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A load of hot air? – health effects of gas for cooking and heating compared to other energy sources: a systematic review and meta-analyses
Household air pollution has been estimated to be responsible for 3.2 million preventable deaths every year globally. With biomass exposure and environmental pollution linked to exacerbations of airways disease, this health impact disproportionately affects low and middle income countries. Puzzolo et al (Lancet Resp Med 2024;12(4):281–293) undertook a systematic review and included 116 studies in the subsequent meta-analyses, to compare use of gaseous fuels in the domestic environment with more polluting fuels (wood/charcoal/kerosene) and cleaner fuels (electricity/solar) with no point of use pollution. Use of gas significantly decreased the risk of COPD (OR 0·37, 95%CI 0·23–0·60; p<0·0001), pneumonia (OR 0·54, 0·38–0·77; p=0·0008), deficits in lung function (OR 0·27, 0·17–0·44; p<0·0001), severe respiratory illness or death (OR 0·27, 0·11–0·63; p=0·0024) compared with more polluting fuels. Preterm births (OR 0·66, 0·45–0·97; p=0·033), and low birth weights were similarly reduced (OR 0·70, 0·53–0·93; p=0·015). Risk of asthma did not reach statistical significance. Gas compared with electricity did increase risk of COPD (OR 1·15, 1·06–1·25; p=0·0011) and pneumonia (OR 1·26, 1·03–1·53; p=0·025) but this was not significant in all studies. While having its own health and environmental impacts, switching to gas from more polluting fuels may reduce the burden of health risk in countries without infrastructure to support reliable access to electricity. Causality is difficult to prove from the many observational studies included, but this timely review adds weight to initiatives to expand cleaner forms of domestic energy use.
Catch me if you can – early detection of CT changes and risk factors for FEV1 decline in young smokers without known lung disease
COPD is the third leading cause of death globally and with current treatments unable to reverse lung damage, early detection and risk factor management is crucial. Ritchie/Donaldson et al (Am J Respir Crit Care Med 2024;209(10):1208–1218) compared 431 smokers (median 16 pack year history) aged 30–45 with normal lung function (FEV1>80% predicted, mean 101%) to 67 non-smokers, following them up every 6 months for median 32 months. Participants underwent quantitative CT scanning, to detect and quantify (by % total lung volume) subtle parenchymal abnormalities using disease probability measures and texture analysis methods incorporating machine learning. Smokers demonstrated greater ground glass opacities (1.3% vs 0.3%, p<0.001), air trapping (7.4% vs 4.7%; p<0·001) and a calculation of airway wall thickness, termed Pi10 (3.85 mm vs 3.78 mm; p<0·001). Emphysema levels were low in both groups and there was no significant difference in the presence of emphysema between groups (0.05% vs 0.03%, p=0.146). Increased ground glass, air trapping and emphysema resulted in significantly increased FEV1 loss per year (3.4, 1.5, and 19.5 mls/year respectively per 1% increase in CT parameter), as did CT evidence of airway thickening, bronchovascular prominence and ratio of small vessel: pulmonary vessel blood volume. In addition, 24% of smokers with chronic bronchitis symptoms suffered an additional loss of 32.6mls in FEV1/year. This paper adds to our understanding of the natural history of lung disease in young smokers, highlighting the potential impact of detectable small airway changes and symptoms long before a diagnosis of COPD is made.
Fifty shades of grey – association between ground glass opacities, systemic inflammation and progression of emphysema
Interstitial lung abnormalities (ILAs) in COPD patients are associated with worse respiratory outcomes including mortality. ILAs encapsulate a number of different CT findings and the significance of individual components in terms of progression and outcome is not fully understood. Fortis et al (Am J Respir Crit Care 2024, DOI: 10.1164/rccm.202310–1825OC) reviewed the data of 2714 participants from the SPIROMICS study (1680 with COPD, 1034 with normal spirometry), to assess if ground glass opacities (GGO) were associated with increased systemic inflammation and progression of emphysema. GGO% (% volume of lung with ground glass appearances) was quantitated using complex CT methods using texture analysis and machine learning. In COPD patients, current smokers demonstrated higher GGO% than former smokers (2.93% vs 2.25%; p<0.001) and higher GGO% was associated with an increase in developing emphysema over 12 months (relative increase 11.7%, 95%CI 7.5 - 16.1; p<0.001) although FEV1 was not significantly decreased in this time (contrasting with Ritchie/Donaldson et al who followed patients for a longer period of 32 months). Higher GGO% was also associated with an increased white cell (0.3×109 /L, 0.11–0.48; p=0.001) and neutrophil count (0.25×109 /L, 0.11–0.41; p=0.001) suggesting systemic inflammation may play a role. Overall, increased GGO% was associated with more exacerbations (incidence rate ratio 1.13, 95%CI 1.003 - 1.28; p=0.045) and mortality (HR 1.54, 1.14–2.10; p=0.005) over median follow-up 1544 days. This has important implications as with increased CT screening, ILAs (including GGO) are likely to be found in increasing numbers and may indicate those at greater risk of COPD progression.
A perfect storm – inhaled treprostinil displays no benefit in COPD associated with pulmonary hypertension
Pulmonary hypertension (PH) results in an increased symptomatic burden and mortality in those with COPD (PH-COPD). Inhaled treprostinil (a prostacyclin analogue) is licensed in the US for group 1 and 3 PH, the latter in part due to results from the INCREASE trial, which demonstrated improvement in 6 min walk distance (6MWD) in ILD patients with PH. Nathan et al (Eur Respir J 2024;63(6):2400172) present results from the PERFECT study, a double blind cross-over trial of inhaled treprostinil vs placebo in PH-COPD patients. Included participants had a mean pulmonary artery pressure≥30 mmHg and pulmonary vascular resistance≥4 WU on right heart catheterisation. A contingent parallel design was in place given recruitment difficulties exacerbated by covid (total n=76 from both arms). The trial was terminated early due to an unfavourable risk benefit profile, with the primary outcome of 6MWD after 12 weeks demonstrating a worsening of 4.47 m and an early signal suggesting increased mortality in the treprostinil group (six deaths compared with 0 randomised to placebo). Serious adverse events were reported in 25.8% of the active group vs 10.3% in the placebo arm. This trial was limited by recruitment difficulties and high dropout rate but risks of treprostinil outweighed benefits in this cohort, contrasting with the results of the INCREASE study in ILD. The reasons for this are unclear, but a need for effective treatment options in PH-COPD remains and prompts further investigation.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Commissioned; internally peer reviewed.