Harvard expert shares little-known fingernail sign that shows your 'biological age'

Dr David Sinclair, genetics professor at Harvard Medical School, previously spoke about the surprising fingernail sign on a podcast

A leading longevity expert has highlighted a surprising nail sign that could hint to our 'biological age'. Dr David Sinclair, a genetics professor at Harvard Medical School, has spent his career delving into the reasons behind ageing and how to decelerate its impact.

Although the average life expectancy in the UK hovers around 80 years, Dr Sinclair points out that it's possible to age more rapidly than the number of candles on your birthday cake. This concept, known as 'biological age', assesses the age of your cells and tissues, and one surprising marker might just be found on your fingernails.

"I learned this a number of years ago when I was at MIT (Massachusetts Institute of Technology)," Dr Sinclair said on the Lifespan podcast in 2022. "That the rate of your nail growth is a really good indicator of how you are ageing or not ageing. And so, every time I have to cut my nails I'm thinking, 'How long ago did I cut my nails?'"

Dr Sinclair's assertions are based on a study from 1979 which examined the pace of nail growth in dogs and humans over several years. For humans, linear nail growth saw an increase 'well into the third decade of life'.

However, from the ages of 25 to 100, there was a gradual decline of about 0.5% per year from 'an average of 0.9 mm per week in the third decade'. The study also noted that the rate of decrease was more pronounced in men until they reached their '60s.

"They glued on these little measuring tapes on to people's nails and measured them over years, in fact," Dr Sinclair explained. "And there was one individual - Mr Bean actually - who measured his nails for most of his life.

"...We have that graph and actually, looking at thousands of people, we now know for sure that the rate of nail growth decreases about half a per cent per year. And if you measure that, it's a really good indicator of how old you are biologically.

"So, I don't do that, but I do pay attention to whether my nails are slowing down in their growth or not." While the mechanism behind this is not well understood, scientists speculate that decreased blood circulation may lead to fewer nutrients reaching the fingernails, resulting in stunted growth.

Other factors, such as exercise habits, genetics, and diet, can also impact 'biological age'. For instance, a high-fat diet can cause oxidative stress and inflammatory damage, potentially contributing to 'faster ageing'.

Nevertheless, it is essential to note that unusual fingernail texture can be a symptom of various health issues, including hyperparathyroidism, fungal infections, and anaemia.