METHODS: The data set analysed includes COVID-19 patients hospitalized between January 2020 and January 2022 in 52 countries. We investigated how symptoms on admission, co-morbidities, risk factors and treatments varied by age, sex and other characteristics. We used Cox regression models to investigate associations between demographics, symptoms, co-morbidities and other factors with risk of death, admission to an intensive care unit (ICU) and invasive mechanical ventilation (IMV).

RESULTS: Data were available for 689 572 patients with laboratory-confirmed (91.1%) or clinically diagnosed (8.9%) SARS-CoV-2 infection from 52 countries. Age [adjusted hazard ratio per 10 years 1.49 (95% CI 1.48, 1.49)] and male sex [1.23 (1.21, 1.24)] were associated with a higher risk of death. Rates of admission to an ICU and use of IMV increased with age up to age 60 years then dropped. Symptoms, co-morbidities and treatments varied by age and had varied associations with clinical outcomes. The case-fatality ratio varied by country partly due to differences in the clinical characteristics of recruited patients and was on average 21.5%.

OBJECTIVE: To investigate the association between smoking status or smoking cessation time and complications after cancer surgery.

DATA SOURCES: Embase, CINAHL, Medline COMPLETE, and Cochrane Library were systematically searched for studies published from January 1, 2000, to August 10, 2023.

STUDY SELECTION: Observational and interventional studies comparing the incidence of complications in patients undergoing cancer surgery who do and do not smoke.

DATA EXTRACTION AND SYNTHESIS: Two reviewers screened results and extracted data according to the Meta-Analyses of Observational Studies in Epidemiology (MOOSE) reporting guidelines. Data were pooled with a random-effects model and adjusted analysis was performed.

MAIN OUTCOMES AND MEASURES: The odds ratio (OR) of postoperative complications (of any type) for people who smoke currently vs in the past (4-week preoperative cutoff), currently smoked vs never smoked, and smoked within shorter (2-week cutoff) and longer (1-year cutoff) time frames.

RESULTS: The meta-analyses across 24 studies with a pooled sample of 39 499 participants indicated that smoking within 4 weeks preoperatively was associated with higher odds of postoperative complications compared with ceasing smoking for at least 4 weeks (OR, 1.31 [95% CI, 1.10-1.55]; n = 14 547 [17 studies]) and having never smoked (OR, 2.83 [95% CI, 2.06-3.88]; n = 9726 [14 studies]). Within the shorter term, there was no statistically significant difference in postoperative complications between people who had smoked within 2 weeks preoperatively and those who had stopped between 2 weeks and 3 months in postoperative complications (OR, 1.19 [95% CI, 0.89-1.59]; n = 5341 [10 studies]), although the odds of complications among people who smoked within a year of surgery were higher compared with those who had quit smoking for at least 1 year (OR, 1.13 [95% CI, 1.00-1.29]; N = 31 238 [13 studies]). The results from adjusted analyses were consistent with the key findings.