Our results clearly show the importance of amount, duration and type of smoking in relation to mortality. Average cigarette smoking reduced life expectancy at age 40 by about 7 years, and heavy cigarette smoking reduced life expectancy even more. The average cigar or pipe smoker lost about 5 life‐years. Smoking decreased total life expectancy, and also decreased the number of disease‐free years of life, but to a smaller extent. Moreover, stopping cigarette smoking at age 40 increased the total life expectancy by about 5 years and the number of disease‐free years of life by about 3 years.
The major strength of this study was the collection of detailed information on smoking habits at each of seven examination rounds during 40 years of follow‐up. This enabled us to study the long‐term effects of cigarette as well as cigar or pipe smoking on mortality and life expectancy. Moreover, detailed data on potential confounders made it possible to study the independent effect of smoking. Adjustment for potential confounders reduced the number of life‐years lost by half a year.
This study also has weaknesses. Firstly, the Zutphen Study had a relatively small study population, which may have led to less precise results. Secondly, the number of never smokers was also very small, and we were therefore forced to combine men who stopped smoking for
10 years with men who never smoked in our reference group. Because studies suggested that mortality risk after 10 years of smoking cessation is comparable to that in never smokers,2,20
we used this cut‐off value. However, more recent studies showed that mortality risk is comparable to that in never smokers only after 10–1521,22,23,24
years of cessation, and so the differences in life expectancy might have been underestimated. Thirdly, the Zutphen Study started in 1960 with 872 men. The cohort of men who survived until 1985 was expanded with an additional cohort of 559 men. However, as this additional cohort of men was from the same birth cohort as the men who started the study in 1960, it is unlikely that bias was introduced.
Our findings confirmed results from others that also showed an increase in all‐cause mortality risk with cigarette smoking duration and the number of cigarettes smoked.9,13,14,15,20,23,27,28,29,30
After the adjustment for the prevalence of MI, stroke, DM and cancer, only cigarette smoking duration was found to be associated with lung cancer mortality. By omitting this adjustment for chronic disease prevalence, both smoking duration as well as the number of cigarettes smoked were found to be strongly associated with total cancer and lung cancer mortality. This result confirms those from other studies.9,10,11,15,20,28,29,30
In addition, we confirmed the results of other studies which showed dose–response relationships between smoking duration and COPD mortality.9,15
In accordance with other studies,6,7
the effects of cigar or pipe smoking on mortality were weaker compared with the effects of cigarette smoking. To our knowledge, we are the first to report on the effects of exclusive cigar or pipe smoking on life expectancy. This study found that the effects on life expectancy observed for cigar or pipe smoking were close to those observed for cigarette smoking. Exclusive cigar or pipe smoking reduced life expectancy by about 5 years, whereas cigarette smoking reduced life expectancy by about 7 years.
In the British Doctors Study,4
the Framingham Heart Study31
and the Cancer Prevention Study II,32
the reduction in life expectancy due to smoking was about 9 years. The difference in the reduction in life expectancy compared with this study may be due to several factors. Firstly, life expectancy within these studies was assessed at different ages. Secondly, men who stopped smoking
10 years ago were not included in the reference group. Thirdly, the adjustment for possible confounders was not carried out in these studies and, finally, the average amount smoked might have been higher compared with that in this study. Both the British Doctors Study29
as well as our study found that heavy cigarette smokers lost 9–10 life‐years, indicating that the amount smoked is associated with reductions in life expectancy.
In accordance with the British Doctors Study4
and the Cancer Prevention Study II,32
we found that smoking cessation has beneficial effects on life expectancy. These studies as well as this study found a substantial increase in life expectancy of about 3 years when stopping smoking at age 60. The main focus in smoking prevention programmes is preventing smoking initiation. The results from this and other studies indicate that the persuasion of smokers to quit smoking, even later in life, should be another important focus from a public health perspective.
What this study adds
Cigarette smoking has been recognised as a health hazard for many years, but much less is known about the adverse effects of long‐term cigar and pipe smoking. This study shows that long‐term average cigarette smoking reduces life expectancy by 7 years and long‐term heavy cigarette smoking reduces life expectancy by 9 years. Cigar or pipe smoking reduces life expectancy by 5 years. Adjustment for potential confounders reduces the number of life‐years lost due to smoking by half a year.
In this study, the reduction in the number of disease‐free years of life due to smoking was comparable between the different types of smoking. Other studies also addressed the differences in the number of disease‐free years of life.31,33,34
Although these studies defined disease‐free years of life differently from this study and did not distinguish between different types of smoking, the overall conclusions were similar. Never smokers and quitters live longer than continuing smokers, and they also spend more years of life in better health.
In summary, cigarette and cigar or pipe smoking reduces life expectancy and the number of disease‐free years of life. However, the number of life‐years lost due to cigar or pipe smoking is fewer compared with cigarette smoking. Both the number of cigarettes smoked and smoking duration are strongly associated with mortality risk and the number of life‐years lost. Although our results indicate that the effects will be larger the earlier one quits, even stopping at age 60 has major benefits on life expectancy.