9.3 Contribution of smoking to health inequality

Last updated: December 2016 

Suggested citation: Greenhalgh, EM, Scollo, MM, & Pearce, M. 9.3 Contribution of smoking to health inequality. In Scollo, MM and Winstanley, MH [editors]. Tobacco in Australia: Facts and issues. Melbourne: Cancer Council Victoria; 2016. 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 socio-economic status (SES) groups.1-3 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.3

People who are disadvantaged are more likely to live with multiple risks to their health. Lower socio-economic status is associated with higher rates of obesity, lack of adequate physical activity, and diabetes—especially so among Indigenous communities.1, 3, 4

There is also a clear social gradient among people who smoke, with lower education and income linked with higher rates of smoking (see Section 1.7). Social differentials in smoking during pregnancy, cigarette consumption, duration of smoking, and exposure to environmental tobacco smoke contribute substantially to socio-economic differentials in health status 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.5, 6

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, reported health status and smoking

People who live in disadvantaged areas are much less likely to assess their own health as excellent or good.3

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.3

In 2013, only 41% of smokers participating in the National Drug Strategy Household Survey reported their overall health as ‘very good’ or ‘excellent’, compared to 53% of ex-smokers and 61% of non-smokers. Ex-smokers were more likely to report heart disease, diabetes, and cancer than smokers and non-smokers. Smokers were more likely to report asthma and mental illness.3

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 2014–15, 15% of people in the most disadvantaged group reported having three or more chronic diseases, compared with 6% of the most advantaged. Smoking-related diseases such as chronic obstructive pulmonary disease, asthma, cancer, and cardiovascular disease are all experienced at higher rates by lower socioeconomic groups.7 Chronic kidney disease is also more common in low socio-economic groups, and particularly so among Indigenous Australians.3, 8

The Australian Institute of Health and Welfare has estimated that lung cancer was the fourth leading cause of disease among men and the seventh leading cause of disease among women in 2011. Lung cancer incidence is disproportionately high in those of lower socio-economic status in Australia, with increasing incidence of lung cancer associated with decreasing socio-economic status, across the five years 2003–2007. In the year 2008–09, the rate of hospitalisations for lung cancer was higher for those living in the lowest socio-economic areas of Australia. Those living in the lowest socio-economic areas were hospitalised for lung cancer at 1.5 times the rate of those living in areas of highest socio-economic advantage.9

The worsening of asthma symptoms is associated with active smoking and/or exposure to secondhand smoke. Smoking and asthma are both more common in those living in low socio-economic areas. The Australian Centre for Asthma Monitoring (a collaborating unit of the Australian Institute of Health and Welfare) reported that in 2007–08, not only was asthma much more common among those living in the most deprived socio-economic areas in Australia, but that rates of smoking among asthmatics in low socio-economic areas were far higher than for asthmatic smokers living in areas of higher socio-economic status (37.8% and 12.9% respectively). The disparity between the lowest and highest socio-economic group in asthma prevalence was found to have widened between survey years 2004–05 and 2007–08.10 In 2014–15, 13% of the most disadvantaged Australians reported having asthma, compared with 10% of the most advantaged.7

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.3 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 among the disadvantaged. 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 2009–11, mortality rates were 1.3 times as high for the lowest SES areas compared to highest SES areas for males, 1.2 times as high for females, and 1.3 for both sexes combined. The leading cause of death among all groups was coronary heart disease, and rates increased with increasing disadvantage. For most leading causes of death, rates increased with lower socio-economic status. Among the most disadvantaged group, rates of deaths from COPD and diabetes were about twice that of the most advantaged, and about 1.5 times greater for lung cancer.11 There were also higher asthma mortality rates among those residing in areas of lowest socioeconomic status, particularly among people aged 5–34, who were four times as likely to die from asthma compares to people living in areas of highest socioeconomic status.12

International research has shown similar trends. A 24-year study of British men and women examined the relationship between socio-economic status and mortality, and the influence smoking, alcohol consumption, diet and physical activity have on mortality. In terms of all-cause mortality, those of lowest socio-economic position had 1.6 times the risk of death in comparison to those of higher socio-economic position. There was also a graded association for cardiovascular disease mortality and socio-economic position. Health risk behaviours, including smoking, were connected with mortality.13

Research in other European countries,14-16 and the US,17 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 socio-economic position, as well as ethnicity.18, 19

9.3.4 Socio-economic disparities in health-adjusted life expectancy

The AIHW’s latest burden of disease report shows that in 2011, a total of 4,494,000 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. Table 9.3.1 shows the DALYs for each of the five socio-economic quintiles in 2011.

Table 9.3.1
Disability-adjusted life years lost, Australia, by socio-economic quintile, Australia, 2011

Source: Australian Institute of Health and Welfare, Table 8.820
DALY = disability-adjusted life year

After adjusting for age, rates of DALYs were 1.5 times higher in the lowest SES quintile than in the highest. There was a clear association between increasing rate of burden from coronary heart disease, lung cancer, suicide and self-inflicted injuries, COPD, and stroke with decreasing socioeconomic position. 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 1.7 times higher, among the most disadvantaged group compared with the least. Rates of burden were 1.7 times higher in very remote areas than in major cities.20

Tobacco use was the most burdensome behavioural risk factor, with nine per cent of the total burden attributable to smoking. Tobacco use was responsible for 80% of lung cancer DALY, 75% of the COPD DALY, about half of the total burden of oesophageal cancer (54%) and nearly half of the mouth and pharyngeal cancer (46%) burden.20

Life expectancy among Indigenous Australians 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.21

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.22

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 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.23 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.24

Authors of a study in Canada, Poland, and the US contended that eliminating smoking would halve the social gradient in mortality among men.25 Some public health experts been critical of these sorts of estimates, because some estimates have been derived by using lung cancer mortality as a proxy measure for smoking exposure, rather than using crude estimates to determine the contribution of smoking to socio-economic differences in mortality; hence they are likely to overestimate the importance of smoking.26 Authors of such studies have generally acknowledged the limits of indirect estimation.

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%.27 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.28 This estimate contrasted with a much greater estimated contribution by the Ministry of Health.29

The Australian Burden of Disease study estimated that a 21% reduction of burden could be achieved if all of the five socioeconomic groups experienced the same disease burden as the highest group.20 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.30 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.

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.31

It is likely that indirect estimates of the contribution of tobacco smoking16, 24, 25 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,27 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.32 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.33

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).34 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.16

The situation for Australia is much less clear-cut.

A study published by the Australian Institute of Health and Welfare in 2006 indicated that death rates for cardiovascular disease reduced in all socio-economic groups between 1999 and 2003. There was a decrease in the size of the gap between the rates of death between upper and lower socio-economic groups for coronary heart disease and cardiovascular disease as a whole but an increase in the relative effect of disadvantage (the proportion by which the lowest socio-economic group was higher than the highest socio-economic group) for coronary heart disease, stroke and cardiovascular disease as a whole.35 Between 1981 and 2011, overall death rates from cardiovascular disease declined. However, in 2011, those of lower socio-economic status, the Indigenous and those living in remote areas of Australia still had the highest rates of hospitalisations and death from cardiovascular disease.36

Mortality rates from cancer show a clear social gradient. For the period 2009–2012, those living in the most disadvantaged areas had the highest mortality rate for all cancers combined, and also for smoking-related cancers such as lung, pancreatic, kidney, bladder, and bowel.37 In 2009–11, lung cancer death rates were 1.6 times as high in the lowest socioeconomic group compared with the highest.11 No data could be located on whether or not disparities in lung cancer mortality have widened.

Between 1979 and 2006, mortality rates between low-SES groups and high-SES groups narrowed in absolute terms among females for ischaemic heart disease (27 to 23 per 100,000). However, absolute differences for ischaemic heart disease widened in males across this period (52 to 63 per 100,000). Absolute differences for stroke between low and high-SES groups declined in males and females (16 to 13 per 100,000 among males and 13 to 7 per 100,000 among females). However relative declines were greater in high socio-economic groups compared to low socio-economic groups for both ischaemic heart disease (28% average five yearly decline in high socio-economic status males compared with 21% in low-SES males, and 30% and 21% for females respectively). For stroke, there was a 25% average five yearly decline in high-SES males compared to 21% in low-SES status males; 26% and 23% for females respectively).38

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