9.3 Contribution of smoking to health inequality

Last updated: February 2022

Suggested citation:
Greenhalgh, EM, Scollo, MM, & Pearce, M. 9.3 Contribution of smoking to health inequality. In Greenhalgh, EM, Scollo, MM and Winstanley, MH [editors]. Tobacco in Australia: Facts and issues. Melbourne: Cancer Council Victoria; 2022. Available from: http://www.tobaccoinaustralia.org.au/chapter-9-disadvantage/9-3-contribution-of-smoking-to-health-inequality 

 

Ill-health and rates of premature death in Australia show a clear gradient across socioeconomic status (SES) groups.1 People who are more advantaged can afford better food and housing, better health care, and healthy activities. They also generally have more knowledge of healthy choices and behaviours.2

People who are disadvantaged are more likely to live with multiple risks to their health. Lower socioeconomic status is associated with higher rates of obesity, lack of adequate physical activity, and diabetes—especially so among Aboriginal and Torres Strait Islander communities.3

There is also a clear social gradient among people who smoke, with lower education and income linked with higher rates of smoking (see Section 9.1). Social differentials in smoking during pregnancy, cigarette consumption, duration of smoking, and exposure to secondhand smoke contribute substantially to socio-economic differentials in disease risk and mortality. Current smokers are much less likely than non-smokers to be in good health and the incidence of numerous diseases is significantly higher among smokers and recent ex-smokers than among long-time ex-smokers and never smokers.4, 5

This section outlines data on relative rates of poor health, disease, mortality, and life expectancy across SES groups, and also presents estimates of the contribution of smoking to these health disparities.

9.3.1 Socio-economic position, self-reported health status and smoking

People who live in disadvantaged areas are much less likely to assess their own health as excellent or good.5 Australians with lower incomes and education levels experience higher rates of arthritis, chronic respiratory disease, cardiovascular disease and mental illness compared with more advantaged groups in the population. The rates of stroke, coronary heart disease, and diabetes in low socio-economic areas are more than double that of those in the highest socio-economic areas.5

In 2019, only 35% of regular smokers participating in the National Drug Strategy Household Survey reported their overall health as ‘very good’ or ‘excellent’, compared to 50% of ex-smokers and 62% of never smokers. Ex-smokers were more likely to report heart disease, diabetes, and cancer than smokers and never smokers. Smokers were more likely to report asthma, chronic pain, and mental illness6 (see also Section 7.12).

9.3.2 Socio-economic position and illnesses known to be caused by smoking

Rates of chronic health conditions show a clear social gradient. In 2017–18, adults in the lowest socioeconomic areas were twice as likely to have chronic obstructive pulmonary disease (among people aged 45+), 2.2 times as likely to have diabetes, and 1.3 times as likely to have heart, stroke and vascular disease.7 In 2018, the lowest socioeconomic group had 1.9 times the rate of kidney and urinary diseases of the highest group, 1.8 times the rate of cardiovascular diseases, 1.4 times the rate of mental and substance use disorders, 1.7 times the rate of respiratory diseases, and 1.5 times the rate of cancer.1

The Australian Institute of Health and Welfare has estimated that lung cancer was the fourth leading cause of disease burden among men and the tenth leading cause of disease burden among women in 2018. For years of life lost, it was the third leading cause among men and the second among women. Lung cancer incidence is disproportionately high in those of lower socioeconomic status in Australia, with increasing incidence of lung cancer associated with decreasing socioeconomic status. In 2018, there was a clear pattern of decreasing rate of burden from lung cancer with increasing socioeconomic group.1   

A major report from the International Agency for Research on Cancer highlighted that cancer occurrence, causes, outcomes, and required control measures differ markedly both between and within countries, and such differences frequently reflect social inequalities in the distribution of cancer risk factors and access to prevention measures, early detection, treatment, and care. The report judged that about 40% of cancers are preventable by simple lifestyle changes, with key causes such as smoking and obesity being socially determined. The largest social inequalities were found for mortality rates of smoking- and alcohol-related cancers.8

Along with increasing a person’s risk of disease, smoking can also complicate treatment and worsen their prognosis (see Section 3.15). These poorer outcomes are more likely among smokers living in more disadvantaged areas, with data from the National Drug Strategy Household Survey showing that in 2019, the prevalence of smoking among people with particular health conditions was far higher in lower compared higher socioeconomic areas. For example, the prevalence of smoking among asthmatics in low socioeconomic areas was 30%, compared with 8% of asthmatics living in more advantaged areas. Similar patterns were seen for heart disease (16% versus 4%), hypertension (14% versus 5%), cancer (14% versus 4%), and chronic pain (28% versus 11%).6  

9.3.3 Socio-economic disparities in death rates from diseases known to be caused by smoking

Australians from lower socio-economic groups have a greater proportion of chronic disease mortality burden than those living in more advantaged areas.2 This sub-section presents information on socio-economic disparities in mortality rates from diseases associated with smoking, however it is important to note the influence and interplay of other health risk factors and social and economic deprivation across a life-course, in the contribution to disease and premature mortality. Section 9.3.5 provides a detailed discussion on quantifying the contribution of smoking to socio-economic differentials in health status; associations between childhood circumstances and health outcomes, smoking and intergenerational poverty are discussed further in Section 9.5.

In 2018, people in the lowest socioeconomic areas were 1.5 times as likely to die as people in the highest areas. They were more than twice as likely to die from potentially avoidable causes; i.e., from something that could have been avoided with timely and effective health care. The mortality rate of people in the lowest socioeconomic areas for all causes of death was 615 per 100,000 population, compared with 554 in the second group, 494 in the third, 451 in the fourth, and 405 for people in the highest socioeconomic areas. Death rates from some diseases tended to be higher for people in the lowest socioeconomic areas, compared with people in the highest areas. For example, during the period 2014–18, adults in the lowest socioeconomic areas were: 2.4 times as likely to die from chronic obstructive pulmonary disease; 2.0 times as likely to die from lung cancer; 1.6 times as likely to die from coronary heart disease; and 1.2 times as likely to die from cerebrovascular disease (mostly stroke).9

Another Australian report found that, compared with the highest two, people in the lowest two socioeconomic quintiles are: almost twice as likely to die from a cardiovascular disease such as stroke or heart attack; almost 40% more likely to die from cancer; more than twice as likely to die from a respiratory disease; and almost three times as likely to die from diabetes.10

Smoking rates are substantially higher among Aboriginal and Torres Strait Islander peoples (see Section 8.3), and tobacco is a causal, contributing or complicating factor in many diseases and conditions disproportionately experienced by Aboriginal and Torres Strait Islander peoples. See Section 8.7 for a detailed overview of morbidity and mortality caused by smoking among Aboriginal and Torres Strait Islander peoples.

Research in the UK11 and in other European countries,12-14 and the US,15, 16 has found similar differences in life expectancies between people with low and high education levels and socioeconomic status, with smoking contributing to such gradients. Studies of cancer mortality in the US also show disparities related to socioeconomic position, as well as ethnicity.17, 18

9.3.4 Socio-economic disparities in health-adjusted life expectancy

The AIHW’s latest burden of disease report shows that in 2018, a total of five million disability-adjusted life years (DALYs) were lost in Australia. DALYs refer to years of healthy life lost, either through premature death, or through living with ill health due to illness or injury. Across Australia, 1,065,700 DALY were considered ‘excess’ due to socioeconomic position (i.e., would have been avoided if the rate of burden had been the same as in the group with the lowest rate); this represents 21% of the total DALY. The excess burden was mostly from fatal burden. Table 9.3.1 shows the DALYs for each of the five socio-economic quintiles in 2018.1

Table 9.3.1 Disability-adjusted life years lost (DALYs), Australia, by socio-economic quintile, Australia, 2018

Source:  Australian Institute of Health and Welfare, Table 8.7 1

After adjusting for age, rates of DALYs were 1.6 times higher in the lowest SES quintile than in the highest. There was a clear association between increasing rate of burden and decreasing socioeconomic position for most disease groups, including smoking-related diseases such as cancer, cardiovascular disease, and respiratory disease. Rates of years lived in ill health or with disability were 1.4 times higher, and years of life lost due to premature death were 1.9 times higher, among the most disadvantaged group compared with the least. Rates of burden were 1.4 times higher in remote and very remote areas than in major cities.1

Tobacco use caused a total of almost 20,500 deaths in 2018, or more than one in every eight deaths (13%). In 2018, 8.6% of the disease burden in Australia was due to tobacco use, making it the leading single risk factor that contributed to disease burden and deaths. This equated to 430,903 DALYs from death and illness due to tobacco use.1.19 See Section 3.30 for more detail. Life expectancy among Aboriginal and Torres Strait Islander peoples is discussed in Section 8.7.

In the US, researchers examined the effects of a number of health risk factors, including smoking, on life expectancy and disparities in life expectancy in eight sub-groups of the population.  Individually, smoking and high blood pressure had the most profound effect on life expectancy disparities. They found that variation of life expectancies in the eight sub-groups would decline by 18% in men and 21% in women if the health risks (smoking, blood pressure, elevated blood glucose, and adiposity or obesity) had been reduced to optimal levels.20

A 2016 report from the UK highlighted how, despite substantial increases in life expectancy, the gap in lifespan between the richest and poorest is increasing for the first time since the 1870s. From 1879 to 1939, life expectancy increased among all groups but disproportionately among the poor, largely due to improvements in health, clean drinking water, and the introduction of mass vaccination. Since then, deaths have been increasingly caused by chronic rather than infectious diseases or environmental causes, which are often attributable to health behaviours such as smoking and poor diet—behaviours that are generally more prevalent among socioeconomically disadvantaged groups.21

9.3.5 Quantifying the contribution of smoking to socio-economic differentials in health status

Estimates of the contribution of smoking to social inequality vary, likely due to differences in study methodology and datasets. Estimates may also be affected by declines in smoking prevalence in developed countries, changing social demographics, latency of disease and death associated with smoking, and the emergence of other risk factors and their contribution to disease and mortality. This section presents research across time and using differing methods to quantify the contribution of smoking to health inequalities. Section 9.3.6 explores whether the inequalities in health outcomes and life expectancy are widening.

In 2015 in Australia, the lowest socioeconomic group experienced the greatest amount of burden attributable to tobacco use with 131,954 DALY (12% of total DALY) compared with 47,676 DALY (6.5%) in the highest socioeconomic group. The lowest group experienced a rate of attributable burden that was 2.6 times that of the highest group. In 2015, 191,824 attributable DALY due to tobacco use were considered ‘excess’ due to socioeconomic position (i.e., would have been avoided if the rate of burden attributable to tobacco use had been the same as in the group with the lowest rate). Forty-three per cent of the total attributable burden for tobacco use was excess due to socioeconomic group, which was mostly fatal: 157,225 years of life lost compared with 34,599 years of living with disability. The lowest group had the highest excess for total attributable burden: 78,770 (or 60%) of the group’s attributable DALY was excess in comparison to that of the highest socioeconomic group.22 Researchers estimated that in Australia, smoking could account for just over one-third of the excess deaths in the 1990s that would otherwise be attributed to lower levels of education.23 Data on deaths among men aged 40–69 years taking part in a prospective cohort study in Melbourne between 1990 and 1994 showed that the association between education and mortality was greatly weakened after taking smoking into account.

In the UK, researchers estimated that tobacco caused about two-thirds of the difference in risk of death across social class in men age 35–69 years.24 Another UK study estimated that smoking is responsible for nearly twice as many cancer cases in lower income groups compared to higher income groups: over 11,000 versus about 6,000.25 A four-country study (England, Wales, Poland and North America) reported that most social inequalities in adult male mortality during the 1990s were due to smoking.26 UK research showed income as a significant contributor to health inequalities, and that obesity and smoking contribute significantly, but less profoundly, to income-related inequalities in health. Obesity and smoking were estimated to contribute 1.2% and 3.2% to inequality respectively. Despite the prevalence of smoking declining over time, its effects on inequalities have slightly increased because of its over-representation among the lowest socio-economic groups and its profound effects on health.27 Longitudinal research in the US, where Black adults also experience significant health disparities related to smoking and obesity, found that quitting smoking was associated with greater self-efficacy to eat low calorie foods.28 Another English study found that smoking is associated with greater absolute mortality risk for individuals in lower socioeconomic groups.29 In contrast, a large study of the English and Scottish populations found no indication of differential association by socioeconomic disadvantage between smoking and death from a range of smoking-related diseases.30

Authors of a study in Canada, Poland, and the US contended that eliminating smoking would halve the social gradient in mortality among men.31 In France, researchers estimated that 28% of the excess cancer cases in the four most deprived quintiles in men and 43% in women could be prevented if smoking in these four quintiles was similar to that of the least deprived quintile.32 In the Nordic countries, it has been estimated that about 40%-70% of the between-country differences in life expectancy can be attributed to smoking and alcohol.33 A major report from the National Cancer Institute concluded that among socioeconomic status indicators, the evidence is strongest for an association between adult educational attainment and tobacco-related cancer.34

In New Zealand, between 1996 and 1999, it was estimated that smoking contributed 21% to the gap between men aged 45–74 years with post-school qualifications and those with none. The corresponding figure for women was 11%.35 But other work suggested that only 5–10% of the larger inequality in mortality between Māori and non-Māori individuals was due to smoking, despite large differences in smoking prevalence.36 This estimate contrasted with a much greater estimated contribution by the Ministry of Health.37 Results from a more recent study tested the scenario of a hypothetical tobacco-free New Zealand, and found that it lowered mortality for all groups and resulted in an estimated 12.2% and 21.2% reduction in the absolute mortality gap between Māori and Europeans in 2006–2011, for males and females, respectively. It concluded that eliminating tobacco would notably reduce ethnic inequalities in absolute but not relative mortality.38 A study published in 2020 found that between 2013 and 2015 an estimated 13% of all deaths were caused by smoking in New Zealand. Nearly one in four (23%) deaths among Māori were attributable to smoking and nearly one in seven (14%) among Pacific people. Among non-Māori/non-Pacific people, one in eight (12%) deaths were attributable to smoking. These higher rates of smoking attributable mortality were responsible for 2.1 years of the life expectancy gap in Māori men, 2.3 years in Māori women, 1.4 years in Pacific men and 0.3 years among Pacific women.39

It is likely that indirect estimates of the contribution of tobacco smoking14, 26, 31 overestimate the importance of smoking by failing to take account of higher-than-average prevalence of behavioural and other risk factors in low-SES populations. Direct methods,35 however, may underestimate the importance of smoking because they do not take into account the long-term impact of smoking during pregnancy and the impact of smoking and exposure to tobacco smoke on diseases other than the ones for which epidemiological data are readily available. They also may not take account of the effects of spending on tobacco products on financial security and intergenerational poverty, which may help to perpetuate continuing high smoking rates in the children of smokers. These issues are explored further in Sections 9.4 to 9.8.

9.3.6 Are tobacco-related differentials in health status widening?

In the US, the socio-economic gap in life expectancy appears to be worsening. In people who had more than 12 years of education, life expectancy in the 1990s was about a year and a half greater than it was in the 1980s. In less educated people, life expectancy increased by only half a year. Much of the growing mortality gap can be attributed to the higher levels of decline in smoking-related diseases such as lung cancer and chronic obstructive pulmonary disease in more advantaged groups.40 Great disparities among socio-economic and racial groups exist for tobacco-related cancer incidences and mortality in the US, as well as access to, and quality of, cancer treatment.41 One paper has estimated that smoking will further widen socioeconomic disparities in all-cause mortality in the US until at least 2045 for men and even later for women.16

A Danish study concluded that the main explanations for the increase in social inequality in mortality since the mid-1980s are smoking (particularly among women) and alcohol use (particularly among men).42 Researchers in Europe looked at mortality data in 14 European countries from 1990 to 2004. Findings showed that over time, absolute increases in smoking attributable mortality rates generally declined among men, while among women, rates increased in most countries. Relative inequalities tended to increase in most countries, especially among men.14 Another European study looking at trends of smoking-attributable mortality found there was generally decreasing smoking-attributable mortality trends in consecutive birth cohorts among both low- and high-educated men and among high-educated women, but increasing smoking-attributable mortality among low-educated women. It concludes that in the future, smoking might become less important among men, but more important among women, as a driver of inequalities in mortality.43

In Australia, there is some evidence that socioeconomic disparities in morbidity and mortality from tobacco-related disease have widened over time. Although rates of heart attack, stroke, and deaths from cardiovascular disease are declining overall, in some instances socioeconomic inequalities are widening. Among women, inequalities in heart attack incidence appear to have widened between 2006 and 2016, and while cardiovascular disease death rates have declined for both men and women in all socioeconomic areas since 2001, there have been greater falls for men in higher socioeconomic areas, leading to widening inequalities. There is also evidence of growing inequalities in diabetes mortality between socioeconomic areas among both men and women. While inequalities in the prevalence of kidney disease narrowed slightly between 2011 and 2016, inequalities in mortality increased.44

 

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References

 

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41. Irvin Vidrine J, Reitzel LR, and Wetter DW. The role of tobacco in cancer health disparities. Curr Oncol Rep, 2009; 11(6):475–81. Available from: https://www.ncbi.nlm.nih.gov/pubmed/19840525

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43. Long D, Mackenbach J, Martikainen P, Lundberg O, Bronnum-Hansen H, et al. Smoking and inequalities in mortality in 11 European countries: A birth cohort analysis. Popul Health Metr, 2021; 19(1):3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/33516235

44. Australian Institute of Health and Welfare. Indicators of socioeconomic inequalities in cardiovascular disease, diabetes and chronic kidney disease. Canberra 2019. Available from: https://www.aihw.gov.au/reports/social-determinants/indicators-socioeconomic-inequalities/summary.