Dying in the 1990s vs. in the 2000s: Does Mental Functioning in Late Life Differ by Year of Death?

By Gizem Hülür, Humboldt-Universität zu Berlin

Think you are smarter than your grandparents? You could be right. It has been documented that individuals born in the more recent decades of the last century perform better on intelligence tests than those born in earlier decades. James Flynn first found that later generations scored 5 to 25 IQ points higher than earlier generations, a finding that was consistent across 14 industrialized nations. Since then, a myriad of studies have shown that, when examined over the same age ranges, thinking and mental processing abilities are stronger in later-born groups of individuals than earlier-born groups, for young and old participants alike. These improvements in mental ability may have resulted from advances in various domains, including schooling, nutrition, and medical technology. They seem to indicate that culture-based efforts have successfully improved the thinking and processing ability of people of all ages.

Our study group decided to approach these differences in thinking abilities between generations from a slightly different angle, namely, living conditions late in life. While most researchers examine individuals depending on birth year, we examined people by death year. In our study, we used data from now-deceased participants in the Asset and Health Dynamics Among the Oldest Old (AHEAD) study conducted in the United States. We compared the data of people who had died in the 1990s to the data of those who had died in the 2000s. Specifically, we compared the episodic memory of these groups through a simple test of the ability to recall something they had just heard. Participants were read a list of 10 words and were asked to recall as many words from the list as possible, immediately after they heard the list and about five minutes later. We calculated how many of the total words were correctly remembered and used this value to determine how memory changed as age increased. We anticipated certain factors that could affect our results, like gender, and used statistical methods to control for them.

Our results were very surprising: there were no trends favouring the later-dying group. At age 80 and at two years prior to death, people in the group dying in the 2000s performed even worse on the memory test than those dying in the 1990s. We also found that people in the later-dying group showed steeper memory decline than those in the earlier-dying group.

What could be the reasons for these odd results? The first is the idea that memory decline has intensified because of ‘manufactured survival’. It is possible that life has been and is being extended through medical and technological advances at the cost of functioning in later life. ‘Manufactured’ extension of life in the later-dying cohort may contribute to what looks like greater losses in mental faculties towards the end of life.

A second possible reason is that although medical advances have extended life further and further, the advances may not have helped people maintain the earlier levels of functioning in the years added to life. For example, although a walking stick is adequate to help an individual in his/her mid-70s walk, even a walking frame may not provide adequate walking for someone in his/her late 80s.

A third reason might be that because the length of life is being increased, more and more individuals are reaching older ages. So, later-born groups might show a wider variety of health problems than earlier-born groups, because of which the average memory at any given age may be low.

In conclusion, the findings seem to suggest that the improvements in mental ability previously reported across adulthood and old age are not generally applicable to the oldest old or to the last years of life. It is very important that we gain a better understanding of this trend, because it may guide political and social decisions aimed at improving the mental health of the fastest growing segment of the world’s population—the elderly.

More information can be obtained from Hülür, G., Infurna, F. J., Ram, N., & Gerstorf, D. (2013). Cohorts based on decade of death: “No evidence for secular trends favoring later cohorts in cognitive aging and terminal decline in the AHEAD study.” Psychology and Aging, 28, 115–127. doi: 10.1037/a0029965. Download available from http://www.psychologie.hu-berlin.de/mit_pub2?pid=1685131&i=11

 

Gizem Hülür¹, Frank J. Infurna², Nilam Ram³ & Denis Gerstorf^1,3
1 Humboldt-Universität zu Berlin, Berlin, Germany
² Arizona State University, Tempe, AZ, USA
³ Pennsylvania State University, PA, USA
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