keep cholesterol in check in our bloodstream and therefore decrease the risk of heart attack), and hopefully better lifestyles (not smoking, eating less, exercising more and getting plenty of sleep) improving lifespan for all.

However, around 20% of people will die in a sudden or unexpected way – an accident or a stroke, perhaps. A further 20% will die of cancer (although those numbers will improve, with new treatments continuing to emerge).

Those with cancer will stay relatively healthy until quite close to death, when there is usually a linear deterioration over a few weeks. The rest of us will undergo a slow deterioration as we age, suffering from various chronic medical problems such as heart or kidney failure, or dementia, buoyed by a range of medicines to keep us going longer.

By some estimates, more than 90% of the medicines you will take will be taken in your last year of life.

Your final months will be characterised by a series of relapses and remissions against a backdrop of slow deterioration in physical function. Pretty grim, huh? So eat, drink and be merry, for tomorrow (or whenever) we die. 

How to diagnose death

One thing about death that has preoccupied people for hundreds of years is how we actually know someone is dead. It may seem obvious now, but in the past it wasn’t (unless of course someone had their head chopped off). 

Say you lived a few hundred years ago and old Grandpa (who back then was probably 40 years of age) seemed to have croaked. You didn’t call for a doctor, you called for the priest, who would make the determination of death. All the priest would have at his (never her) disposal would be outward signs of death.

They might hold a mirror over Grandpa’s mouth to see if it clouded over. Or a feather under his nose to see if it moved. In the 1700s enough was known about the human body to check for his heartbeat. The stethoscope, though, wasn’t invented until 1816 by the French physician René Laennec.

The binaural stethoscope (on which modern stethoscopes are based) was invented by Irish physician Arthur Leared. There was a rather gruesome procedure known as Balfour’s test, where long thin needles were stuck into a person’s heart and then left protruding with small flags attached. If the flags moved, the heart was beating and the person was deemed to be alive.

However, doctors began to realise that, although outwardly the person appeared to be dead (with no detectable heartbeat or breathing), they might in fact be still alive and perhaps might recover. This phenomenon led to people being buried alive, which wasn’t especially unusual in the 19th century.

Edgar Allan Poe (who according to John Lennon often got a kicking) made great mileage from such horror stories. To provide a safeguard, some coffins had a string from the inside up to the ground attached to a bell, which the unfortunate person could ring should they awake in their coffin – a dead (or actually live) ringer.

Even today, doctors are cautious when pronouncing people dead under certain circumstances. When a patient is brought to a hospital comatose from, for example, attempted suicide or drowning, they may well have no signs of life. Their bodies, which will be cold to the touch, are usually warmed up first to check that they are actually dead, as signs of life might well return. 

The term ‘warm and dead’ is used for these unfortunate people. Nowadays there are all kinds of ways to attempt to resuscitate someone, or keep them alive. A person can be hooked up to a ventilator, to maintain breathing and to keep blood circulating. There are a whole host of devices that can keep a person alive if you just measure their pulse as the indicator of being alive.

But in the 1950s doctors recognised that people were being kept ‘alive’ by machines. The phrases ‘persistent vegetative state’ and ‘irreversible coma’ were invented to describe these people. They weren’t coming back, because of brain damage that couldn’t be repaired. We therefore now define death as being ‘brain dead’.

A person who meets this whole-brain definition of death has lost the ability to breathe on their own. Breathing is essential to providing the oxygen your body needs to burn fuel in order to provide the necessary energy to keep the lights on. Simply put, dying starts when the body doesn’t get enough oxygen to survive. Different cells in your body die at different speeds, however.

If you cut yourself and your blood spills on the floor, that blood is full of white blood cells, which will continue to live for a few hours outside your body. The length of the dying process actually depends on which cells are deprived of oxygen.

The power of oxygen

The brain is especially greedy in this regard. It needs a lot of fuel to keep running. All those neurons crackling away burn 75% of the glucose you consume, and need oxygen to do it. Any cut-off in oxygen to the brain (as happens in a massive stroke, which blocks the main blood vessel in the brain – the middle cerebral artery) will kill you within three to seven minutes.

Cyanide kills in a similarly rapid fashion, because it directly interferes with the process of respiration (where oxygen is used to burn fuel to make the energy currency of cells – ATP). Similarly, if you cut off the blood supply to the heart by blocking, say, the main coronary artery, death will happen relatively quickly, as the heart goes into spasm.

For most, though, these sudden deaths won’t be the way you die. Your body’s systems will simply break down with time, as we saw in the chapter on ageing. Like all machines, the component parts simply wear out. As death approaches, there will be some outward signs that these systems are slowly failing, and that the Grim Reaper is knocking on the door (or the banshee howling up on the roof).

The person will sleep more to conserve whatever energy they have left, a bit like sleep mode on your computer. When energy reserves are very low, you won’t have the energy to eat and drink. Swallowing will become difficult and your mouth will become very dry. Any pain you might feel can usually be managed by a doctor.

Many people in fact shuffle off this mortal coil blissed out on a morphine-type sedative, falling almost literally into the arms of Morpheus. Not a bad way to go.

Humanology by immunologist Luke O’Neill is published by Gill Books. It’s nominated in the TheJournal.ie-sponsored Best Irish Published Book category in the An Post Irish Book Awards this year. The awards will take place on Tuesday 27 November – for more information and to look at all of the nominees, have a look at the website.