



of recent mortality improvements in the UK population would suggest that we should expect higher improvements in future than many longevity actuaries are allowing for in their assumptions. How can that be justified?An important constituent of past UK mortality improvements is that caused by the reduced prevalence of smoking, which arises both from people quitting and from increasing numbers not taking up the habit. The relatively low current levels of smoking mean it is not possible for the magnitude of past reductions to be repeated in future. Additionally, new technologies like e-cigarettes look set to affect future changes in mortality improvements.We can derive an estimate of how much recent mortality improvements have been driven by reductions in smoking, using information on the effect smoking has on the risk of death from specific causes combined with data segregated by cause of death.The effect of e-cigarettes on future mortality rates is currently not certain. It will depend both on their impact on health, and on whether they lead current smokers to reduce their consumption of conventional tobaccos, or whether they entice a new generation to develop a nicotine habit.A recent Public Health England report concluded that e-cigarettes are "95% less harmful" than smoking and, according to one of the authors, "may well be much, much lower than that". If borne out, this would suggest that the mortality of e-cigarette users with no history of tobacco smoking would be only marginally higher than that of lifelong non-smokers. Whether existing smokers use e-cigarettes instead of, or alongside, conventional tobaccos would therefore become the key question.Surveys commissioned by the public health charity Action on Smoking and Health (ASH) suggest that nearly 40% of e-cigarette users in Great Britain are ex-smokers, while the remaining 60% continue to smoke cigarettes alongside (the number of e-cigarette users who have never smoked is negligible).ASH figures suggest that, after a few years of rapid growth, e-cigarette usage in Great Britain levelled off in 2015. But with the Public Health England report suggesting that e-cigarettes should be prescribed by the NHS in future to help smokers quit, usage could soon rise once more. The implications of e-cigarettes for future mortality improvements are clearly uncertain. However, if the NHS were to roll out such a policy, (conventional) smoking prevalence could reduce significantly again - providing a boost to the pace of improvements in mortality.The most credible datasets for analysing mortality improvements, such as UK population and death data published by the Office for National Statistics (ONS), are not categorised by smoking status. However, ONS does publish cause-of-death data.Relative mortality risks by smoking and cause-of-death status can be sourced from the US Cancer Prevention Study II (CPS-II), the results of which the NHS considers to be transferable to the UK. Combining these two data sources with information on smoking prevalence, also published by ONS, allows us to derive smoking-specific rates of mortality improvement.CPS-II provides relative mortality risks for three smoking categories - current smokers, ex-smokers and those who have never smoked. The ratio of smoker to 'never-smoked' mortality ranges from around 200%, for pneumonia and influenza among males, to more than 2,000% for cancer of the trachea, lung and bronchus. In total, smoking-related diseases covered within CPS-II account for just over half of all deaths among annuitant/pensioner ages in recent years, and a slightly larger proportion for males than females.The prevalence rates provide 'exposures' in each category, while deaths are apportioned according to the CPS-II relative risk ratios. From these, we can calculate smoking-specific central rates of mortality, and the rates of improvement over time, for each smoking category.Figure 1 shows crude annual rates of mortality improvement in five-year age-bands for males aged 60 to 84 over a 30-year period ending in 2012. It indicates that these were generally very similar for all three smoking categories and that each had lower improvements than the male population as a whole, which were boosted by just over 0.5% a year by the reducing prevalence of smoking over the period. People often query this concept, asking how aggregate improvements can exceed those of each category. But as lifelong non-smokers and ex-smokers have lower rates of mortality than current smokers, a fall in smoking prevalence in the general population produces a mortality 'dividend', and is reflected in the higher mortality improvements for the "all" group in Figure 1.



