Following research gathered during the Future Mortality project, Professor Fanny Janssen discusses the value of understanding the impact of past and anticipated future trends in smoking-, alcohol-, and obesity-attributable mortality on past and future life expectancy.
Life expectancy, the average number of years people can expect to live, is an important summary measure of health. In Europe, nowadays, men can expect to live on average 75 years and women 81 years.
Forecasting how life expectancy will develop in the future is essential for public policy, social security, and healthcare planning. Most mortality forecasts, however, rely on a mechanical extrapolation of past mortality trends, which could easily result in unreliable outcomes because temporal fluctuations in mortality trends are generally ignored.
While life expectancy has increased overall as a result of socioeconomic and medical progress, past trends in life expectancy in Europe were characterised as well by periods of stagnation or even decline. Lifestyle factors, particularly smoking, alcohol abuse, and obesity, are important causes of these temporal fluctuations in mortality trends in Europe, albeit differently so by country and sex.
These lifestyle factors, like true epidemics, tend to first become increasingly prevalent in a population resulting in increased mortality and slower life expectancy improvements, followed (eventually) by a decline in their prevalence and associated mortality, resulting again in higher improvements in life expectancy. In Northwest Europe, past increases in smoking prevalence among men led to stagnating male life expectancies in the 1950s and 1960s, but these picked up again after smoking declined. Among women, who took up smoking later than men, increases in life expectancy have stagnated in more recent decades. The large increases in alcohol consumption and alcohol-attributable mortality between 1990 and 2005 in Eastern Europe contributed to the stalling of life expectancy improvements in Eastern Europe in this period. And the stagnation in life expectancy improvements since approximately 2011 in the US and the UK, but also in other selected European countries, can be partly attributed to the high obesity prevalence and obesity-attributable mortality in these countries and to the increasing impact on life expectancy levels of past large increases in obesity prevalence.
The Future Mortality research project
In my recently finalised research project Future Mortality, we initially studied the individual and combined effects of smoking, alcohol abuse and obesity on levels and trends in life expectancy for 30 European countries. We subsequently introduced a novel mortality forecasting technique that takes into account both the impact of smoking, obesity and alcohol on mortality trends and the mortality experience of forerunner populations.
Based on data from 30 European countries, we found for 2014 that the average combined impact of smoking, obesity, and alcohol on life expectancy at birth was 5.8 years among men (3.4 years for smoking, 1.8 years for alcohol and 1.3 years for obesity). Among women, the impact was much lower, at 2.3 years (0.8 years for smoking, 0.5 years for alcohol, and 1.2 years for obesity). In other words, without these three lifestyle factors, life expectancy at birth in Europe would have been 5.8 years longer for men (currently 75 years) and 2.3 years longer for women (currently 82 years).
The impact of the three lifestyle factors on life expectancy is, however, not stable over time. Among men in the 30 European countries studied, the average combined impact of smoking, obesity, and alcohol on life expectancy at birth declined from 6.6 years in 1990 to 5.8 years in 2014. This was mostly due to a decline in smoking-attributable mortality. Among women, the average combined impact of smoking, obesity, and alcohol on life expectancy at birth actually showed an increase, from 1.9 to 2.3 years during the same period, due to, on average, increases in all three lifestyle factors. The three lifestyle factors combined also affected improvements in life expectancy at birth over time. Across the 30 European countries, the observed average increase in life expectancy at birth between 1990 and 2014 was 5 years for men (from 69.3 to 74.3 years) and 4 years for women (from 77.3 to 81.2 years). Without the impact of smoking, obesity and alcohol, this increase would have been 4.2 to 4.3 years for both men and women.
The resulting stable and more uniform increase in life expectancy – without the impact of lifestyle factors – likely captures the underlying gradual increase in life expectancy in Europe, as a result of overall socioeconomic growth and medical progress. Furthermore, the results indicate that lifestyle ‘epidemics’ have the tendency to distort this general gradual increase in life expectancy, albeit differently so by sex, country and time period.
Based on this finding, we developed an integrative approach to the projection of life expectancy in the future. We argue that to obtain a reliable and robust mortality forecast, it is essential to distinguish between and separately predict (1) the general and gradual long-term mortality decline due to socioeconomic and medical progress that can be extrapolated in the future, thereby taking into account the mortality experiences of other countries, and (2) lifestyle factors that cause deviations from this general mortality decline as well as country and sex differences in this trend.
For the projection of the general and gradual long-term mortality decline, we used an established demographic mortality projection technique. The projection of lifestyle-attributable mortality is based on the separate projection of smoking-, alcohol-, and obesity-attributable mortality using more advanced projection methods that are both data- and theory-driven.
We project that life expectancy at birth, in the 18 European countries studied, will increase from, on average, 83.4 years for women and 78.3 years for men in 2014 to 92.8 years for women and 90.5 years for men in 2065. Compared to a benchmark Lee-Carter mortality extrapolation, and the forecasts by Eurostat and the United Nations, the projection results in higher future life expectancy values, more realistic differences in future life expectancy between countries and between sexes, and additional insights into what is driving future life expectancy values. More specifically, their projected e0 values in 2065 are 5 years higher for men, and 3 to 4 years higher for women compared to the 2020 Eurostat and United Nations forecasts.
Our findings of higher projected life expectancy values than those currently obtained, and of a rather steady long-term increase in life expectancy after the effects of smoking, obesity, and alcohol are accounted for, imply longer individual lifespans, more older adults in society than previously anticipated, and that a limit to human life expectancy is not within reach.
The novel approach, which distinguishes between the underlying long-term mortality decline and the remaining factors that cause deviations from this mortality decline, could be adopted as well to account for the impact of the COVID-19 pandemic on mortality and life expectancy.
Funding
The Future Mortality project by Professor Fanny Janssen entitled ‘Smoking, alcohol, and obesity, ingredients for improved and robust mortality projections’ (see www.futuremortality.com) was funded by the Netherlands Organisation for Scientific Research (NWO) (grant no. 452-13-001).
References
- Janssen, F., Trias-Llimós, S., and Kunst, A. E. (2021a). The combined impact of smoking, obesity, and alcohol on life expectancy trends in Europe. International Journal of Epidemiology, 50(3). doi: 10.1096/ije/dyaa273. https://academic.oup.com/ije/article/50/3/931/6082777
- Janssen, F., Barboutsos, A., El Gewily, S., and De Beer, J. (2021b). Future life expectancy in Europe taking into account the impact of smoking, obesity, and alcohol. eLife (10), e66590. doi: 10.7554/eLife.66590. https://elifesciences.org/articles/66590
Professor Fanny Janssen
Senior Researcher
Netherlands Interdisciplinary Demographic Institute (NIDI-KNAW) in The Hague
Honorary Professor in Mortality and Longevity
Population Research Centre, Faculty of Spatial Sciences, University of Groningen, the Netherlands
https://nidi.nl/en/employees/fanny-janssen/
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