Post-retirement life expectancy for men and women is declining, according to analysis of Office for National Statistics (ONS) data, though experts say it is likely a "blip" rather than a longer term trend.
Estimates of life expectancy at age 65 in 2012-13 have been revised in successive ONS publications, according to retirement provider Partnership, possibly reflecting an unusually high death rate caused by influenza and low temperatures.
It said ‘period' life expectancy at age 65 in 2012-13 was most recently estimated to be 18.3 years for men and 20.6 years for women - significantly below the respective 19 years and 21.3 years reported in the ONS's forecast published in 2009.
Period life expectancy is a less common interpretation of life expectancy which calculates mortality rates for all ages in the same year.
Richard Willets, director of longevity at Partnership, said: "Have we have been over optimistic about life expectancy in the UK? Or is this simply a plateau and we will see a return to growth in years to come?
"While this is unlikely to have a significant impact on the man in the street in the immediate future, if this trend continues the next generation may see larger private pension pay outs or a static state retirement age. A review of the pension age increases is scheduled for the next Parliament but in the meantime, researchers with an interest in longevity and pensions will be watching the situation closely."
The findings come from the ONS's latest National Population Projections, which show the UK population is projected to increase from an estimated 63.7 million in mid-2012 to 68 million by mid-2022 and to 73.3 million over the 25-year period to mid-2037.
According to the ONS, the UK population is projected to reach 70 million in 2027. It also said the number of people aged 80 and over in the UK will more than double to six million by mid-2037.
John Fox, managing director of Liberty SIPP, said the latest ONS figures will pile more pressure on an already-stretched state pension system.
"From a pensions perspective, we are at red alert. Unless the government accepts the magnitude of the problem and looks into a way of making pension saving more accessible and part of everyday life, its actions are as irresponsible as not stocking up on vaccine for an impending epidemic. Successive governments have conspired to build the precipice we now stand on, and so they either need to get real or get out of it altogether."
Steve Wilkie, managing director of Responsible Life, said the data was a "stark reminder" of the extent to which Britons are living longer. "The penny is dropping that, for lots of us, retiring at 60 or 65 simply won't be an option," he said.
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