Key to longevity? Breathe LESS oxygen, says study

Many believe that restricting how much they eat or obsessive exercise can extend their lifespan.

But scientists at Massachusetts General Hospital have now suggested a third way; take in less oxygen.

In a study on mice, they found that rodents kept at 11 percent oxygen — equivalent to the base camp of Mount Everest — lived 50 percent longer than those kept at ambient levels.

They said breathing in less oxygen could reduce damage to cells and prompt them to clear out and recycle damaged parts, slowing the aging process.

It was not clear whether the study results could be replicated in humans, but previous papers have suggested that humans who live at higher altitudes live longer than their peers. But they are also at higher risk for low birthweights and stunted growth, which scientists say may be driven by the lack of oxygen.

In the study, the first to examine oxygen restriction in mice, the researchers used rodents that had been bred to age rapidly.

They were split into two groups at four weeks of age, with half staying at ambient oxygen levels (21 percent) while the rest were placed in a chamber that drove the levels down to 11 percent.

Each was offered adequate food and water and scientists then monitored the mice until their deaths.

Results showed that mice living at ambient oxygen levels lived for a total of 15.7 weeks on average.

But those who were exposed to restricted oxygen levels lived for nearly eight weeks longer — with a lifespan of 23.6 weeks.

Mice in both groups ate about the same amount of food. 

The results back up previous research, which has also found that oxygen restriction extends the lifespan of yeast, worms and fruit flies.

The researchers now hope to test oxygen restriction and longevity further to back up their findings, possibly in other animals.

It was not clear how humans might be exposed to lower oxygen levels continuously to help extend their lifespan. 

But as well as spending several hours a day in a low oxygen chamber, the paper also pointed to how people who live at higher altitudes live longer.

Other papers have warned, however, that people born at these higher levels may have lower birthweights and stunted growth due to the lack of oxygen.

The researchers suggested that oxygen restriction may slow aging because it triggers a pathway in cells that causes them to clear out and recycle damaged parts more frequently.

They also suggested that cells were facing less damage from oxidative stress, or the molecules released when oxygen is used as energy that can damage DNA.

They also suggested there was a reduction in neurodegeneration and inflammation levels in the body.

The above graph shows the average lifespan of mice in the two groups

Limitations of the study include that it was carried out in mice rather than humans and that low oxygen exposure may be needed from a young age to trigger the effects.

Dr Roger Roberts, a pulmonologist who led the study, and others said in the paper: ‘Epidemiological evidence suggests that lifelong oxygen restriction might slow the aging process in humans.

‘Though there are many potential confounders to this finding, recent cross-sectional studies in Bolivia have demonstrated significant enrichment for nonagenarians and centenarians at very high altitudes. 

‘There is also data that suggests there are potential benefits of moving to altitude in adulthood.’

Previous research has suggested that people who live at high altitudes live longer than their sea-level-dwelling peers.

One paper found that out of the top 20 counties with the highest life expectancy in the US, 11 for men and five for women were at about 5,900 feet above sea level.

Researchers have previously suggested that a chronic lack of oxygen triggers pathways in cells that cause them to repair damage, reducing age-related decline.

Other methods to reduce the pace of aging that have been suggested include consuming less food.

Research in primates on this method has been inconclusive, but some studies in humans suggest that it may be able to boost life expectancy.

Another method highlighted is getting adequate exercise, with physical activity associated with a wide range of health benefits including better blood sugar control and a lower risk of many chronic diseases.

But studies have also warned that obsessively exercising — getting more than five hours a week of vigorous cardiovascular exercise and not getting at least one rest day per week — can actually have the reverse effect and shorten lifespan.

They say this is because it raises the risk of joint and heart problems that could lead to an earlier death.  

The latest paper on chronic oxygen restriction in mice was published in the journal PLOS Biology.