In previous Newsletters I have introduced various studies of perceived age. When someone is perceived to be old depends on the age of the person you ask. A large group of Europeans under 30 said that “old” starts at 60. Only five percent of a group of 60 year olds would agree! (Newsletter #004 Twenty Five Years Too Early”). When asked how old do you feel we all say we feel younger than our chronological age. At least if we are over 40. Usually there is a twenty percent difference. I have been looking for more objective measures.

The Chances of Death Approach.

I was listening to a presentation by Prof Jane Falkingham. She heads the ESRC Centre for Population Change in the UK. She had a definition of “old” based on the probability of ones death. In 1951 a fifty year old man had a 1% chance of death. She defined that as “old”. A 75 year old had a 10% chance of death, according to the UK Government Mortality Tables. She defined that as “very old”. For a woman the 1% chance occurred at 56 and the 10% chance at 78. Using those simple definitions she could show the extension of healthy living. By 2021 the 1% level had risen to 65 from 50 for men. The 10% level rose to 87. For a woman the 1% level had risen to 69 and the 10% chance to 88.

Laura Carstensen developed the Socioemotional Selectivity Theory. It argues that we become increasingly aware of our own mortality. This does not coincide with chronological ageing and is specific to an individual. It changes our motivation. We become more focused on our own happiness. We avoid potentially distressing situations. Is Prof Falkingham’s probability of death model linked?

Biological Age: The Health Deficit Index.

All humans age chronologically by a year each year. Biological age is individually specific. Biological ageing is:

“ the accumulation of damage to cells and tissues in the body and the resultant gradual deterioration in bodily functions.”

To assess how “old” someone is we must look at those deteriorations or deficits. We have lots of measures. We can look at behavioural measures such as “needs help bathing” or “not being able to get in or out of a chair”. We can have self-reported measures of heath or mental state. We can have medical measures such as blood pressure or BMI. We can also use diagnoses of chronic diseases such as cancer.

To assess biological age we would look at the percentage of all possible deficits someone had already accumulated. It is not an individual deficit that is the problem. The accumulation of deficits is a complex system. The presence of deficits is cumulative and progressive. As you accumulate deficits the chances of more occurring increases.

The Frailty Index was mentioned in a previous Newsletter (Newsletter #093 Healthier Ageing”). Researchers have combined these deficit measures into a single health deficit index. They have found that it does not matter what measures we use, as long as we use enough of them. Above about thirty different measures, the index becomes robust. This rather surprising idea can be explained by thinking about the underlying processes. It turns out that if you have enough measures in the index it captures that complexity. If you miss out a deficit its impact is carried by other measures. To test this researchers have systematically dropped measures out of the index and redone their analyses. The results come out the same,

How Fast Are We Ageing?

There have now been over 100 studies using the Frailty Index. The results are interesting. An individual’s index score is a better predictor than chronological age for many life events. It can better predict the likelihood of being institutionalized in a care home. It can better predict better whether someone will claim on disability insurance. It is a much more powerful predictor of death. Adding chronological age to the prediction does nothing to improve the accuracy. The information in chronological age is subsumed into the index.

The many studies show the increase in frailty with age is an upward curved slope. This represents the cumulative and progressive nature of deficits. The curve has a maximum around 60%. This seems to represent the most deficits we can withstand. The frailty index in exponential and increases by a fixed percentage each year.

Americans appear to be accumulating deficits at close to 5% per year. Canadians are at about 4.5%. A study of 14 European countries gave an average of 2.5%. There were little differences across Europe. These averages hide variability within. Caucasian Americans are accumulating deficits at the same rate as the Europeans. Women tend to accumulate deficits at a slower rate than men. Economically deprived regions accumulate deficits faster. Of course the problem is that these different groups may start at different level of deficits. There may be different start points and different accumulation rates but end point is the same! Most studies forecast an expected age of between 95 and 105 even today.