The dose-response relationship between socioeconomic deprivation and alcohol-attributable mortality risk—a systematic review and meta-analysis

Background Individuals with low socioeconomic status (SES) experience a higher risk of mortality, in general, and alcohol-attributable mortality in particular. However, a knowledge gap exists concerning the dose-response relationships between the level of socioeconomic deprivation and the alcohol-attributable mortality risk. Methods We conducted a systematic literature search in August of 2020 to update a previous systematic review that included studies published up until February of 2013. Quantitative studies reporting on socioeconomic inequality in alcohol-attributable mortality among the general adult population were included. We used random-effects dose-response meta-analyses to investigate the relationship between the level of socioeconomic deprivation and the relative alcohol-attributable risk (RR), by sex and indicator of SES (education, income, and occupation). Results We identified 25 eligible studies, comprising about 241 million women and 230 million men, among whom there were about 75,200 and 308,400 alcohol-attributable deaths, respectively. A dose-response relationship between the level of socioeconomic deprivation and the RR was found for all indicators of SES. The sharpest and non-linear increase in the RR of dying from an alcohol-attributable cause of death with increasing levels of socioeconomic deprivation was observed for education, where, compared to the most educated individuals, individuals at percentiles with decreasing education had the following RR of dying: women: 25th: 2.09 [95% CI 1.70–2.59], 50th: 3.43 [2.67–4.49], 75th: 4.43 [3.62–5.50], 100th: 4.50 [3.26–6.40]; men: 25th: 2.34 [1.98–2.76], 50th: 4.22 [3.38–5.24], 75th: 5.87 [4.75–7.10], 100th: 6.28 [4.89–8.07]. Conclusions The findings of this study show that individuals along the entire continuum of SES are exposed to increased alcohol-attributable mortality risk. Differences in the dose-response relationship can guide priorities in targeting public health initiatives. Supplementary Information The online version contains supplementary material available at 10.1186/s12916-021-02132-z.


Rationale
3 Describe the rationale for the review in the context of what is already known. 4-5 Objectives 4 Provide an explicit statement of questions being addressed with reference to participants, interventions, comparisons, outcomes, and study design (PICOS).

Protocol and registration 5
Indicate if a review protocol exists, if and where it can be accessed (e.g., Web address), and, if available, provide registration information including registration number.
6 Eligibility criteria 6 Specify study characteristics (e.g., PICOS, length of follow-up) and report characteristics (e.g., years considered, language, publication status) used as criteria for eligibility, giving rationale.

6, Table S2
Information sources 7 Describe all information sources (e.g., databases with dates of coverage, contact with study authors to identify additional studies) in the search and date last searched.

6
Search 8 Present full electronic search strategy for at least one database, including any limits used, such that it could be repeated.
6, see PROSPERO protocol for complete search terms Study selection 9 State the process for selecting studies (i.e., screening, eligibility, included in systematic review, and, if applicable, included in the meta-analysis).
6 Data collection process 10 Describe method of data extraction from reports (e.g., piloted forms, independently, in duplicate) and any processes for obtaining and confirming data from investigators.
6 Data items 11 List and define all variables for which data were sought (e.g., PICOS, funding sources) and any assumptions and simplifications made.

7
Risk of bias in individual studies 12 Describe methods used for assessing risk of bias of individual studies (including specification of whether this was done at the study or outcome level), and how this information is to be used in any data synthesis. 7, Table S3 3

Study selection
17 Give numbers of studies screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally with a flow diagram.
10-11 Fig. 1 Study characteristics 18 For each study, present characteristics for which data were extracted (e.g., study size, PICOS, followup period) and provide the citations. Table 1 Risk of bias within studies 19 Present data on risk of bias of each study and, if available, any outcome level assessment (see item 12). Results of individual studies 20 For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group (b) effect estimates and confidence intervals, ideally with a forest plot.

Summary of evidence
24 Summarize the main findings including the strength of evidence for each main outcome; consider their relevance to key groups (e.g., healthcare providers, users, and policy makers).

14-15
Limitations 25 Discuss limitations at study and outcome level (e.g., risk of bias), and at review-level (e.g., incomplete retrieval of identified research, reporting bias).       0=Satisfactory, criterion is met (e.g., sample is representative; data were linked etc.) 0a=Classification via a previous census 0b=Classification via another family member 0c=Formation of a rest category 0d=One or more pairwise comparisons are not reported 1=Not satisfactory, criterion is not met 1a=Diseases of liver and/or pancreas are included 1b=Neoplasms of the upper gastrointestinal tract are included 1c=Injuries of all kind are included 1d=The age ranged spanned less than 10 years 2=More than one of the disease categories mentioned above are included Models were fit to the level of socioeconomic deprivation, scaled as a proportion between 0 and 1. The coefficients for the level of socioeconomic deprivation refer to the difference between the lowest level of socioeconomic deprivation (i.e., lowest percentile) and the highest level of socioeconomic deprivation (100 th percentile).
Note. The level of socioeconomic deprivation, the indicator of SES used, and sex were introduced as covariates in three stepwise models. Fixed effects for the study ID were used to control for clustering of observations within studies. for the level of socioeconomic deprivation refer to the difference between the lowest level of deprivation (i.e., lowest percentile) and the highest level of socioeconomic deprivation (100 th percentile).
Note. Fixed effects for the study ID were used to control for clustering of observations within studies. Note. Models were fit to the level of socioeconomic deprivation, scaled as a proportion between 0 and 1. The coefficients for the level of socioeconomic deprivation refer to the difference between the lowest level of socioeconomic deprivation (i.e., lowest percentile) and the highest level of socioeconomic deprivation (100 th percentile).