Reduced lung function and cause-specific mortality: A population-based study of Norwegian men followed for 26 years

Prediction of maximum oxygen uptake over time in adults: analysis from the FRIEND registry

Maximum oxygen uptake (V̇O2max) equations from developed countries are inaccurate for developing countries. Accordingly, we aimed to develop equations to predict treadmill V̇O2max over time based on variables other than exercise test in adults from the USA and Brazil undergoing cardiopulmonary exercise testing (CPET). We analyzed data from 2,170 adults who underwent two CPETs (1,307 men; 20-85 years) from the USA (n=1,880) and Brazil (n=290) with a second test after 2.0±1.7 years on average. We fit linear mixed-effects models to develop equations using 90% of the sample, randomly selected. In the remaining 10% of the cohort, we used the coefficient of variation, intraclass correlation coefficient, and the Bland and Altman plots to cross-validate the optimal equation. Our best linear mixed model equation was as follows: V̇O2max (mLO2·kg-1·min-1) = 62.01 - (0.23×Ageyears) - (0.001×Age×Age) - (0.65×Body mass indexkg/m 2) + (5.47×Sexfemales=0; males=1) + (2.78×CountryBrazil=0; USA=1) - (0.68×Arterial hypertensionno=0; yes=1) - (0.45×Hyperlipidemiano=0; yes=1) - (2.02×Smokingno=0; yes=1) - (4.36×Insufficiently activeno=0; yes=1) - (1.67×Beta-blockersno=0; yes=1); R2=0.566. Our main equation was reliable at baseline according to Bland and Altman plot results (mean difference, 0.01 mLO2·kg-1·min-1: 95%CI, -13.94 to 13.98; P=0.966) and over time (0.44 mLO2·kg-1·min-1: 95%CI, -13.5 to 12.4; P=0.439). Demographic and anthropometric attributes, cardiovascular risk, and beta-blockers are valuable for predicting V̇O2max at baseline and over time. The developed equations may apply to countries with socioeconomic and demographic characteristics such as Brazil and the USA.

Risk Factors, Morbidity, and Mortality in Association With Preserved Ratio Impaired Spirometry and Restrictive Spirometric Pattern: Clinical Relevance of Preserved Ratio Impaired Spirometry and Restrictive Spirometric Pattern

BACKGROUND

Preserved ratio impaired spirometry (PRISm) and restrictive spirometric pattern (RSP) are often considered interchangeable in identifying restrictive impairment in spirometry.

RESEARCH QUESTION

Do PRISm and RSP have different individual associations with risk factors, morbidity, and mortality?

STUDY DESIGN AND METHODS

In a cross-sectional and longitudinal study, including 26,091 Norwegian general population men (30 to 46 years of age), we explored the association of PRISm and RSP with smoking habits, BMI, education, respiratory symptoms, self-reported cardiopulmonary disease, and mortality after 26 years of follow-up. PRISm was defined as FEV1/FVC ≥ lower limit of normal (LLN) and FEV1 < LLN, and RSP was defined as FEV1/FVC ≥ LLN and FVC < LLN. We compared the associations of PRISm and RSP to airflow obstruction and normal spirometry, both as mutually (PRISm alone, RSP alone) and nonmutually exclusive (PRISm, RSP) categories, adjusting for age, BMI, smoking, and education. We also conducted sensitivity analyses using Global Initiative for Chronic Obstructive Lung Disease criteria to define spirometric abnormalities.

RESULTS

The prevalence of the mutually exclusive spirometric patterns was as follows: normal 82.4%, obstruction 11.0%, PRISm alone 1.4%, RSP alone 1.7%, and PRISm + RSP 3.5%. PRISm alone patients frequently had obesity (11.2%) and had active or previous tobacco use, commonly reporting cough, phlegm, wheeze, asthma, and bronchitis. RSP alone patients had both obesity (14.6%) and underweight (2.9%), with increased breathlessness, but similar smoking habits to patients with normal spirometry. The prevalence of heart disease was 4.6% in PRISm alone, 2.7% in RSP alone, and 1.6% in obstruction. With normal spirometry as a reference, RSP alone had increased all-cause (hazard ratio [HR], 1.57; 95% CI, 1.21-2.04), cardiovascular (HR, 1.48; 95% CI, 0.88-2.48), diabetes (HR, 6.43; 95% CI, 1.88-21.97), and cancer (excluding lung) mortality (HR, 1.51; 95% CI, 0.95-2.42). PRISm alone had increased respiratory disease mortality (HR, 4.00; 95% CI, 1.22-13.16). Patients with PRISm + RSP had intermediate characteristics and the worst prognosis. Findings were overall confirmed with nonmutually exclusive categories and Global Initiative for Chronic Obstructive Lung Disease criteria.

INTERPRETATION

Our findings indicate that PRISm and RSP are spirometric patterns with distinct risk factors, morbidity, and mortality, which should be differentiated in future studies.

Descriptive Epidemiology and Prognostic Significance of Diaphragm Thickness in the General Population: The Nagahama Study

BACKGROUND

Diaphragm thickness is a potential marker of sarcopenia in addition to muscle mass and strength at extremities. We aimed to clarify the descriptive epidemiology and prognostic significance of diaphragm thickness in the general population.

METHODS

The study participants were 3324 community residents (mean age: 61.4 ± 12.8 years) who participated in a longitudinal cohort study. Clinical parameters were obtained during the follow-up survey of the study population. Diaphragm thickness was measured from B-mode ultrasound images obtained in a supine position. Clinical and physical factors independently associated with diaphragm thickness were assessed by a linear regression model and a causal mediation analysis. All-cause mortality was determined by reviewing residential registry records. Prognostic significance of diaphragm thickness for all-cause mortality was examined using a Cox proportional hazard model analysis.

RESULTS

Diaphragm thickness was greater in men than women (end-expiration, β = 0.161, p < 0.001; end-inspiration, β = 0.156, p < 0.001) and associated with waist circumference (end-expiration, β = 0.259, p < 0.001; end-inspiration, β = 0.128, p < 0.001). Handgrip strength, smoking habit, insulin resistance and exercise habit were not associated with diaphragm thickness. Skeletal muscle mass index showed apparent association with diaphragm thickness, though this association was not observed after adjusting for waist circumference. Over a mean follow-up of 1686 days (15 358 person-years), there were 56 cases of all-cause mortality. Weak handgrip strength (hazard ratio = 0.95, p = 0.044) and low forced vital capacity (hazard ratio = 0.57, p = 0.045) were associated with all-cause mortality, though none of the diaphragm thickness parameters showed a significant association (thickness at end-expiration, p = 0.722; thickness at end-inspiration, p = 0.277; thickening fraction, p = 0.219).

CONCLUSIONS

Waist circumference but not parameters of sarcopenia was independently associated with diaphragm thickness. Diaphragm thickness was not associated with all-cause mortality. Diaphragm thickness may not be a marker of systemic sarcopenia.

The influencing of obesity on lung ventilation function among middle-aged and elderly people

This study examined the effect of obesity on lung ventilation function in middle-aged and older adults using data from the China Health and Retirement Longitudinal Study. Lung function was measured using peak expiratory flow, and obesity was assessed using waist circumference and body mass index (BMI). Logistic regression and the bivariate logit model were applied to analyze the data. Among the 5631 participants, 727 were obese, 1,801 had central obesity, and 2,859 had poor pulmonary function. Individuals with obesity had a higher risk of poor pulmonary ventilation (OR = 1.869, p < 0.001) and a 12.3% decrease in the probability of good lung function (dy/dx = -0.123, p < 0.001). Moreover, individuals with a higher abdominal circumference had an increased risk of poor pulmonary ventilation (OR = 1.842, p < 0.001) and a 12.1% decrease in the probability of good lung function (dy/dx = -0.121, p < 0.001). This study indicates a negative association between obesity and lung ventilation function.

Outcome-based Definition of the Lower Limit of Normal in Spirometry: A Study of 26,000 Young Adult Men

Rationale: The definition of the lower limit of normal (LLN) of spirometric variables is not well established. Objectives: To investigate the relationship between spirometric abnormalities defined with different thresholds of the LLN and clinical outcomes and to explore the possibility of using different LLN thresholds according to the pretest probability of disease. Methods: We studied the associations between prebronchodilator spirometric abnormalities (forced expiratory volume in the first second [FEV1] < LLN, forced vital capacity [FVC] < LLN, airflow obstruction, spirometric restriction) defined with different thresholds of the LLN (10th, 5th, 2.5th, 1st percentile) and multiple outcomes (prevalence of spirometric abnormalities, respiratory symptoms, all-cause and respiratory mortality) in 26,091 30- to 46-year-old men who participated in a general population survey in Norway in 1988-1990 and were followed for 26 years. Analyses were performed with both local and Global Lung Function Initiative (GLI)-2012 reference equations, stratified by pretest risk (presence or absence of respiratory symptoms), and adjusted for age, body mass index, smoking, and education. Results: In the total population, the prevalence of airflow obstruction was 11.6% with GLI-LLN10, 11.0% with Local-LLN5, 6.1% with GLI-LLN5, 7.6% with Local-LLN2.5, and 3.5% with GLI-LLN2.5. The prevalence of spirometric restriction was 5.9% with GLI-LLN10, 5.2% with Local-LLN5, and 2.8% with GLI-LLN5. Increasingly lower thresholds of the LLN were associated with increasingly higher odds of respiratory symptoms and hazard of mortality for all spirometric abnormalities with both reference equations. Spirometric abnormalities defined with Local-LLN2.5 in asymptomatic subjects were associated with lower hazard of all-cause mortality (hazard ratio [HR], 1.50; 95% confidence interval [CI], 1.15-1.95 for FEV1 < LLN) than those defined with Local-LLN5 in the general population (HR, 1.67; 95% CI, 1.50-1.87 for FEV1 < LLN) and symptomatic subjects (HR, 1.67; 95% CI, 1.46-1.91 for FEV1 < LLN). Overall, the prevalence of spirometric abnormalities and associations with outcomes obtained with Local-LLN5 were comparable to those obtained with GLI-LLN10 and those obtained with Local-LLN2.5 to GLI-LLN5. Conclusions: There is a relationship between statistically based thresholds of the LLN of spirometric variables and clinical outcomes. Different thresholds of the LLN may be used in different risk subgroups of subjects, but the choice of the threshold needs to be evaluated together with the choice of reference equations.

The relationship between cardiometabolic index and pulmonary function among U.S. adults: insights from the National Health and Nutrition Examination Survey (2007-2012)

BACKGROUND

Previous findings have revealed that disorders of lipid metabolism may be a risk factor for pulmonary function damage; however, the combined effect of dyslipidemia and central obesity on pulmonary function is unclear. The cardiometabolic index (CMI) is a composite of serum lipids (triglyceride (TG)/high-density lipoprotein cholesterol (HDL-C)) and visceral fat parameters (waist-to-height ratio (WHtR)). This research aimed to investigate the link between CMI and pulmonary function, employing large-scale demographic data sourced from the National Health and Nutrition Examination Survey (NHANES) database.

METHODS

This cross-sectional study used data involving 4125 adults aged 20 and above collected by NHANES between 2007 and 2012. We defined CMI as the exposure variable and measured outcomes using forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC to evaluate pulmonary function. Weighted multiple linear regression models and subgroup analyses were employed to investigate separate relationships between CMI and pulmonary function. In addition, to investigate variations across different strata and evaluate the robustness of the findings, interaction tests and sensitivity analyses were conducted.

RESULTS

Results from the weighted multiple linear regression analysis indicated a unit increase in log2-CMI was associated with a reduction of 82.63 mL in FEV1 and 112.92 mL in FVC. The negative association remained significant after transforming log2-CMI by quartile (Q). When the log2-CMI level reached Q4, β coefficients (β) were -128.49 (95% CI: -205.85, -51.13), -169.01 (95% CI: -266.72, -71.30), respectively. According to the interaction test findings, the negative association linking log2-CMI with FEV1 and FVC persists regardless of confounding factors including age, gender, BMI, physical activity (PA), and smoking status. A subsequent sensitivity analysis provided additional confirmation of the stability and reliability of the results. For females, the inflection points for the nonlinear relationships between log2-CMI and FEV1, as well as log2-CMI and FVC, were identified at 2.33 and 2.11, respectively. While in males, a consistent negative association was observed.

CONCLUSIONS

Our findings suggest that higher CMI is associated with lower FEV1 and FVC. CMI may serve as a complementary consideration to the assessment and management of pulmonary function in clinical practice.

Intergenerational trauma and long-term lung dysfunction: Early life exposures and pulmonary function in Indigenous Australian adults

See related article