Daily Respiratory Research Analysis
Three high-impact studies advance respiratory medicine today: a US Veterans Affairs cohort links prior COVID-19 to increased 12‑month risk of diverse subsequent infections; a population-based Thorax cohort shows women are more susceptible than men to smoking-related COPD outcomes; and a CHEST study finds COPD patients have persistently higher long-term healthcare use after COVID-19, mitigated by ≥3 vaccinations.
Summary
Three high-impact studies advance respiratory medicine today: a US Veterans Affairs cohort links prior COVID-19 to increased 12‑month risk of diverse subsequent infections; a population-based Thorax cohort shows women are more susceptible than men to smoking-related COPD outcomes; and a CHEST study finds COPD patients have persistently higher long-term healthcare use after COVID-19, mitigated by ≥3 vaccinations.
Research Themes
- Post-COVID immune vulnerability and secondary infections
- Sex-specific susceptibility to smoking-related COPD
- Long-term healthcare utilization in COPD after COVID-19 and vaccine mitigation
Selected Articles
1. Rates of infection with other pathogens after a positive COVID-19 test versus a negative test in US veterans (November, 2021, to December, 2023): a retrospective cohort study.
In a spatiotemporally aligned VA cohort, COVID-19 positivity was associated with higher 12-month rates of diverse infections versus test-negative controls, including outpatient infectious diagnoses (RR 1.17), outpatient respiratory infections (RR 1.46), and hospitalizations for infectious illnesses (RR 1.41). Compared with influenza admissions, COVID-19 admissions had higher subsequent infection-related hospitalizations and sepsis. ≥3 vaccine doses attenuated long-term healthcare burden.
Impact: This is a large, methodologically rigorous analysis linking COVID-19 to increased risk of subsequent infections and sepsis, with direct implications for long COVID care and vaccination strategies.
Clinical Implications: Implement targeted surveillance and prevention for secondary infections in post-COVID patients, prioritize vaccination boosters (≥3 doses) for COPD and other high-risk groups, and consider enhanced sepsis vigilance in the year after infection.
Key Findings
- COVID-19 positivity increased outpatient infectious diagnoses (RR 1.17; 95% CI 1.15–1.19) and outpatient respiratory infections (RR 1.46; 95% CI 1.43–1.50) versus test-negative controls.
- Hospitalizations for infectious illnesses were higher after COVID-19 (RR 1.41; 95% CI 1.37–1.45), including sepsis and respiratory infections.
- Compared with influenza admissions, COVID-19 admissions had higher rates of subsequent infectious hospitalizations (RR 1.24) and sepsis (RR 1.35).
- Individuals with ≥3 vaccinations did not show elevated long-term healthcare utilization compared with test-negative controls (RR 1.03; 95% CI 0.981–1.081).
Methodological Strengths
- Very large, spatiotemporally aligned cohorts with inverse probability weighting to balance covariates
- Multiple validation comparisons including influenza-admitted cohort and broad laboratory-based outcomes
Limitations
- Observational design with potential residual confounding
- VA population may limit generalizability (e.g., sex distribution, comorbidity profile)
Future Directions: Prospective immunophenotyping to define mechanisms of post-COVID immune vulnerability; trials of targeted prophylaxis or vaccination schedules in high-risk groups.
BACKGROUND: SARS-CoV-2 infection leads to post-acute sequelae that can affect nearly every organ system, including the immune system. However, whether an infection with SARS-CoV-2 is associated with increased risk of future infections with other pathogens is not yet fully characterised. In this study, we aimed to test the association between a positive test for COVID-19, compared with a negative test, and rates of future infections with other pathogens. METHODS: We used the US Department of Veterans Affairs health-care databases to build a spatiotemporally aligned cohort of 231 899 people with a positive COVID-19 test and 605 014 with a negat
2. Investigating the Long-Term Effects of COVID-19 Infection on Health Care Utilization in Individuals With COPD.
Among 31,540 matched COPD pairs, COVID-19 positivity increased long-term healthcare utilization by 9% (RR 1.09), with higher rates during wild-type/Alpha/Beta (RR 1.16) and still elevated during Omicron (RR 1.051). Those with ≥3 vaccine doses did not exhibit increased long-term utilization compared with test-negative COPD patients.
Impact: Clarifies durable healthcare burden in COPD after COVID-19 and demonstrates mitigation with ≥3 vaccinations, informing post-COVID care pathways and vaccination policy for vulnerable populations.
Clinical Implications: Plan proactive post-COVID follow-up in COPD (especially after earlier variants), emphasize booster vaccination to prevent prolonged healthcare needs, and integrate pulmonary rehab and exacerbation prevention in long-COVID clinics.
Key Findings
- COVID-19 positivity raised per-person per-year healthcare utilization by 9% vs. matched negatives (RR 1.09; 95% CI 1.067–1.127).
- Variant-era stratification: wild-type/Alpha/Beta RR 1.16 and Omicron RR 1.051 for healthcare utilization.
- Vaccination ≥3 doses eliminated excess utilization (RR 1.03; 95% CI 0.981–1.081).
Methodological Strengths
- Large matched cohort with propensity matching on key factors (age, sex, vaccination, test date)
- Variant-era and vaccination-stratified analyses with per-person-year rate modeling
Limitations
- Administrative data may miss clinical nuance and non-captured encounters
- Residual confounding and misclassification of COPD severity possible
Future Directions: Evaluate targeted interventions (e.g., boosters, pulmonary rehab, remote monitoring) to reduce post-COVID utilization in COPD; mechanistic studies on persistent symptom drivers.
BACKGROUND: Individuals with COPD are at elevated risk of severe outcomes following COVID-19 infection. RESEARCH QUESTION: Does COVID-19 have a long-term impact on health care utilization (HCU) for individuals with COPD? STUDY DESIGN AND METHODS: This retrospective matched cohort study was conducted by using health administrative data from Ontario, Canada, between April 2020 and June 2022. Individuals with physician-diagnosed COPD who underwent COVID-19 polymerase chain reaction (PCR) testing were included. Patients positive and negative for COVID-19 were matched on age, sex, vaccination status, PCR test date, and a propensity score. Patients were followed up from the end of the acute infection period (12 weeks after PCR) until the study end date. Per-person per-year HCU rates were captured and compared. Analyses were stratified according to COVID-19 variant eras (wild-type/Alpha/Beta, Delta, and Omicron) and vaccination status (0, 1, 2, and ≥ 3). RESULTS: A total of 31,540 matched pairs were identified. Mean age was 66.4 years, and 49.9% were male. Individuals with positive COVID-19 test results had 9% higher HCU rates than those who tested negative (rate ratio [RR], 1.09; 95% CI, 1.067-1.127). Stratifying according to variant, wild-type/Alpha/Beta and Omicron variants had 16% (RR, 1.16; 95% CI, 1.119-1.22) and 5% (RR, 1.051; 95% CI, 1.01-1.092) higher HCU rates, respectively. Individuals with ≥ 3 vaccinations did not have elevated rates of HCU (RR, 1.03; 95% CI, 0.981-1.081) compared with those who tested negative. INTERPRETATION: In this study, patients with COPD who were positive for COVID-19 had significantly greater long-term HCU usage. Although Omicron has been considered milder than previous variants, it was still associated with significantly elevated long-term HCU. Individuals with ≥ 3 vaccinations who tested positive for COVID-19 had HCU rates similar to those who tested negative, suggesting that vaccinations can reduce long-term HCU.
3. Sex differences in COPD in relation to smoking exposure: a population-based cohort study.
In over 105,000 adults, increasing smoking exposure conferred steeper risk increases in airway obstruction, chronic bronchitis, dyspnea, exacerbations, respiratory mortality, and all-cause mortality in women versus men. For example, exacerbation HRs rose from 4.64 (10 pack-years) to 41.6 (≥50 pack-years) in women versus 2.21 to 23.7 in men, highlighting sex-specific susceptibility.
Impact: This large, well-characterized cohort clarifies sex-based vulnerability to smoking-related COPD outcomes, informing risk stratification, screening, and cessation priorities.
Clinical Implications: Strengthen sex-tailored smoking cessation strategies, consider earlier COPD screening and exacerbation prevention in women with lower pack-year thresholds, and integrate sex-specific risk in counseling and policy.
Key Findings
- Risk increases with higher smoking were greater in women for airway obstruction, chronic bronchitis, and dyspnea.
- Exacerbation HRs vs never-smokers rose more steeply in women (10 pack-years: 4.64; ≥50 pack-years: 41.6) than in men (2.21 to 23.7).
- Respiratory mortality HRs increased to 11.1 in women vs 5.66 in men at ≥50 pack-years; all-cause mortality HRs similarly rose more in women.
Methodological Strengths
- Population-based large cohort with long follow-up (median 9.3 years)
- Sex interaction modeling with multivariable adjustment across multiple COPD-relevant outcomes
Limitations
- Observational design susceptible to residual confounding (e.g., exposure misclassification, lifestyle factors)
- Generalisability may vary outside the Danish population
Future Directions: Investigate biological and social determinants underlying sex differences; test sex-specific thresholds for screening and prevention strategies.
BACKGROUND: Sex discrepancies in the association between smoking and development and prognosis of chronic obstructive pulmonary disease (COPD) are controversial. We tested the hypothesis that females compared with males are more susceptible to the detrimental effects of smoking in relation to COPD. METHODS: We identified 47 231 males and 57 806 females from the Copenhagen General Population Study. Smoking amount was assessed with sex interaction against COPD-related outcomes, including the cross-sectional association with airway obstruction, chronic bronchitis and dyspnoea, assessed using logistic regression analyses, and longitudinal association with exacerbation and mortality, assessed using Cox proportional hazard regression adjusted for potential confounders. RESULTS: The increase in risk of airway obstruction (N=7367), chronic bronchitis (N=9206) and dyspnoea (N=8541) with higher smoking amount was greater in females compared with males. During 15 years' follow-up (median 9.3 years), the increase in risk of exacerbation (events=2756), respiratory mortality (events=711) and all-cause mortality (events=10 658) with higher smoking was greater for females compared with males. Compared with never-smokers, adjusted HRs for exacerbation increased from 4.64 (95% CI 2.83 to 7.61) in females with 10 pack-years to 41.6 (95% CI 28.8 to 60.2) in females with ≥50 pack-years, and from 2.21 (95% CI 0.92 to 5.32) in males with 10 pack-years to 23.7 (95% CI 12.9 to 43.5) in males with ≥50 pack-years. Corresponding HR increases for respiratory mortality were 2.04 (95% CI 1.27 to 3.26) to 11.1 (95% CI 7.39 to 16.8) in females and 1.09 (95% CI 0.62 to 1.92) to 5.66 (95% CI 3.96 to 8.11) in males, and for all-cause mortality, HR increases were 1.50 (95% CI 1.34 to 1.67) to 3.53 (95% CI 3.11 to 4.00) in females and 1.62 (1.45-1.81) to 2.94 (2.69-3.21) in males, respectively. CONCLUSIONS: Females seem more susceptible to the detrimental effects of smoking in development and prognosis of COPD compared with males.