We’re living longer but 125 years is the most likely limit, say researchers
Biologists and demographers have it wrong, say geneticists – there’s nothing to show the maximum human lifespan can go on rising. In other news: study reveals no long-term benefits from wearing fitness trackers
Maximum human lifespan has already been reached
People are living longer than ever – and will continue to do so – but the maximum lifespan for humans will soon be reached, a study published online in the journal Nature shows. That ceiling is 125 years, according to scientists at Albert Einstein College of Medicine in New York. The oldest person on record was 122-year-old Frenchwoman Jeanne Calment, who died in 1997.
“Demographers and biologists have contended there is no reason to think that the ongoing increase in maximum lifespan will end soon,” says senior author Jan Vijg, professor and chair of genetics at the college. “But our data strongly suggest that it has already been attained and that this happened in the 1990s.”
Vijg and colleagues analysed data from the Human Mortality Database, which compiles mortality and population data from more than 40 countries (China is not part of this). Since 1900, those countries have shown a continuing increase in average life expectancy. But gains in longevity peaked at about 100 years and then declined rapidly, regardless of the year people were born.
Looking at data from the International Database on Longevity, the researchers focused on people verified as living to age 110 or older between 1968 and 2006 in the US, France, Japan and the UK – the four countries with the largest number of long-lived individuals. Age at death for these supercentenarians increased rapidly between the 1970s and early 1990s, but reached a plateau about 1995.
The researchers put the average maximum human lifespan at 115 years, and 125 years as the absolute limit of human lifespan. In a given year, they say, fewer than one in 10,000 people anywhere in the world will live to 125 years.
Says Vijg: “While it’s conceivable that therapeutic breakthroughs might extend human longevity beyond the limits we’ve calculated, such advances would need to overwhelm the many genetic variants that appear to collectively determine the human lifespan.”
Gene defect points to food choices
Prefer potato chips over ice cream? It may have to do with biology: a new University of Cambridge study shows a direct link between preference for high-fat foods and specific genetic variants in humans.
In the new study in Nature Communications, researchers gave participants an all-you-can-eat buffet of chicken korma with three options manipulated to look and taste the same, but in which the fat content provided 20, 40 or 60 per cent of the calories. They tested lean people, obese people, and people who were obese because they have a defect in a gene called MC4R, which leads to eating a lot more fat but, unusually, a lot less sugar. It’s estimated about one in 100 obese people have a defect in this gene.
People were allowed to eat freely from the three kormas. Although there was no overall difference in the amount of food eaten between the groups, individuals with defective MC4R ate almost double the amount of highest fat korma than lean individuals ate and 65 per cent more than obese individuals.
Next, people were given Eton mess, a dessert of strawberries, whipped cream and broken meringue. Again, there were three options from which participants could freely choose, with sugar content providing eight, 26 or 54 per cent of calorific content, but with the fat content fixed. Individuals with defective MC4R liked the highest-sugar dessert less than their lean and obese counterparts and ate less of all three desserts compared to the other two groups.
Activity trackers unlikely to encourage physical activity
Activity trackers made by Fitbit, Jawbone, Garmin and others are unlikely to help people become
more active, according to a new
study from the Duke-NUS Medical School in Singapore. Published in
The Lancet Diabetes & Endocrinology, the study recruited 800 working adults and randomly assigned them to a control group, a tracker only group, or tracker plus one of two types of rewards schemes for meeting weekly step goals. One reward group accrued rewards in cash and the other had the rewards go to a charity of the individual’s choosing.
Findings showed that, regardless of the physical activity levels of participants before the study began, activity trackers alone or when combined with rewards designated for charity did not increase activity levels. In fact, nearly half of participants were no longer wearing their trackers by the end of the six- month assessment period.
In contrast, both active and inactive individuals offered cash rewards significantly increased activity levels from their baseline over the six months, and nearly
90 per cent continued to wear the trackers.
However, at the end of 12 months – six months after the incentives were removed – this group showed poorer step outcomes than the tracker-only group, suggesting that removing the incentives may have demotivated these individuals.
Despite the step differences, activity trackers, with or without incentives, did not lead to
noticeable improvements in health outcomes.