By Ajay K. Singh, MBBS, FRCP, MBA
December 19, 2016
An article on December 16 in the Washington Post about the relationship between risky behavior, age, and grey matter caught my eye.
The theoretical construct behind this body of research is as follows: with healthy aging, there is progressive loss in grey matter volume in the right posterior parietal cortex (rPPC). The less grey matter in the rPPC, the greater aversion there is to taking risk.
Several metanalyses support a relationship between aging and less risk behavior (Mata R, et al, Ann. N. Y. Acad. Sci. 2011; Mata R, et al Psychol. Sci., Best R., Psychol. Aging 2015). Yale investigators Michael Grubb and colleagues in Nature Communication, tease out the relationships between age and grey matter volume with aversion to risk.
Grubb et al designed an experiment where he asked 52 adults age 18 to 88 years old to participate in a game that required them to make a binary choice of either choosing a guaranteed monetary gain ($5) or participating in a lottery where there was a risk of losing or the opportunity of winning between $5 and $120. All choices were made while the subjects were in an MRI scanner.
The Yale investigators observed that risk tolerance decreased monotonically within the 18-88 year age range. Analysis of the data using regression models demonstrated an independent relationship between rPPC and risk tolerance that did not change when controlling for age or gender.
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The conclusion of the experiment was that grey matter volume, rather than chronological age per se, determined aversion to risk. They state: ” Though both older age and decreased rPPC GMV are associated with risk tolerance, when the independent contributions of these factors are assessed, rPPC GMV still accounts for changes in risk tolerance, whereas age does not. These results refine and extend our existing understanding of the relationship between aging and risk tolerance by attributing behavioral changes to an age-related process (that is, changes in grey matter thickness) rather than to chronological age itself.”
This research confirms something that we’ve all appreciated for many years. Younger people tend to take more risk, and this willingness to tolerate risk attenuates with age. Grubb and colleagues provide some neuroanatomical proof to back this up.
Dr. Ajay K. Singh is the Senior Associate Dean for Global and Continuing Education and Director, Master in Medical Sciences in Clinical Investigation (MMSCI) Program at Harvard Medical School. He is also Director, Continuing Medical Education, Department of Medicine and Renal Division at Brigham and Women’s Hospital in Boston.