The BBC do report that:
But immigration is not a factor apparently, which seems odd to me.
'4. The UK's population is ageingThe ageing population is certainly a major factor - and it's one that all health systems in the world are struggling with. Medical advances have meant that people are living longer. When the NHS was created, life expectancy was 13 years shorter than it is now.'
Mind you I was slightly shocked to see the BBC report these two facts: