Investigating the association between income inequality in youth and deaths of despair in Canada: a population-based cohort study from 2006 to 2019

Income inequality and deaths of despair risk in Canada, identifying possible mechanisms

BACKGROUND

Declines in life expectancy in developed countries have been attributed to increases in drug-related overdose, suicide, and liver cirrhosis, collectively referred to as deaths of despair. Income inequality is proposed to be partly responsible for increases in deaths of despair rates. This study investigated the associations between income inequality, deaths of despair risk in Canada, and potential mechanisms (stress, social cohesion, and access to health services).

METHODS

We obtained data from the Canadian Community Health Survey and the Canadian Vital Statistics Database from 2007 to 2017. A total of 504,825 Canadians were included in the analyses. We used multilevel survival analyses, as measured by the Gini coefficient, to examine the relationships between income inequality and mortality attributed to drug overdose, suicide, death of despair, and all-cause. We then used multilevel path analyses to investigate whether each mediator (stress, social cohesion, and access to mental health professionals), which were investigated using separate mediation models, influenced the relationship between income inequality and drug overdose, suicide, deaths of despair, and all-cause death.

RESULTS

Adjusted multilevel survival analyses demonstrated significant relationships between a one-SD increase in Gini coefficient was associated with an increased hazard for drug overdose (HRadj. = 1.28; 95 CI = 1.05, 1.55), suicide (HRadj. = 1.24; 95 CI = 1.06, 1.46), deaths of despair (HRadj. = 1.26; 95 CI = 1.12, 1.40), and all-cause death (HRadj. = 1.04; 95 CI = 1.02, 1.07). Adjusted path analyses indicated that stress, social cohesion, and access to mental health professionals significantly mediated the association between income inequality and mortality outcomes.

CONCLUSION

Income inequality is associated with deaths of despair and this relationship is mediated by stress, social cohesion, and access to mental health professionals. Findings should be applied to develop programs to address income inequality in Canada.

Causal Assessment of Income Inequality on Self-Rated Health and All-Cause Mortality: A Systematic Review and Meta-Analysis

Policy Points Income is thought to impact a broad range of health outcomes. However, whether income inequality (how unequal the distribution of income is in a population) has an additional impact on health is extensively debated. Studies that use multilevel data, which have recently increased in popularity, are necessary to separate the contextual effects of income inequality on health from the effects of individual income on health. Our systematic review found only small associations between income inequality and poor self-rated health and all-cause mortality. The available evidence does not suggest causality, although it remains methodologically flawed and limited, with very few studies using natural experimental approaches or examining income inequality at the national level.

CONTEXT

Whether income inequality has a direct effect on health or is only associated because of the effect of individual income has long been debated. We aimed to understand the association between income inequality and self-rated health (SRH) and all-cause mortality (mortality) and assess if these relationships are likely to be causal.

METHODS

We searched Medline, ISI Web of Science, Embase, and EconLit (PROSPERO: CRD42021252791) for studies considering income inequality and SRH or mortality using multilevel data and adjusting for individual-level socioeconomic position. We calculated pooled odds ratios (ORs) for poor SRH and relative risk ratios (RRs) for mortality from random-effects meta-analyses. We critically appraised included studies using the Risk of Bias in Nonrandomized Studies - of Interventions tool. We assessed certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation framework and causality using Bradford Hill (BH) viewpoints.

FINDINGS

The primary meta-analyses included 2,916,576 participants in 38 cross-sectional studies assessing SRH and 10,727,470 participants in 14 cohort studies of mortality. Per 0.05-unit increase in the Gini coefficient, a measure of income inequality, the ORs and RRs (95% confidence intervals) for SRH and mortality were 1.06 (1.03-1.08) and 1.02 (1.00-1.04), respectively. A total of 63.2% of SRH and 50.0% of mortality studies were at serious risk of bias (RoB), resulting in very low and low certainty ratings, respectively. For SRH and mortality, we did not identify relevant evidence to assess the specificity or, for SRH only, the experiment BH viewpoints; evidence for strength of association and dose-response gradient was inconclusive because of the high RoB; we found evidence in support of temporality and plausibility.

CONCLUSIONS

Increased income inequality is only marginally associated with SRH and mortality, but the current evidence base is too methodologically limited to support a causal relationship. To address the gaps we identified, future research should focus on income inequality measured at the national level and addressing confounding with natural experiment approaches.

Risk factors for deaths of despair in England: An ecological study of local authority mortality data

Deaths of Despair (DoD) are socially patterned fatalities encompassing those attributable to drug and alcohol misuse and suicide. DoD occur much more frequently in socially deprived communities. This ecological study aimed to yield new knowledge on the spatial distribution of DoD, and socioeconomic factors that predict DoD risk in England. Via ICD-10 coding, deaths nationally during 2019-2021 were classified to non-overlapping categories of drug-related death, alcohol-specific death, and suicide. The proportion of DoD from each of these causes was calculated and age standardised DoD rates were generated for local authorities. A multivariable regression model for DoD risk was developed using 25 socioeconomic indicators. In 2019-2021, an estimated 46,200 people lost their lives due to DoD. Rates were higher in the North and in coastal areas (p < 0.001), ranging regionally from 25.1/100,000 (SD 6.3) in London to 54.7/100,000 (SD 9.5) in the North East. Alcohol-specific deaths were the largest contributor of DoD, accounting for 44.1% (95%CI 43.5-44.8%) of all such deaths. Living in the North, unemployment, White British ethnicity, living alone, economic inactivity, employment in elementary occupations, and living in urban areas were significantly associated with elevated DoD risk. DoD in England are spatially patterned, with northern regions experiencing a much higher burden of mortality from these avoidable causes. This study provides novel insights into the area-level factors associated with DoD in England. Potential ecological error is a key limitation.

Income inequality and 'hospitalisations of despair' in Canada: a study on longitudinal, population-based data

BACKGROUND

Rates of drug overdoses, alcohol-related liver disease and suicide attempts represent a major public health burden in Canada. While the existing literature does highlight some evidence of association between income inequality and mental health and deaths of despair, no existing research has investigated more intermediate events. As such, the objective of the current study is to investigate the association between income inequality and hospitalisations of despair over time.

METHODS

Data from the 2006 Canadian Census, the 2007/2008 Canadian Community Health Survey and the 2007-2018 Discharge Abstract Database were linked. Data were analysed using Cox proportional hazards modelling accounting for robust standard errors at the area level to investigate associations between income inequality at baseline and hazards for hospitalisations of despair, hospitalisations attributable to drug overdose, alcohol-related liver disease and suicide attempts, and all-cause hospitalisations, while controlling for sociodemographics characteristics (including income) and relevant area-level variables.

RESULTS

The results highlighted statistically significant associations between income inequality and hazard of hospitalisations of despair (HR 1.38, 95% CI 1.06 to 1.80), hospitalisations related to drug overdose (HR 1.51, 95% CI 1.07 to 2.13) and all-cause hospitalisations (HR 1.17, 95% CI 1.05 to 1.30). The association between income inequality and hospitalisations related to alcohol-related liver disease and suicide attempts/self-harm were not statistically significant.

CONCLUSION

Overall, the results showed evidence of associations between income inequality and hospitalisations of despair, drug overdose-related hospitalisations and all-cause hospitalisations. These findings are applicable to upstream policy discussion regarding reducing income inequality and identify potential points of intervention for prevention of drug overdose, alcohol-related liver disease and suicide attempts/self-harm.

Intervention targets for reducing mortality between mid-adolescence and mid-adulthood: a protocol for a machine-learning facilitated systematic umbrella review

INTRODUCTION

A rise in premature mortality-defined here as death during the most productive years of life, between adolescence and middle adulthood (15-60 years)-is contributing to stalling life expectancy in high-income countries. Causes of mortality vary, but often include substance misuse, suicide, unintentional injury and non-communicable disease. The development of evidence-informed policy frameworks to guide new approaches to prevention require knowledge of early targets for intervention, and interactions between higher level drivers. Here, we aim to: (1) identify systematic reviews with or without meta-analyses focused on intervention targets for premature mortality (in which intervention targets are causes of mortality that can, at least hypothetically, be modified to reduce risk); (2) evaluate the review quality and risk of bias; (3) compare and evaluate each review's, and their relevant primary studies, findings to identify existing evidence gaps.

METHODS AND ANALYSIS

In May 2023, we searched electronic databases (MEDLINE, PubMed, Embase, Cochrane Library) for peer-reviewed papers published in the English language in the 12 years from 2012 to 2023 that examined intervention targets for mortality. Screening will narrow these papers to focus on systematic reviews with or without meta-analyses, and their primary papers. Our outcome is death between ages 15 and 60 years; with potential intervention targets measured prior to death. A MeaSurement Tool to Assess systematic Reviews (AMSTAR 2) will be used to assess quality and risk of bias within included systematic reviews. Results will be synthesised narratively due to anticipated heterogeneity between reviews and between primary studies contained within included reviews.

ETHICS AND DISSEMINATION

This review will synthesise findings from published systematic reviews and meta-analyses, and their primary reviewed studies, meaning ethics committee approval is not required. Our findings will inform cross-cohort consortium development, be published in a peer-reviewed journal, and be presented at national and international conferences.

PROSPERO REGISTRATION NUMBER

CRD42022355861.