In 1987 Laslett, a British historian, defined an “age” model of life. His last age was the Fourth Age.

In the First Age we are “young, learning, dependent and maturing”. The Second Age begins when we start work. It is when we become “independent, take responsibility for our own lives and for our families”. Laslett defines the start of the Third Age as “retirement” and “the culmination of life”. It is an era for “personal achievement and fulfilment”. His Fourth Age is characterized by “dependence, decrepitude, and death”. Some authors have extended these three D’s of the Fourth Age to four and included “depression”.

Clearly in his model there are no fixed dates to move from one age to the next. There are huge variations across individuals. The Fourth Age does not start on a particular birthday and is a point on a continuum. Today even retirement is no longer a fixed point. His model however does have advantages. It avoids dividing life based an arbitrary cut of chronological age. Such as sixty-five to seventy-five, seventy-five to eighty-five etc., does.

The model has proved remarkably durable. It uses events in life rather than age. Its echo can be found in modern issues of defining the end of “healthy ageing”.

A Modern Version of the Fourth Age

Governments have wrestled with how to define their version of the Fourth Age. Different approaches have evolved to define its start. Some have used hard medical diagnoses. How many chronic diseases does an individual have and how severe they are? Most governments have turned to individual’s perceptions of their own health. The end of “healthy ageing” is therefore in the mind of the individual. It depends on them and their environment.

In the UK the survey question is:

“ Do any of your conditions or illnesses reduce your ability to carry out day-to-day activities?’

The second question has three possible answers: Yes a lot/ yes a little/ not at all. The first two are combined and used as the definition of what is effectively the start of a Fourth Age.

The Postponement of Disability Onset.

The UK measures have been taken since the 1980’s. Since that time life expectancy has moved. In 1980 the most likely age for someone to die was 77. Forty years later that had risen to 87. The good news is that the onset of disability has moved with it. The chart below shows the improvement from 1981 to 2017.

The survey in 1981 measured what percentage of individuals had poor general health. It also measured the percentage reporting that they had a longstanding disability. The chart represents the difference between those numbers and the results from 2017. Across every age the percentage reporting poor general health were lower. At aged 73 they were 25% lower. Those reporting “Limiting Long Standing Disability” also declined at every age. In both cases the effect is most pronounced up to the age of 75.

Levels of poor general health for women aged 70 years in 2017 were around the same as for those aged 60 years in 1981. Levels of limiting longstanding illness were those of women aged around 64 years. For men, levels of poor general health at age 70 years in 2017 were around the same as for those aged 65 years in 1981. While levels of limiting longstanding illness were similar to those around 57 in 1981. In general women tend to have lower levels of perceived general health. Long term, disability inducing illnesses are about the same.

Remaining Life Expectancy (RLE)

The Fourth Age idea is reflected in the emergence of a new way of setting statutory retirement age. Instead of setting an arbitrary pensionable date it is based on life expectancy. In Denmark the age is set so that the average person will receive 14.5 years of pension. Effectively you receive pension for your fourth age, to cover the period when disability bites.

Researchers in Germany have used RLE as a health predictor. They showed that RLE is a better predictor than chronological age of the onset of many illnesses. This not for all illnesses. The majority however seem to be concentrated in the fourth age. That is irrespective of at what chronological age the fourth age starts. This is in line with the WHO definition of ageing as an incremental accumulation of deficits.