Why Do Astronauts Live So Long?

Apollo 11's Buzz Aldrin and Michael Collins, pictured in 2017 for the 48th anniversary of the moon landing. (Source: Kat Vinton)

Last year saw the fiftieth anniversary of Apollo 17, the final mission of the program and the most recent time humans have visited the moon. In spite of this long gulf of time, many of the Apollo missions’ astronauts are still alive, well into their eighties and nineties. It raises the question, what’s the cause of this spike in astronaut longevity? Can it simply be attributed to the physical fitness demanded of these astronauts during their missions, or is there some x factor that can explain it? If there is some secret to living longer, could it be applied to people living on Earth without needing to make the trip to space?

The question is no idle concern, with much research being devoted to the subject. Over the last few years, Kuniaki Otsuka out of Tokyo Women’s University along with his associates have published numerous articles on how a zero-G environment impacts core biological functions like the cardiovascular system, circadian rhythm, and unconscious brain functions. Otsuka’s work builds on top of a growing field of research of outer space gerontology. For example, Caenorhabditis elegans, a tiny nematode worm, has been found to suppress polyglutamine aggregates during and after spaceflight that lead to excess protein production and resulting cell death.

A caenorhabditis elegans worm, used to study the effects of cells in zero-G environments.

As a zero-G environment is a major disruption to the entire human body, Otsuka’s research covers a wide range of bodily functions. Participants in the various studies were astronauts aboard the International Space Station who wore EKG devices to measure changes in the electrical signals produced by their hearts. The findings were quite impressive: sleep quality improved, heart-rate variability was stable, and even the unconscious mind seems capable of regulating the cardiovascular system to adapt to zero-G conditions. These things themselves don’t magically reverse the aging process, but since bad sleep and poor heart health are two of the biggest predictors of old age decline, they’re quite illuminating.  

It would seem that there are some unusual health benefits from exposure to a zero-G environment, but along with these benefits are plenty of hazards. Ultimately, humans are evolved for one specific planetary environment, and any deviation from that comes with risks. Astronauts on the International Space Station have to maintain a rigorous exercise schedule with specially outfitted equipment, otherwise they face bone and muscle atrophy. Even with this routine, the lack of gravity leads to fluid imbalances, causing the well known “puffy head, bird legs” among astronauts. A zero-G environment may have its benefits to astronauts, but it’s a far cry from a miracle cure.

The International Space State, where Otsuka's research was conducted. (Source: NASA)

When he stepped off the lunar lander in 1969, Buzz Aldrin was 39 years old, not exactly a spring chicken. Last month he celebrated his 93rd birthday. It remains an unsettled issue what exactly is the explanation for his and his fellow astronauts' long life spans. As manned space flights become more prevalent in the coming years, we may gain more insights into this unusual phenomenon, and how, maybe, it could be replicated here on Earth. For now though, it remains one of many unsolved mysteries of outer space that has yet to be answered.

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Otsuka K, Cornelissen G, Kubo Y, et al. Anti-aging effects of long-term space missions, estimated by heart rate variability. Scientific reports. 2019;9(1):8995-12. doi:10.1038/s41598-019-45387-6

Otsuka K, Cornelissen G, Furukawa S, et al. Astronauts well-being and possibly anti-aging improved during long-duration spaceflight. Scientific reports. 2021;11(1):14907-14907. doi:10.1038/s41598-021-94478-w

Otsuka K, Cornelissen G, Furukawa S, et al. Unconscious mind activates central cardiovascular network and promotes adaptation to microgravity possibly anti-aging during 1-year-long spaceflight. Scientific reports. 2022;12(1):11862-11862. doi:10.1038/s41598-022-14858-8