What happens when you age?

In Germany, people between the ages of 60 and 75 are considered to be “of older age” or “elderly,” those between 75 and 90 are often described as “old,” and those between 90 and 100 are referred to as “very old.” People who are over 100 are called centenarians.

But the number of years you have lived is just one way to determine your age – which is then known as your chronological age. People of the same chronological age often haven't aged to the same extent, though. This can be explained by something known as your “biological age,” which is based on how healthy you are overall, as well as your physical and mental fitness.

Humans probably have a maximum lifespan of just over 120 years. But it is extremely rare for people to reach such an old age. In Germany, the average life expectancy is currently about 78 years for newborn boys and about 83 years for newborn girls. Statistically speaking, your life expectancy is a bit higher if you have already reached a certain age: For instance, a 60-year-old in Germany can expect to live to just under 82 if they're a man, and to about 85 if they’re a woman. It is not clear why women tend to live longer than men.

It is thought that the age you reach is partly determined by the genes you have inherited – in other words, by the DNA in your cells. Some people may only start becoming frail later, and live longer, as a result. But other factors have a positive impact too. These include living a healthy lifestyle with a lot of exercise and a balanced diet, being emotionally stable and having an intact social network.

Your body is made up of various types of tissue. Some consist of cells that don't live long so they constantly have to be replaced – such as skin cells. Over the years, these cells are replaced at a slower pace because fewer skin cells are able to divide. Some types of cells, such as nerve cells, live considerably longer. Other than previously believed, new nerve cells can still grow in adults with a healthy brain. In older age, though – or in people with dementia, for example – more cells die than can be replaced.

If not enough new cells are made, the affected organs can no longer function as well as they did before. Many organs also lose mass (get smaller or “thin out”) over the years. But because our organs have large reserves in order to cope with greater strain when necessary, this shrinking of reserves isn't noticeable for a long time. The typical signs of aging only appear once the reserves have become a lot smaller. These signs aren't medical problems, though, and it’s often possible to counteract them for a long time: For example, if muscles start becoming weaker, you can do exercises to strengthen them. Sports and exercise are considered to be good for you anyway – for instance, to keep your cardiovascular system (heart and blood vessels) fit and other organs healthy.

Some signs of aging can be seen from the outside: Your hair turns gray, and wrinkles and age spots appear on your skin. Our bodies are less able to store fluid in older age, so our spinal discs shrink and lose elasticity, for instance. As a result, people get smaller as they grow older.

When these kinds of changes happen in organs and tissues inside the body, they usually aren't noticeable for a long time. In some people they only become apparent under strain or in very old age. In others, this happens sooner.

As we grow older, it takes longer for signals to travel along our nerves, and our brains can't process information as well as they used to. This makes it harder to remember new things and react quickly. Our sensory organs gradually decline too. For instance, it's typical to develop age-related farsightedness in your mid-forties and hearing problems in older age. Your ability to smell and taste things can get worse over time too.

Growing older means having a wide range of experiences and going through changes – both mentally and physically. Throughout life, our body and mind adapt to external factors and events, including aging itself. This can happen subtly and subconsciously over a long period of time – for example, in the course of your working life or family life. Or it might happen more obviously and expectedly, like when training for a sporting goal or during rehabilitation after a serious illness.

People continue to change for as long as they live. Growing very old can be accompanied by loss and limitations, and the challenge of having to adapt to new circumstances again and again. But the aging process usually happens so slowly that this adaptation is constant and gradual. Because your family and friends grow older with you, you experience many of the changes together. When things start becoming more difficult, remaining physically active and drawing on your life experience and wisdom can help you to deal with a lot of the challenges you face.

Contentment and happiness are just as valuable in older age as they are in your younger years. A lot of elderly people enjoy their retirement, free of many previous pressures and constraints. Some look for new tasks, while others are happy to have more time for themselves, their loved ones and friends. The important thing is to stay active for as long as possible – both mentally and physically.