Our lives can be separated into three main phases: development, aging, and late life. However, after studying a group of fruit flies, a group of researchers now suggests there is a fourth phase immediately preceding death. Scientists have given this new phase the name “death spiral” and believe it is as relevant to our own lives as it is the flies studied.
“We believe this is part of the process of, basically, genetically programmed death,” Laurence Mueller, chair of the Department of Ecology and Evolutionary Biology at the University of California, Irvine, told reporters at Live Science.
By studying fruit flies, researchers have been able to identify the spiral toward death in the drop of reproductive rate. A study published in The Journals of Gerontology in 2015 found that the first day a female fly laid zero eggs was a significant predictor of death and “indicators of fecundity started to decline about 10 days before the young female flies laid zero eggs.” The researchers think that the same thing leading to the flies’ death is affecting their ability to reproduce.
Mueller noted that the timing of this decline matches another previous estimate of the death spiral’s duration for the fruit fly. 10 days is typically about a third of a fly’s life, he noted. Another study on Mediterranean fruit flies from 2002 found that 97 percent of males started lying upside down about 16 days before death—relatively equal to the timing of fecundity.
Scientists hope the death-spiral research in fruit flies could someday give clues about the decline of humans prior to death. Citing a 2008 study published in Proceedings of the National Academy of Science, Mueller, and his colleagues noted people may also experience similar spirals. In that particular study, researchers studied data collected on the physical and cognitive abilities of 2,262 Danish people aged 92 to 100. They concluded the physical and cognitive scores of individuals who died within the first two years of the study were significantly lower than the score of those who were still alive at the end. The researchers specifically studied grip strength, the ability to complete daily activities, and cognitive impairment.
Mueller suggests this death spiral could be the reason we see an increase in disability just before a person dies. The study of fruit flies and other organisms could give scientists a window into how this could work for humans. The next step will be to selectively breed the flies to create groups that experience death spirals of differing durations. This will allow them to determine which genes were changed to reduce the length of the death spiral and potentially identify similar genetic markers in the human genome. Interestingly, humans are genetically similar to fruit flies—with 75 percent of disease-causing genes in humans also present in fruit flies.
The ultimate goal is to improve people’s quality of life as they reach the end and to save the burdensome costs associated with end-of-life health care.