Path analysis of familial resemblance of pulmonary function and cigarette smoking

Evidence of correlations between human partners based on systematic reviews and meta-analyses of 22 traits and UK Biobank analysis of 133 traits

Positive correlations between mates can increase trait variation and prevalence, as well as bias estimates from genetically informed study designs. While past studies of similarity between human mating partners have largely found evidence of positive correlations, to our knowledge, no formal meta-analysis has examined human partner correlations across multiple categories of traits. Thus, we conducted systematic reviews and random-effects meta-analyses of human male-female partner correlations across 22 traits commonly studied by psychologists, economists, sociologists, anthropologists, epidemiologists and geneticists. Using ScienceDirect, PubMed and Google Scholar, we incorporated 480 partner correlations from 199 peer-reviewed studies of co-parents, engaged pairs, married pairs and/or cohabitating pairs that were published on or before 16 August 2022. We also calculated 133 trait correlations using up to 79,074 male-female couples in the UK Biobank (UKB). Estimates of the 22 mean meta-analysed correlations ranged from rmeta = 0.08 (adjusted 95% CI = 0.03, 0.13) for extraversion to rmeta = 0.58 (adjusted 95% CI = 0.50, 0.64) for political values, with funnel plots showing little evidence of publication bias across traits. The 133 UKB correlations ranged from rUKB = -0.18 (adjusted 95% CI = -0.20, -0.16) for chronotype (being a 'morning' or 'evening' person) to rUKB = 0.87 (adjusted 95% CI = 0.86, 0.87) for birth year. Across analyses, political and religious attitudes, educational attainment and some substance use traits showed the highest correlations, while psychological (that is, psychiatric/personality) and anthropometric traits generally yielded lower but positive correlations. We observed high levels of between-sample heterogeneity for most meta-analysed traits, probably because of both systematic differences between samples and true differences in partner correlations across populations.

Effects of genetics and altitude on lung function

OBJECTIVES

The aim of this work is to present a review on the impact of genetics and altitude on lung function from classic and recent studies.

DATA SOURCE

A systematic search has been carried out in different databases of scientific studies, using keywords related to lung volumes, spirometry, altitude and genetics.

RESULTS

The results of this work have been structured into three parts. First, the relationship between genes and lung function. Next, a review of the genetic predispositions related to respiratory adaptation of people who inhabit high-altitude regions for millennia. Finally, temporary effects and long-term acclimatisation on respiratory physiology at high altitude are presented.

CONCLUSIONS

The works focused on the influence of genetics and altitude on lung function are currently of interest in terms of studying the interactions between genetic, epigenetic and environmental factors in the configuration of the pathophysiological adaptation patterns.

Spirometric traits show quantile-dependent heritability, which may contribute to their gene-environment interactions with smoking and pollution

BACKGROUND

"Quantile-dependent expressivity" refers to a genetic effect that is dependent upon whether the phenotype (e.g., spirometric data) is high or low relative to its population distribution. Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and the FEV1/FVC ratio are moderately heritable spirometric traits. The aim of the analyses is to test whether their heritability (h2 ) is constant over all quantiles of their distribution.

METHODS

Quantile regression was applied to the mean age, sex, height and smoking-adjusted spirometric data over multiple visits in 9,993 offspring-parent pairs and 1,930 sibships from the Framingham Heart Study to obtain robust estimates of offspring-parent (βOP), offspring-midparent (βOM), and full-sib regression slopes (βFS). Nonparametric significance levels were obtained from 1,000 bootstrap samples. βOPs were used as simple indicators of quantile-specific heritability (i.e., h 2 = 2βOP/(1+rspouse), where rspouse was the correlation between spouses).

RESULTS

βOP ± standard error (SE) decreased by 0.0009 ± 0.0003 (P = 0.003) with every one-percent increment in the population distribution of FEV1/FVC, i.e., βOP ± SE were: 0.182 ± 0.031, 0.152 ± 0.015; 0.136 ± 0.011; 0.121 ± 0.013; and 0.099 ± 0.013 at the 10th, 25th, 50th, 75th, and 90th percentiles of the FEV1/FVC distribution, respectively. These correspond to h2  ± SEs of 0.350 ± 0.060 at the 10th, 0.292 ± 0.029 at the 25th, 0.262 ± 0.020 at the 50th, 0.234 ± 0.025 at the 75th, and 0.191 ± 0.025 at the 90th percentiles of the FEV1/FVC ratio. Maximum mid-expiratory flow (MMEF) h2  ± SEs increased 0.0025 ± 0.0007 (P = 0.0004) with every one-percent increment in its distribution, i.e.: 0.467 ± 0.046, 0.467 ± 0.033, 0.554 ± 0.038, 0.615 ± 0.042, and 0.675 ± 0.060 at the 10th, 25th, 50th, 75th, and 90th percentiles of its distribution. This was due to forced expiratory flow at 75% of FVC (FEF75%), whose quantile-specific h2 increased an average of 0.0042 ± 0.0008 for every one-percent increment in its distribution. It is speculated that previously reported gene-environment interactions may be partially attributable to quantile-specific h2 , i.e., greater heritability in individuals with lower FEV1/FVC due to smoking or airborne particles exposure vs. nonsmoking, unexposed individuals.

CONCLUSION

Heritabilities of FEV1/FVC, MMEF, and FEF75% from quantile-regression of offspring-parent and sibling spirometric data suggest their quantile-dependent expressivity.

Lung function: population epidemiology and concordance in Australian children aged 11-12 years and their parents

OBJECTIVES

To describe the epidemiology of lung function in Australian children aged 11-12 years and their parents, and explore the degree of intergenerational concordance.

DESIGN

Cross-sectional study (the Child Health CheckPoint) nested in the Longitudinal Study of Australian Children (LSAC).

SETTING

Assessment centres in seven Australian cities and eight regional towns, February 2015 to March 2016. Families unable to attend a clinic appointment were offered a home visit during the same period.

PARTICIPANTS

1874 families (53% of all eligible) participated in the study. Lung function data were available for 1759 children aged 11-12 years and 1774 parents (1668 biological pairs).

OUTCOME MEASURES

Participants completed spirometry with measures including forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC) and mid expiratory flow (MEF), converted to z-scores using Global Lung Initiative equations. Parent-child concordance was assessed using Pearson's correlation coefficients and multivariable linear regression models. Survey weights and methods accounted for LSAC's complex sampling, stratification and clustering within postcodes.

RESULTS

All lung function measures followed approximately normal distributions. Mean (SD) for FEV₁, FVC and MEF z-scores in children were 0.33 (1.07), 0.83 (1.14) and -0.48 (1.09), respectively. Mean (SD) in parents were 0.28 (1.10), 0.85 (1.15) and -0.45 (1.10), respectively. Parent FEV₁, FVC and MEF were associated with child lung function with significant positive correlation coefficients (0.22, 95% CI 0.17 to 0.26; 0.24, 95% CI 0.20 to 0.29; and 0.24, 95% CI 0.20 to 0.29, respectively).

CONCLUSIONS

Mean lung volumes were larger but with smaller airway size than international standards for both parents and children in this population sample. Modest associations between parent and child lung function highlight the potential for better identification of 'at risk' populations. Therefore, these findings may aid the development of health policy that aims to prevent the onset or limit the progression of lung disease.

Genome-wide association study of lung function phenotypes in a founder population

BACKGROUND

Lung function is a long-term predictor of mortality and morbidity.

OBJECTIVE

We sought to identify single nucleotide polymorphisms (SNPs) associated with lung function.

METHODS

We performed a genome-wide association study (GWAS) of FEV1, forced vital capacity (FVC), and FEV1/FVC in 1144 Hutterites aged 6 to 89 years, who are members of a founder population of European descent. We performed least absolute shrinkage and selection operation regression to select the minimum set of SNPs that best predict FEV1/FVC in the Hutterites and used the GRAIL algorithm to mine the Gene Ontology database for evidence of functional connections between genes near the predictive SNPs.

RESULTS

Our GWAS identified significant associations between FEV1/FVC and SNPs at the THSD4-UACA-TLE3 locus on chromosome 15q23 (P = 5.7 × 10(-8) to 3.4 × 10(-9)). Nine SNPs at or near 4 additional loci had P < 10(-5) with FEV1/FVC. Only 2 SNPs were found with P < 10(-5) for FEV1 or FVC. We found nominal levels of significance with SNPs at 9 of the 27 previously reported loci associated with lung function measures. Among a predictive set of 80 SNPs, 6 loci were identified that had a significant degree of functional connectivity (GRAIL P < .05), including 3 clusters of β-defensin genes, 2 chemokine genes (CCL18 and CXCL12), and TNFRSF13B.

CONCLUSION

This study identifies genome-wide significant associations and replicates results of previous GWASs. Multimarker modeling implicated for the first time common variation in genes involved in antimicrobial immunity in airway mucosa that influences lung function.

Path analysis of factors for functional outcome at one year in 463 proximal humeral fractures

BACKGROUND

Path analysis methods were used to test the prognostic value of 10 patient-related and treatment-related factors on the 1-year functional outcome of 463 proximal humeral fractures measured using the Constant score. Complex inter-relationships between these factors were also evaluated.

MATERIALS AND METHODS

Data were collected from a prospective cohort study that included 3 operative groups repaired using nail or plate fixation and 1 nonoperative group. From the available information, various factors potentially having a direct influence on the functional Constant score were identified. The process of creating a hypothetical causal path diagram was undertaken to order the factors in a sequence of associations or cause-and-effect relationships.

RESULTS

Our final multivariable regression model for the 1-year Constant score included the 6 factors of age, sex, treatment, occurrence of intraoperative and local post-treatment complications, and anatomic restoration. Being a woman aged older than 40 years, treated with a locking proximal humeral plate (LPHP), having experienced intraoperative and local post-treatment complications, and varus deformity of more than 30° were negative predictors of the Constant score (ie, poor shoulder function 1 year after treatment initiation). Three factors, the dominant side fractured and the Neer and AO fracture type, showed only significant association on intermediate factors. The presence of concomitant disease did not show any significant direct or indirect effect. A final pathway outlines these associations and inter-relationships.

CONCLUSION

Prevention of local complications, in particular those leading to severe varus deviation, appears essential to improve shoulder function after a proximal humeral fracture.

Family history is a risk factor for COPD

BACKGROUND

Studies have shown that family history is a risk factor for COPD, but have not accounted for family history of smoking. Therefore, we sought to identify the effects of family history of smoking and family history of COPD on COPD susceptibility.

METHODS

We compared 821 patients with COPD to 776 control smokers from the Genetic Epidemiology of COPD (COPDGene) Study. Questionnaires captured parental histories of smoking and COPD, as well as childhood environmental tobacco smoke (ETS) exposure. Socioeconomic status was defined by educational achievement.

RESULTS

Parental history of smoking (85.5% case patients, 82.9% control subjects) was more common than parental history of COPD (43.0% case patients, 30.8% control subjects). In a logistic regression model, parental history of COPD (OR, 1.73; P < .0001) and educational level (OR, 0.48 for some college vs no college; P < .0001) were significant predictors of COPD, but parental history of smoking and childhood ETS exposure were not significant. The population-attributable risk from COPD family history was 18.6%. Patients with COPD with a parental history had more severe disease, with lower lung function, worse quality of life, and more frequent exacerbations. There were nonsignificant trends for more severe emphysema and airway disease on quantitative chest CT scans.

CONCLUSIONS

Family history of COPD is a strong risk factor for COPD, independent of family history of smoking, personal lifetime smoking, or childhood ETS exposure. Although further studies are required to identify genetic variants that influence COPD susceptibility, clinicians should question all smokers, especially those with known or suspected COPD, regarding COPD family history.

Path analysis of factors for delayed healing and nonunion in 416 operatively treated tibial shaft fractures

A prospective observational study was done in 41 trauma centers. Four hundred sixteen patients with tibial shaft fractures were treated operatively and followed up for at least 6 months. Fifty-two (13%) cases of delayed healing or nonunion were reported. In such nonrandomized observational studies, multiple interrelationships exist between prognostic factors and patient outcomes. We used path analyses to investigate prognostic factors associated with the occurrence of delayed healing or nonunion. The most important factors were identified using multivariate regression analyses, and interrelationships between factors were illustrated using a path diagram. Fractures with open injuries less than and greater than 5 cm were 3.6 and 5.7 times as likely, respectively, to have delayed healing or nonunion as fractures with no skin injuries. The Müller-AO classification of fractures did not provide additional prognostic information. The risk of healing problems was doubled for fractures of the distal shaft and for fractures showing a postoperative diastasis. Treatment options showed an indirect effect on outcome with the occurrence of diastasis. A model for predicting delayed healing or nonunion is proposed. We encourage the use of path analysis in orthopaedics as a powerful visual technique to interpret data from observational studies.

LEVEL OF EVIDENCE

Prognostic study, Level II-1 (retrospective study). See the Guidelines for Authors for a complete description of levels of evidence.

Further evidence for the role of genes on chromosome 2 and chromosome 5 in the inheritance of pulmonary function

The spirometric measurements FEV1, FVC, and the ratio FEV1/FVC are used in the diagnosis of lung function disorders. Therefore, understanding the genetics underlying these spirometric measurements will increase our knowledge of the genetics of pulmonary function. FEV1 and FVC were measured on 264 members of 26 Utah Genetic Reference pedigrees, originally collected for the Centre d'Etude du Polymorphisme Humain genetic mapping project. Using segregation analysis, we inferred major locus inheritance of the FEV1/FVC ratio, although we could not distinguish between a dominant or recessive mode of inheritance. No evidence of major locus inheritance was found for either FEV1 or FVC. Suggestive evidence of linkage for the ratio FEV1/FVC was found on chromosome 2 (heterogeneity lod = 2.36, dominant model) and chromosome 5 (heterogeneity lod = 2.23, recessive model), replicating linkages from other studies. In addition, nonparametric variance component linkage analysis showed linkage of FEV1/FVC in both of these regions, providing further support to the results. No nonparametric lod scores over 1.5 were obtained for either FEV1 or FVC.

Familial aggregation and heritability of adult lung function: results from the Busselton Health Study

Decreased spirometric indices are characteristic of asthma and other respiratory diseases. The aim of this study was to investigate the genetic and environmental components of variance of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) measured in adulthood in an Australian population-based sample of 468 Caucasian nuclear families. The inter-relationships of the genetic determinants of these traits with asthma and atopic rhinitis were also investigated. Serial cross-sectional studies were conducted in the town of Busselton in Western Australia between 1966 and 1981 and follow-up of previous attendees was undertaken in 1995. Data from each subject included in this study were from a single survey in adulthood (25-60 yrs of age) when the subject was as close to age 45 yrs as possible. Multivariate analysis suggested that FEV1 and FVC levels were associated with age, sex, height, tobacco smoke exposure, asthma and atopic rhinitis. After adjustment for relevant covariates, FEV1 levels had a narrow-sense heritability (h2N) of 38.9% (SE 9.1%). FVC levels had an h2N of 40.6% (SE 8.9%). Extended modelling demonstrated little overlap in the genetic determinants of asthma or atopic rhinitis and either FEV1 or FVC levels. The results of this study were consistent with the existence of important genetic determinants of adult lung function that are independent of asthma or other atopic disease, cigarette smoking, height, age or sex.

Major genetic effects on airway-parenchymal dysanapsis of the lung: the Humboldt family study

We examined familial resemblance and performed segregation analysis for the maximal expiratory flow rate at 50% of vital capacity (Vmax50) and the ratio of Vmax50 to forced vital capacity (FVC), based on data from 309 nuclear families with 1,045 individuals in the town of Humboldt, Saskatchewan, in 1993. Vmax50 is considered as an index of airway function and Vmax50/FVC is considered as an index of airway-parenchymal dysanapsis. Both Vmax50 and Vmax50/FVC were preadjusted for host characteristics (age, height, and weight), environmental factors, and history of respiratory symptoms and diseases in four separate groups (mothers, fathers, daughters, and sons). Both Vmax50 and Vmax50/FVC showed low father-mother correlations and significant parent-offspring and sibling-sibling correlations. Segregation analysis indicated that for residual Vmax50, the model of no-parent-offspring transmission with possible heterogeneity between two generations fitted the data as well as did the general model with arbitrary transmission probabilities. The Mendelian hypothesis for Vmax50 was rejected, which was consistent with our previous findings for other indexes of airway function. For residual Vmax50/FVC, however, a single locus explained all the familial resemblance and both no-parent-offspring-transmission hypotheses [tau(AA) = tau(AB) = tau(BB) = qA and tau(AA) = tau(AB) = tau(BB)] were rejected. The study provides evidence for a single locus influencing airway-parenchymal dysanapsis.

Segregation analysis of two lung function indices in a random sample of young families: the Humboldt Family Study

The Humboldt Family Study was conducted in the town of Humboldt, Saskatchewan, in 1993. Familial correlations and segregation analyses of lung function were carried out in 799 individuals in 214 nuclear families that included 214 fathers, 214 mothers, and 371 children. Forced expiratory volume in 1 second (FEV1) and maximal mid-expiratory flow rate (MMFR) were first regressed on age, height, weight, and their quadratic and cubic terms as well as on smoking status in four groups separately (mothers, fathers, daughters, and sons), with terms significant at the 0.10 level being retained. Residual phenotypes were standardized within the four groups. Class D regressive models were used to perform familial correlations and segregation analyses. For both FEV1 and MMFR, father-mother correlations were not significantly different from zero, and mother-offspring, father-offspring, and sibling-sibling correlations showed no statistically significant difference from each other. Based on the "polygenic" models, the estimated intraclass correlation is 0.132 (+/- 0.035) for FEV1 and 0.171 (+/- 0.039) for MMFR, and the narrow-sense heritability is 0.264 for FEV1 and 0.342 for MMFR. Segregation analysis shows that the "mixed" model with both single locus and polygenic components had a better fit for FEV1 than single-locus or polygenic only models. However, the model which included a nontransmitted environmental factor [tau(AA) = tau(AB) = tau(BB) = qA] and polygenic loci had a better fit than the Mendelian model [tau(AA) = 1, tau(AB) = 1/2, tau(BB) = 0] [Akaike's information criterion (AIC) = 2219.47 vs. AIC = 2222.14]. For MMFR, the Mendelian "mixed" model gave a nonsignificant improvement in loge likelihood compared to the simple polygenic model. Comparison of the single-locus model and Mendelian "mixed" model shows no difference in fitting the data. This study suggests that FEV1 and MMFR are controlled by many loci with no major effects and/or common environmental factors.

A path analysis of some determinants of infant growth in Khartoum

The interrelationships between some socioeconomic and behavioural characteristics of mothers and the growth and illness experience of their infants in poor Khartoum townships have been examined by path analysis. For both infant body weight and supine length it is shown that weaning age and illness experience are important determinants of growth. It is also shown that greater maternal income has disadvantageous effects through encouraging early weaning. Most importantly the infants of housewives have later weaning, less illness and greater weight and length at 1 year of age than the infants of mothers with jobs, showing the value of time for caring in the prevailing environmental circumstances.

Estimating familial aggregation while adjusting for covariates. Application to pulmonary function data from black and white sibships

Although crude correlations are useful in family studies, some adjustment for effects of risk factors that vary both within and among families if often needed. A linear model for estimating sibship correlations while simultaneously considering height, age, race, sex, ascertainment, and smoking status was used on pulmonary function data on 1-second forced expiratory volume (FEV1) and the natural logarithm of the ratio of FEV1 to forced vital capacity (lnFEV%) from 402 adults in 152 white sibships and 172 adults in 59 black sibships. Crude correlations of .271 +/- .048 (FEV1) and .342 +/- .047 (lnFEV%) decreased significantly to .206 +/- .048 and .231 +/- .048, respectively, after adjustment. For black and white sibs, adjusted intraclass correlations, although not statistically different, were .153 +/- .089 and .225 +/- .055 (FEV1), respectively, and were .103 +/- .088 and .275 +/- .054 (lnFEV%), respectively, suggesting that pulmonary function may aggregate more strongly among whites. This analysis illustrates how risk factor adjustment can be readily incorporated into familial correlation studies.