Health Inequality Remains Among Deprived Populations

Robert W. Aldridge, PhD

In high-income countries, those in excluded populations, such as those with substance abuse disorders, the homeless, sex workers, and the imprisoned have been shown to face extreme health inequality for a range of conditions, including infectious diseases, mental and behavioral disorders, cardiovascular conditions, and respiratory conditions.

When comparing mortality rates for those aged 15-64 years in the most and least socially deprived areas of England and Wales, the most deprived areas have a rate of mortality that is 2.8 times higher for males and 2.1 times higher for females.

“Our study highlights an extreme health inequity that persists in high-income countries,” lead author Robert W. Aldridge, PhD, of the Centre for Public Health Data Science at the Institute of Health Informatics at University College London, and colleagues wrote. “An inclusion health policy response must build on the evidence regarding who is at risk and the events that trigger exclusion to highlight the social and economic benefits of sustained action to prevent social exclusion.”

Standardized mortality rates (SMRs) were consistently higher for females than males, and of the 4 populations considered, sex workers were the least represented, prompting the research team to advise further research into that population as a priority.

“These populations often have multiple overlapping risk factors and extreme levels of morbidity and mortality. We identified numerous interventions to improve physical and mental health, and substance use; however, [the] evidence is scarce for structural interventions, including housing, employment, and legal support that can prevent exclusion and promote recovery,” Serena Luchenski, MSc, FFPH, et. al. wrote in an editorial accompanying the study.

Serena Luchenski, MSc, FFPH

The systematic review and meta-analysis examined data from MEDLINE, Embase, and the Cochrane Library from January 1, 2005, to October 1, 2015, that included morbidity (prevalence or incidence) and mortality (SMRs and mortality rates). In total, the data included 337 studies and 2835 data points— 698 from the US, 460 from Australia, 309 from Sweden, 257 from Canada, and 234 from the UK.

All-cause SMRs were found to be 11.86 in females (95% CI, 10.42—13.30; I² = 98.1%) and 7.88 in men (95%CI, 7.03—8.74; I² = 99.1%). All-cause SMRs were significantly increased in 99% (n = 91) of the 92 obtained data points. Summarized SMR estimates were highest for deaths due to injury, poisoning, and other external causes in both men (SMR, 7.89; 95% CI, 6.40—9.37; I² = 98.1%) and women (SMR, 18.72; 95% CI, 13.73—23.71; I² = 91.5%).

“To put it less colorfully, the causes of excess morbidity and mortality in socially excluded populations (ie, the social determinants of health) are not so much different from the causes of health inequalities more generally but differ in their degree,” Sir Michael Marmot, MBBS, MPH, PhD, FMedSci, FRCP, wrote in an accompanying comment. “Multiple intersecting causes and multiple forms of morbidity characterize social exclusion. The result is people with little hope or prospects and considerably shortened lives. The challenge is to bring socially excluded populations in from the cold—literally and metaphorically—and to provide them with the opportunity to be part of a diverse and flourishing society. The concerned practitioner might despair at achieving such social inclusion.”

Populations with substance use disorders were the most studied subgroup, totaling 42.1% (n = 1193) of the data points, followed by prisoners with 27.1% (n =769), homeless populations with 26.6% (n = 754), and sex workers with 4.2% (n = 119).

Infectious disease and mental/behavioral disorders were the most represented International Classification of Diseases (ICD-10) categories, accounting for 31.6% (n = 898) and 25.2% (n = 715) of the data points, respectively.

“Dedicated resources and better collaboration with the affected populations are needed to realize the benefits of existing interventions,” Luchenski and colleagues wrote. “Research must inform the benefits of early intervention and implementation of policies to address the upstream causes of exclusion, such as adverse childhood experiences and poverty.”

In regard to infectious disease, SMRs were increased in both sexes by 11.43 times (95% CI, 6.91—15.94; I² = 97.0%). The highest increase was in females by 5.58 times (95% CI, 1.46—9.70; I² = 60.0%) and then males by 2.93 times (95% CI, 1.61—4.05; I² = 65.4%). Disease prevalence was considered heterogeneous but high, with rates of hepatitis C virus ranging from 0.1% to 90%, rates of HIV from 0% to 54%, hepatitis B virus from 2% to 65%, and tuberculosis from 1% to 51%.

Sir Michael Marmot, MBBS, MPH, PhD, FMedSci, FRCP

Mental and behavioral disorder data for males and females were only available from prison populations, and data for both sexes was only available for those with substance abuse disorders. The prevalence of major depression in the prison population ranges from 3% in the month prior to assessment to 53% across their lifetime. Schizophrenia prevalence ranged from 0.9% to 4%, and bipolar disorder ranged from 0% to 45%.

“A welcome feature of the inclusion health approach advocated by Luchenski and colleagues is user involvement, which aims to enable people to improve their own health,” Marmot wrote. “We need the involvement of society as a whole to tackle the causes of the causes of social exclusion and its dramatic health consequences. This approach might save money and it is the right thing to do.”

The study, “Morbidity and mortality in homeless individuals, prisoners, sex workers, and individuals with substance use disorders in high-income countries: a systematic review and meta-analysis,” was published in The Lancet.

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