John Burke, 86, was assaulted during a burglary in Hackney, north London, early on 29 September last year.
He was taken to hospital and discharged a few hours later, but died at home the next day.
Ashley Malcolm, of Hackney, east London, had headbutted him when he was challenged during the break in.
Malcolm admitted killing the pensioner and, on Thursday, Judge Simon Mayo KC sentenced him to a lengthy period in prison.
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