Background and objective: The obesity paradox is a well-established clinical conundrum in COPD patients. This study aimed to provide an updated analysis of the relationship between body mass index (BMI) and mortality in this population.Methods: A systematic search was conducted through Embase, PubMed, and Web of Science. International BMI cut-offs were employed to define underweight, overweight and obesity. The primary outcome was all-cause mortality, and the secondary outcome was respiratory and cardiovascular mortality.Results: 120 studies encompassed a total of 1 053 272 patients. Underweight status was associated with an increased risk of mortality, while overweight and obesity were linked to a reduced risk of mortality. A nonlinear U-shaped relationship was observed between BMI and all-cause mortality, respiratory mortality and cardiovascular mortality. Notably, an inflection point was identified at BMI 28.75 kg·m⁻²(relative risk 0.83, 95% CI 0.80–0.86), 30.25 kg·m⁻²(relative risk 0.51, 95% CI 0.40–0.65) and 27.5 kg·m⁻²(relative risk 0.76, 95% CI 0.64–0.91) for all-cause, respiratory and cardiovascular mortality, respectively, and beyond which the protective effect began to diminish.Conclusion: This study augments the existing body of evidence by confirming a U-shaped relationship between BMI and mortality in COPD patients. It underscores the heightened influence of BMI on respiratory and cardiovascular mortality compared to all-cause mortality. The protective effect of BMI was lost when BMI values exceeded 35.25 kg·m⁻², 35 kg·m⁻²and 31 kg·m⁻²for all-cause, respiratory and cardiovascular mortality, respectively.

Objective: This systematic review and meta-analysis aimed to evaluate whether dyslipidemia affects the mortality and severity of COVID-19, we also aimed to evaluate whether other comorbidities influence the association. Methods: A systematic literature search using PubMed, Embase, and EuropePMC was performed on 8 October 2020. This study’s main outcome is a poor composite outcome, comprising of mortality and severe COVID-19. Results: There were 9 studies with 3663 patients. The prevalence of dyslipidemia in this pooled analysis was 18% (4%-32%). Dyslipidemia was associated with increased composite poor outcome (RR 1.39 [1.02, 1.88], P = .010; I²: 56.7%, P = .018). Subgroup analysis showed that dyslipidemia was associated with severe COVID-19 (RR 1.39 [1.03, 1.87], P = .008; I²: 57.4%, P = .029). Meta-regression showed that the association between dyslipidemia and poor outcome varies by age (coefficient: −0.04, P = .033), male gender (coefficient: −0.03, P = .042), and hypertension (coefficient: −0.02, P = .033), but not diabetes (coefficient: −0.24, P = .135) and cardiovascular diseases (coefficient: −0.01, P = .506). Inverted funnel-plot was relatively symmetrical. Egger’s test indicates that the pooled analysis was not statistically significant for small-study effects ( P = .206). Conclusion: Dyslipidemia potentially increases mortality and severity of COVID-19. The association was stronger in patients with older age, male, and hypertension. PROSPERO Registration Number: CRD42020213491