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By: Ria Shah
Correlations between tests of aging in Hiroshima subjects--an attempt to define "physiologic age".
Hollingsworth, J. W., et al. “Correlations between Tests of Aging in Hiroshima Subjects--an Attempt to Define “Physiologic Age”.” The Yale Journal of Biology and Medicine, vol. 38, no. 1, 1 Aug. 1965, pp. 11–26, www.ncbi.nlm.nih.gov/pmc/articles/PMC2591119/?page=16. Accessed 7 June 2024.
Background:
Scientists still don’t know why radiation causes premature death. Experiments have been done that show irradiated animals die faster than normal ones even after excluding deaths caused by cancer. It is also theorised that ageing is an accumulation of somatic mutations (alterations in the DNA that occur after conception), and radiation would increase the likelihood of somatic mutations therefore increasing the rate of ageing.
Study:
The study was performed on 437 survivors of Hiroshima and Nagasaki. The aim was to find the difference between biological age and chronological age. Biological age is measured on a cellular and molecular level while chronological age is the number of years that have elapsed since birth. This study compared indicators of age of irradiated and normal subjects. There were 9 indicators including skin elasticity, systolic blood pressure and visual activity that were used to find the biological age of the subjects. These indicators were picked out of a wider array because they had the clearest correlation with age and were easily measurable. These indicators were measured routinely for subjects who had been irradiated over 10 years. In order to correlate the results, age was expressed as a function of the indicators which allowed graphs to be produced.
Results:
The results showed a correlation between radiation and higher biological age (than chronological age). For both males and females, the best indicator of age was skin elasticity while the poorest indicator was serum cholesterol. Across all indicators, age related changes were shown clearly after 40, but irradiated and normal subjects showed few changes before 40.
Therefore, a prediction about biological age could only be made for individuals above 40.
Generally, before 40, there is little difference in the rate of death by natural causes, there is a steep increase, however, after 40. This is because, after 40 the blood pressure increases, skin elasticity degrades and visual acuity decreases. Since these were the indicators measured in the study there were few observations and variations for the subjects below 40 years of age. Thus the study is only accurate for ages above 40.
The study was limited by the number of participants, and had many variables such as chronological age, sex, and radiation level. Each of these had to be accounted for when processing the data accumulated from the study.
In order to apply the results of this study to real life radiation victims, ageing related indicators for below 40 must be found and the data must be correlated with mortality rate as it is the only 100% accurate indicator of biological age and can thus validate the study. After which this concept could be used to predict the biological age of a person, which would allow for better treatment of radiated people.
Works Cited
Hollingsworth, J. W., et al. “Correlations between Tests of Aging in Hiroshima Subjects--an Attempt to Define “Physiologic Age”.” The Yale Journal of Biology and Medicine, vol. 38, no. 1, 1 Aug. 1965, pp. 11–26, www.ncbi.nlm.nih.gov/pmc/articles/PMC2591119/?page=16. Accessed 7 June 2024.
“Mortality Rate - an Overview | ScienceDirect Topics.” Www.sciencedirect.com, www.sciencedirect.com/topics/nursing-and-health-professions/mortality-rate.
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