Are there non-linear relationships between alcohol consumption and long-term health?: A systematic review of observational studies employing approaches to improve causal inference

Abstract

Research has long found ‘J-shaped’ relationships between alcohol consumption and certain health outcomes, indicating a protective effect of moderate consumption. However, methodological limitations in most studies hinder causal inference. This review aimed to identify all observational studies employing improved approaches to mitigate confounding in characterizing alcohol–long-term health relationships, and to qualitatively synthesize their findings (PROSPERO registration: CRD42020185861). Eligible studies met the above description, were longitudinal (with pre-defined exceptions), discretized alcohol consumption, and were conducted with human populations. MEDLINE, PsycINFO, Embase and SCOPUS were searched in May 2020, yielding 16 published manuscripts reporting on cancer, diabetes, dementia, mental health, cardiovascular health, mortality, HIV seroconversion, and musculoskeletal health. Risk of bias of cohort studies was evaluated using the Newcastle Ottawa Scale, and a recently developed tool was used for Mendelian Randomization studies. A variety of functional forms were found, including reverse J/J-shaped relationships for prostate cancer and related mortality, dementia risk, mental health, and certain lipids. However, most outcomes were only evaluated by a single study, and few studies provided information on the role of alcohol consumption pattern. More research employing enhanced causal inference methods is urgently required to accurately characterize alcohol–long term health relationships.

Tools for assessing quality and risk of bias in Mendelian randomization studies: a systematic review

“…Of the 11 protocols describing use of a structured tool, Ibrahim 84 and Verdiesen 85 planned to use STROBE-MR 32 , 33 and other published literature, including the MR guidelines by Davies, 21 LS Lee 26 planned to use a self-developed questionnaire (also included in our synthesis of tools) based on published guidelines including Davies, 21 Grover 27 and Burgess. 20 Markozannes 99 planned to use a self-developed tool based on the results of the main analysis and of the sensitivity analysis; Naassila 100–102 planned to use Q-GENIE; 25 Shi 105 , 106 planned to use a modified version of a recently developed tool (no reference provided); Visontay 112 , 113 planned to use the tool developed by Mamluk; 28 and Wong 115 planned to conduct risk-of-bias assessment based on the guidelines from Davies. 21 Of the seven protocols describing a MR-specific risk-of-bias/quality-of-evidence assessment without using a structured tool, four planned an assessment based on the literature: Grover, 80 , 81 Jiang 86 and van Oort 111 referred to the MR methods protocol published by Grover 27 and Julian 87 did not report any reference.…”

Moderate Alcohol Consumption and Depression: A Marginal Structural Model Approach Promoting Causal Inference

“…This approach can address many of the limitations of conventional cohort studies (see Table S1 in the online supplement). Our recent review identified a single study applying MSMs to the alcohol-depression relationship (24). In a sample aged 20-64, Gemes et al found a U -shaped relationship with major depression after 7-9 years of follow-up (25).…”

A comprehensive evaluation of the longitudinal association between alcohol consumption and inflammation: Multiverse and vibration of effects analyses

“…8,9 Harmful drinking is responsible for substantial disease burden globally, 10 and there is evidence that inflammation may mediate the increased risk heavy drinking brings for a range of health outcomes. 11 However, as is the case for many conditions to which alcohol consumption is thought to contribute pathophysiologically, 12 some research suggests that compared to abstaining, lower levels of drinking may actually be beneficial when it comes to inflammation. [13][14][15][16][17] This is typically indexed via levels of inflammatory markers such as high-sensitivity C-reactive protein (hsCRP) -widely used by the clinical and research communities due to its stable expression in response to elevated proinflammatory cytokines.…”