Longer Life Expectancy Comes With Good Cognitive Health

December 10, 2015

The increased years of life expectancy being seen over the last two decades are generally spent in relatively good cognitive health, new findings from the United Kingdom (UK) suggest.

The research, published online in The Lancet on December 8, was conducted by a team led by Carol Jagger, PhD, Institute of Health and Society, Newcastle University, UK.

"Our data shows that we are living longer and a lot of that extra time is in good cognitive health," she commented to Medscape Medical News. "We tend to have better minds than we used to 20 years ago at the same age but not necessarily healthier bodies."

The researcher compared data from two identical studies (the Cognitive Function and Ageing Studies I and II) conducted in 1991 and 2011, which interviewed people aged 65 years or older in three geographically defined centers in England.

Prevalence estimates for three health measures — self-perceived health, cognitive impairment, and disability in activities of daily living — were combined with mortality data to produce health expectancies for the three regions together.

"More Good News than Bad"

"The data show that life expectancy has increased in the past 20 years, and that the additional years are not associated with significant cognitive decline. In contrast, they are affected by disability, although this is mainly mild disability," Professor Jagger said. "So we are reporting good news for our minds but not such good news for our bodies. But I would say this is more good news than bad."

Self-rated health was also good, with most of the extra years of life rated as good, very good, or excellent. However, Professor Jagger noted that self-rated health is difficult to assess because it is so subjective and people's expectations change as they age.

"I would say that although there was an increase in mild disability, this does not seem to cause people to say they are in bad health. Old people are quite stoical. They look around and see that many of the peers have died so a bit of mild disability doesn't seem so bad."

She explained the prevalence of cognitive impairment is increasing with the aging of the population "because more people are reaching very old age we are of course seeing more cognitive impairment," but actually these data show that cognitive impairment is less likely at any specific age than it used to be.

In the study, the average age of developing cognitive impairment was delayed by 4 years for women over the 20-year period. "In 1991, a woman of 65 would spend an average of 60% of her remaining life free of cognitive impairment whereas in by 2011 that figure had risen to 71%," Professor Jagger reported.

The data show that the number of years living with severe cognitive impairment has also reduced a little for women but not men. The 2011 figures suggest that on average about 10 months of a woman's life will be spent with severe cognitive impairment compared to about 1 year in the 1991 data.

"But this has to be balanced against the increase in mild disability. We need to look more into what specifically this mild disability entails. We don't have good data on this yet."

Different Results for Men vs Women

For men, the cognitive impairment results have hardly changed over the 20-year period and show that men live with severe cognitive impairment for an average of 5 months, which was the same in 1991 and 2011, Professor Jagger said.

She speculated that men may spend less time in severe cognitive impairment because they are less likely to achieve very old age. "Men don't have the same staying power as women. Even at the same age women have more disability than men but they live through it, whereas men tend to die earlier. Women are more likely to live with arthritis while men are more likely to get fatal disease, such as heart attacks."

In the three regions combined, 7635 people participated in the 1991 study and 7796, in the 2011 study. They were assessed for self-perceived health (defined as excellent–good, fair, or poor), cognitive impairment (defined as moderate–severe, mild, or none, as assessed by Mini-Mental State Examination score), and disability in activities of daily living (defined as none, mild, or moderate–severe).

In the three regions combined between 1991 and 2011, life expectancy rose by 4.5 years for men and 3.6 years for women at age 65 years and by 3.0 years for men and 2.5 years for women at age 70 years.

Men gained an average of 4.2 years free of cognitive impairment vs 4.4 years for women. Gains were also identified in years in excellent or good self-perceived health: 3.8 years for men and 3.1 years for women. Gains in disability-free years were much smaller: 0.5 years for women and 2.6 years for men, mostly because of increased mild disability.

The researchers say their findings have important implications for government, employers, and individuals, specifically for raising of the state pension age in the UK and extension of working life, and for community care services and family carers who predominantly support people with mild to moderate disability to enable them to continue living independently.

In an accompanying editorial, Kenneth Rockwood, Dalhousie University, Halifax, Nova Scotia, Canada, comments that "the longing for longevity without decrepitude" has been a wish since ancient times.

While Professor Jagger and colleagues have documented important gains in health expectancies, he adds that these data "do not support complacency in public policy," Dr Rockwood writes. "Even so, it seems that living the unenfeebled old age promised to Odysseus will still somehow need special favour."

The study was funded by the UK Medical Research Council. Professor Jagger has disclosed no relevant financial relationships. Dr Rockwood is the founder and a director of DGI Clinical, has consulted for Roche, and has received fees for speaking from Nutricia.

Lancet. Published online December 8, 2015. Abstract Editorial

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