If there is one thing that worries a pension trustee more than tumbling stock markets, it is longevity risk, or the chance his members will live longer than expected.

Some banks have begun to offer derivatives that promise to swap away this risk, notably JP Morgan and Goldman Sachs. Although it is early days for such longevity hedging, investors may be able to benefit from rising life expectancy by investing in an obscure form of asset that is linked to it, according to one academic.