Published 14 July 2009, doi:10.1136/bmj.b2515
Cite this as: BMJ 2009;339:b2515

Editorials

Why has mortality from coronary heart disease in young adults levelled off?

Social inequalities must be tackled, as well as risk factors

In the linked study (doi:10.1136/bmj.b2613), O’Flaherty and colleagues examine trends in mortality from coronary heart disease in Scotland according to age and deprivation, from 1986 to 2006.¹ The study adds to these authors’ previous work on the role of risk factors and advances in medical care in explaining the decline of mortality from coronary heart disease in several countries. The study shows that mortality from this disease has flattened in younger adults (age 35-54) in the most socially deprived groups. This work shows how changes in population levels of traditional risk factors have led to the impressive decline in mortality from coronary heart disease in recent decades.²

Mortality has fallen and age standardised rates are down in all social groups. This is good news, but, on the negative side, the favourable trends are flattening in younger men and perhaps women, although the authors caution not to overstate the importance of these changes. This is an example of the usefulness of examining age specific rates before naively applying age standardisation. A similar levelling of mortality from coronary heart disease in younger people has been seen in other developed countries such as Australia³ and the United States.⁴ When O’Flaherty and colleagues examined age specific mortality by deprivation score, they found that mortality was decreasing at all ages in almost all social groups. They also found that relative inequalities were reasonably flat but absolute inequalities decreased in most age groups in men and women, although they do not present data on changes in absolute inequality.¹ What is most worrying is that the slowing of improvements at younger ages is confined to the most deprived groups of young men and women, as has been reported elsewhere.^{5 6} Why are the most deprived young adults in Scotland not sharing the benefits seen by others?

Risk factors for coronary heart disease follow strong social patterns, and differential changes in risk factors are a plausible explanation. Yet the evidence does not seem to support this argument. Although at a national level improvements in many risk factors (cholesterol, body mass index, blood pressure, diet, physical activity, and smoking) in England corresponded to an overall decline in mortality from coronary heart disease, slight changes in the prevalence of risk factors leading to a less marked social gradient did not tally with an increase in inequalities in mortality.⁷ A similar decoupling of traditional risk factors (total serum cholesterol, hypertension, and smoking) from mortality for cardiovascular disease was seen in Finland, where declining mortality in different social groups can no longer be explained by changes in risk factors, with changes in risk factors underestimating the extent of this decline.⁸ Possible reasons for the lack of correspondence between the two include uncertainty about the time lag between changes in risk factors and changes in mortality or social patterns in the use of secondary prevention and invasive cardiac procedures.

But coronary heart disease is not the only cause of death to show changing patterns over recent years. In Scotland the decline in mortality in men under 60 slowed down in the 1990s, with overall death rates starting to increase in men aged 15-44.⁹ Such changes may reflect slowing declines in death from cardiovascular disease but have largely been driven by increases in suicide and mortality associated with the use of alcohol and drugs. Socioeconomic inequalities in mortality have increased for many causes other than cardiovascular disease in both sexes,^{10 11} and these causes do not share the same risk factors. So any change in cardiovascular risk factors responsible for increasing inequalities in mortality from coronary heart disease must have been accompanied by similar changes in risk factors for other causes of death.

Another possible explanation for changes in the patterning of social inequalities is that the axis of inequality itself has changed. In O’Flaherty and colleagues’ study, which uses an area based measure of deprivation, this could result from increasing polarisation (where the more deprived areas contain a greater concentration of deprived people, possibly because of selective migration) or increasing absolute differentials (the poor becoming poorer).¹ For an individual measure such as education the meaning or quality of different lengths of education may have changed over time.¹⁰

O’Flaherty and colleagues’ study indicates that the levelling of mortality from coronary heart disease in young adults cannot be tackled without improving social inequalities. It may be that this can be achieved solely through modifying risk factors; although the link between risk factors and cardiovascular mortality has weakened, it still seems to be stronger for lower socioeconomic groups.⁸ However, deliberate interventions to reduce inequalities in health through modification of major risk factors have had limited success to date. The alternative is to tackle the social inequalities themselves—unequal distribution of power, money, resources, and life chances.¹² Although not a quick fix solution, if it works then policies to reduce social inequalities will ultimately reduce inequalities in health associated with all causes that manifest as social gradients and not just coronary heart disease.

Cite this as: BMJ 2009;339:b2515

¹ MRC Social and Public Health Sciences Unit, Glasgow G12 8RZ, ² Division of Health Sciences, University of South Australia, Adelaide SA 5001, Australia

Research, doi:10.1136/bmj.b2613

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Competing interests: None declared.

Provenance and peer review: Commissioned; not externally peer reviewed.

References

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2. Unal B, Critchley JA, Capewell S. Small changes in United Kingdom cardiovascular risk factors could halve coronary heart disease mortality. J Clin Epidemiol 2005;58:733-40.[CrossRef][Web of Science][Medline]
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5. Mackenbach JP, Bos V, Andersen O, Cardano M, Costa G, Harding S, et al. Widening socioeconomic inequalities in mortality in six Western European countries. Int J Epidemiol 2003;32:830-7.[Abstract/Free Full Text]
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8. Harald K, Koskinen S, Jousilahti P, Torppa J, Vartiainen E, Salomaa V. Changes in traditional risk factors no longer explain time trends in cardiovascular mortality and its socioeconomic differences. J Epidemiol Commun Health 2008;62:251-7.[Abstract/Free Full Text]
9. McLoone P. Increasing mortality among adults in Scotland 1981 to 1999. Eur J Public Health 2003;13:230-4.[Abstract/Free Full Text]
10. Jemal A, Ward E, Anderson RN, Murray T, Thun MJ. Widening of socioeconomic inequalities in US death rates, 1993-2001. PLoS ONE 2008;3:e2181.[CrossRef][Medline]
11. Leyland AH, Dundas R, McLoone P, Boddy FA. Cause-specific inequalities in mortality in Scotland: two decades of change. A population-based study. BMC Public Health 2007;7:172.[CrossRef][Medline]
12. Commission on Social Determinants of Health. Closing the gap in a generation: health equity through action on the social determinants of health. Final report. Geneva: WHO, 2008. http://whqlibdoc.who.int/publications/2008/9789241563703_eng.pdf.

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Coronary heart disease mortality among young adults in Scotland in relation to social inequalities: time trend study

Martin O’Flaherty, Jennifer Bishop, Adam Redpath, Terry McLaughlin, David Murphy, James Chalmers, and Simon Capewell
BMJ 2009 339: b2613. [Abstract] [Full Text] [PDF]

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