Adults with higher Life’s Crucial 9 scores had lower prevalence of respiratory symptoms and chronic lung disease as well as better lung function measures in a cross-sectional analysis of National Health and Nutrition Examination Survey data.
Researchers analyzed National Health and Nutrition Examination Survey (NHANES) data collected from 2005 to 2012 involving 10,461 US adults aged 40 years and older with complete Life’s Crucial 9 (LC9) and lung health data, according to the study abstract and weighted group totals, although the paper’s Results section separately cites 10,601 participants. LC9 expands the American Heart Association’s Life’s Essential 8 cardiovascular health framework by incorporating a mental health component. Missing covariate data were handled using Random Forest imputation methods.
The LC9 score incorporates nine domains: diet, physical activity, nicotine exposure, sleep, body mass index, blood pressure, blood glucose, blood lipids, and mental health. Patients were categorized as having low, moderate, or high cardiovascular health based on overall LC9 scores.
Among the study population, 13% of patients had low cardiovascular health, 70% had moderate cardiovascular health, and 16% had high cardiovascular health. Patients with higher LC9 scores tended to be younger, female, more highly educated, and less likely to have cardiovascular disease or secondhand smoke exposure.
Patients with higher scores also had lower rates of cough, phlegm, wheeze, asthma, emphysema, chronic bronchitis, and chronic obstructive pulmonary disease (COPD).
Respiratory symptoms and diagnoses of asthma, chronic bronchitis, and emphysema were based on self-report. Subjects with an initial forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) below 0.7 underwent repeat spirometry following bronchodilator administration, and COPD was confirmed if the ratio remained below 0.7.
In fully adjusted analyses, every 10-point increase in LC9 score was associated with lower odds of cough, phlegm, wheeze, asthma, emphysema, chronic bronchitis, and COPD. Higher LC9 scores were also associated with higher FEV1 and forced vital capacity (FVC).
The spirometry analyses were limited to NHANES 2007 to 2012 cycles because lung function data were unavailable in 2005 to 2006, meaning the FEV1 and FVC findings were based on a smaller subset of the overall cohort.
Notably, LC9 scores were not significantly associated with FEV1/FVC following full adjustment, although the study found that health behavior and health factor subscores showed opposing directional associations with that measure.
Respiratory disease prevalence differed substantially across cardiovascular health categories. Emphysema prevalence was 7% among patients with low cardiovascular health compared with less than 1% among those with high cardiovascular health. COPD prevalence was approximately 9% vs 3%, respectively.
Restricted cubic spline analyses suggested nonlinear relationships between LC9 and several respiratory outcomes. Associations with cough and asthma appeared strongest at lower LC9 scores and plateaued at higher levels. For COPD, the relationship followed an inverted U-shaped pattern, suggesting that only sufficiently high LC9 levels were associated with lower COPD burden.
Subgroup analyses showed generally consistent associations across demographic and clinical groups, although some interactions varied by age, sex, race, marital status, and cardiovascular disease status. Associations between LC9 and lung function measures appeared stronger among older patients, men, White patients, and partnered patients.
Researchers also developed machine learning prediction models using Light Gradient Boosting Machine algorithms. Predictive performance was strongest for emphysema, with an area under the curve of 0.889 in the top-feature model.
Shapley additive explanation analyses identified depression, nicotine exposure, and body mass index as the LC9 components contributing most strongly to prediction performance. High body mass index scores contributed positively to COPD prediction, which the investigators noted may relate to the previously described “obesity paradox” observed in some patients with COPD.
The findings should be interpreted cautiously because the cross-sectional design precluded conclusions about causality or whether improving LC9 scores would improve lung outcomes. Several respiratory outcomes relied partly on self-report, which may have introduced recall bias, exclusion of patients with missing data may have introduced selection bias, and residual confounding from unmeasured variables cannot be excluded.
“There is a positive correlation between LC9 score and lung health,” wrote Haolin Shi, of Beijing Friendship Hospital, Beijing Daxing District People’s Hospital, Capital Medical University Daxing Teaching Hospital, in China, and colleagues. The researchers suggested clinicians consider LC9 as a practical framework for lifestyle management in patients with cardiovascular and respiratory risk factors.
Disclosures: The researchers reported no funding and declared no competing interests.
Source: BMC Pulmonary Medicine
