London, April 12 (IANS): The wait for the coveted Nobel prize has just got a little longer.

The time lag between reporting of a major scientific discovery and awarding it with the Nobel prize has grown over the years, with 20 years now being the norm, according to a study.

Given that the Nobel prize cannot be awarded posthumously, this lag threatens to undermine science's most venerable institution, says Professor Santo Fortunato of Aalto University in Finland, who conducted the study.

Many aspiring laureates may themselves have died by the time the medal is due to be presented, the study found.

Before 1940, Nobel prizes were awarded more than 20 years after the original discovery for only about 11 percent, 15 percent and 24 percent of physics, chemistry and physiology, and medicine prizes, respectively.

But by 1985, delays of this order were featuring in 60 percent, 52 percent and 45 percent of the awards in these respective fields.

And the wait could be much longer in some cases. Take, for instance, noted Indian-American astrophysicist Subrahmanyan Chandrasekhar who shared the 1983 Nobel prize in physics for his work on stellar structure and evolution that was done in the 1930s.

As the wait lengthens, the average age at which laureates are awarded the prize also goes up.

The average age for all the physics laureates between 1901 and 2013 (when awarded) is 55.

The youngest physics Nobel laureate Lawrence Bragg was 25 years old when he was awarded the Nobel Prize with his father in 1915.

The oldest Nobel laureate in physics to date is Raymond Davis Jr., who was 88 years old when he was awarded the Nobel Prize in 2002.

By the end of this century the predicted average age among prize-winners for receiving the award could even exceed his or her life expectancy, said the study.

The findings of the study appeared in the journal Nature.