It is common knowledge that smoking is the primary catalyst for lung cancer, the second and sixth highest cause of death for males and females respectively in 2012. However, it may not be so widely known that male and female mortality has been affected differently by changing prevalence of smoking. Can the patterns in observed male-smoker mortality improvements shed any light on future female-smoker mortality improvements?
A recent BBC News story highlighted that the number of new female cancer cases increased to over 20,000 in 2012. This continues the trend of increasing lung cancer incidence rates amongst females, whereas rates for males continue to decline.
This marked difference is driven by differences in smoking habits across the sexes. Male smoking prevalence peaked in the 1940s and has been decreasing steadily ever since, whereas the number of female smokers continued to increase following the end of the Second World War, peaking in the 1970s.
Chart 1: Cigarette smoking prevalence in Great Britain, 1948-2012, males and females aged 16 and over
Source: Cancer Research UK
"We can expect lung cancer incidence for females to level off and begin to decrease in the coming years"
Our recent research has shown that male all-causes mortality rates fell by around 0.5% each year between 1982 and 2012 due to the decrease in smoking prevalence.
The question is whether this delay between the peak in male and female smoking prevalence can give us an insight into future improvements for females. Lung cancer is now a source of improvement in mortality for males as the largest cohorts of life-long smokers have already died. Incidence rates began to decline approximately forty years following the peak in prevalence for males, especially at the oldest ages. A similar period of time since the peak in prevalence has now passed for females and the cohorts with the largest proportion of female life-long smokers are now at the ages critical for pension schemes and annuitants, so we can expect lung cancer incidence for females to level off and begin to decrease in the coming years.
The effect of reducing smoking prevalence on male mortality improvements has already largely been felt; future improvements in lung cancer mortality are now only likely if survival rates improve; perhaps as a result of new guidelines issued recently by the health watchdog, NICE, aimed at diagnosing patients at an earlier stage or the new immunotherapy treatments recently approved.
In contrast, we can expect the past pattern of deteriorating lung cancer mortality for females to switch to a pattern of improvements. The impact may not be as marked – the prevalence of female smoking was never at the level of male smoking; peaking at approximately 45%, compared with 65% for males – but is one argument as to why future female improvements could be higher than male improvements.