Associations of lifelong cigarette consumption and hypertension with airflow limitation in primary care clinic outpatients in Japan

Much lower prevalence and mortality of chronic obstructive pulmonary disease in Japan than in the US despite higher smoking rates: A meta analysis/systematic review

BACKGROUND

A recent systematic review showed Japan's mortality from chronic obstructive pulmonary disease (COPD) is the lowest among 204 countries, despite notably higher smoking rates in men in Japan than in the US. This study aims to compare (1) trends in smoking rates, (2) trends in COPD mortality, and (3) the spirometry-based COPD prevalence in the general adult population between Japan and the US.

METHODS

Age- and sex-specific smoking rates from the 1980s through 2010s and COPD mortality from 1999 through 2019 were obtained from national surveys and official statistics (International Classification of Diseases-10th codes J40-44), respectively. A systematic review and meta-analysis was performed to estimate COPD prevalence in Japan, while the National Health and Nutrition Examination Survey 2007-2012 was used for the US. A fixed ratio of 0.7 of forced expiratory volume in the first second of forced vital capacity was used to define COPD.

RESULTS

Over the past four decades, men in Japan consistently had 20-30% higher smoking rates than their US counterparts. From 1999-2019, age-adjusted COPD mortality in men in Japan was only a third of the US, whereas that in women was less than a tenth in 2019. Synthesizing data from 11 studies, involving 89,955 participants, Japan's COPD prevalence was more than 10% lower than in the US in almost all age groups for both sexes.

CONCLUSIONS

This study showed markedly lower rates of COPD in Japan than in the US. Investigating factors contributing to the paradoxical observations could lead to advancing COPD risk reduction strategies.

Undiagnosed and 'overdiagnosed' COPD using postbronchodilator spirometry in primary healthcare settings: a systematic review and meta-analysis

BACKGROUND

Despite chronic obstructive pulmonary disease (COPD) being a major global cause of mortality and hospitalisation, it is often undiagnosed or inaccurately diagnosed in clinical settings.

OBJECTIVE

To systematically synthesise all peer-reviewed papers from primary healthcare settings that have reported data on: (1) undiagnosed COPD, that is, patients with respiratory symptoms and postbronchodilator airflow obstruction consistent with COPD, without a formal clinician's diagnosis of COPD either documented in health records or reported by patients and (2) 'overdiagnosed COPD', that is, clinician's diagnosis without postbronchodilator airflow obstruction.

METHODS

Studies investigating these diagnostic metrics in patients from primary healthcare clinics (according to predefined inclusion/exclusion criteria) were sourced from Medline and Embase and assessed for bias (Johanna Briggs Institute tools for prevalence studies and case series). Meta-analyses of studies of adequate sample size used random effect modelling stratified by risk factor categories.

RESULTS

Of 26 eligible articles, 21 cross-sectional studies investigated 3959 cases of spirometry-defined COPD (with or without symptoms), and 5 peer-reviewed COPD case series investigated 7381 patients. The prevalence of spirometry-confirmed COPD without a diagnosis documented in their health records was 14%-26% in studies of symptomatic smokers (N=3). 1 in 4 patients taking inhaled therapies (25% (95% CI 22% to 28%), N=2) and 1 in 6 smokers irrespective of symptoms (16% (95% CI 14% to 18%), N=6) fulfilled diagnostic spirometry criteria but did not report receiving a COPD-related diagnosis. In an adequately powered series of COPD cases documented in primary healthcare records (N=4), only between 50% and 75% of subjects had any airflow obstruction on postbronchodilator spirometry performed by study researchers, therefore, COPD was clinically 'overdiagnosed' in 25%-50% of subjects.

DISCUSSION

Although data were heterogeneous and of modest quality, undiagnosed COPD was common in primary healthcare, especially for symptomatic smokers and patients treated with inhaled therapies. In contrast, frequent COPD 'overdiagnosis' may represent treatment of asthma/reversible component or another medical diagnosis.

PROSPERO REGISTRATION NUMBER

CRD42022295832.

A scoring system to detect fixed airflow limitation in smokers from simple easy-to-use parameters

No validated screening method currently exists for Chronic Obstructive Pulmonary Disease (COPD) in smokers. Therefore, we constructed a predictive model with simple parameters that can be applied for COPD screening to detect fixed airflow limitation. This observational cross-sectional study included a random sample of 222 smokers with no previous diagnosis of COPD undertaken in a Spanish region in 2014-2016. The main variable was fixed airflow limitation by spirometry. The secondary variables (COPD factors) were: age, gender, smoking (pack-years and Fagerström test), body mass index, educational level, respiratory symptoms and exacerbations. A points system was developed to predict fixed airflow limitation based on secondary variables. The model was validated internally through bootstrapping, determining discrimination and calibration. The system was then integrated into a mobile application for Android. Fifty-seven patients (25.7%) presented fixed airflow limitation. The points system included as predictors: age, pack-years, Fagerström test and presence of respiratory symptoms. Internal validation of the system was very satisfactory, both in discrimination and calibration. In conclusion, a points system has been constructed to predict fixed airflow limitation in smokers with no previous COPD. This system can be integrated as a screening tool, though it should be externally validated in other geographical regions.