Examining the relationship between the environmental impact of diet and child growth from a co-benefit perspective.

The adoption of diets that minimize both their environmental impacts and weight excess in children would be a major co-benefit for climate change mitigation. We evaluated the relationship between child diet-related environmental impact and anthropometric characteristics in an Italian birth cohort. The study involved 2127 children of the Piccolipiù birth cohort. At 4 years, their diet in the previous two months was assessed through a questionnaire, from which we derived individual: (i) diet-related daily greenhouse gas emissions (GHGE), (ii) land use (LU), (iii) adherence to the Mediterranean Diet (MD) and (iv) red meat consumption. We related these variables with overweight and obesity, waist circumference, and height at 4 years using regression models adjusted for a priori selected confounders. Diet-related GHGE and LU had a positive weak association with overweight and obesity, with an odds ratio (OR) for the fourth vs. second quartile of 1.30 for both GHGE (95% confidence intervals -CI-: 0.96; 1.77) and LU (95% CI: 0.96-1.76). Both OR estimates increased after adjustment for energy intake. GHGE and LU were not associated with height, with the exception of shorter children in the first quartile. A high vs. low MD adherence was associated with an increase in height Z-score of 0.11 (95% CI 0.01; 0.21). No association was found for red meat consumption. These results suggest that lowering the impact of high environmental impact diets may have, if anything, beneficial effects on child obesity, overweight, and height, with pro-MD patterns playing an important role.

Breastfeeding and presence of the companion of woman's choice during COVID-19 pandemic in Italy: regional population-based routine data and best practices at birth

OBJECTIVES: to describe the monthly trend of breastfeeding during hospitalization and the presence of companion of woman's choice during labour and birth, and the key regional responders' perspective of homogeneity/heterogeneity of the presence of the support person, before, during (February-May 2020), and after the first COVID-19 pandemic wave in a few Italian Regions. DESIGN: two-phase study. SETTING AND PARTICIPANTS: data from the italian birth certificate of six Italian Regions between 01.01.2019 and 31.03.2021 were analysed. Semi-structured interviews were conducted with the key regional respondents. MAIN OUTCOME MEASURES: the frequency distributions of breastfeeding and the presence of companion of woman's choice were calculated as a whole and for each Region. RESULTS: the infant feeding practices experienced smaller changes during COVID-19 pandemic than the presence of the companion of woman's choice during labour and birth, from January 2019 to March 2021. The highest value of exclusive breastfeeding was recorded in September 2020 (72.1%; 95%CI 71.3-72.8) in all Regions, while the lowest was recorded in March 2021 (62.5%; 95%CI 61.5-63.4). The presence of companion of woman's choice during labour and birth decreased during the pandemic and did not return to pre-pandemic levels. The highest value of presence of father during birth was recorded in March 2019 (59.0%; 95%CI 58.2-59.8), while the lowest in April 2020 (50.0%; 95%CI 49.1-50.8). The main emerging themes were: the existence of national, regional and local indications; the facilitators (e.g., Baby-Friendly Hospital Initiative implementation, strong motivation of the staff) and the critical points (e.g., inadequate analysis of the clinical-epidemiological context, inhomogeneous indications) of management of the support person presence. CONCLUSIONS: the emergency has changed the provision of health services that not always guaranteed the application of best practices. It would be desirable to work for assessing the appropriateness of the birth certificate data to collect more accurate information and to provide clinical recommendations.

Cord blood metabolites and rapid postnatal growth as multiple mediators in the prenatal propensity to childhood overweight.

BACKGROUND: The mechanisms underlying childhood overweight and obesity are poorly known. Here, we investigated the direct and indirect effects of different prenatal exposures on offspring rapid postnatal growth and overweight in childhood, mediated through cord blood metabolites. Additionally, rapid postnatal growth was considered a potential mediator on childhood overweight, alone and sequentially to each metabolite. METHODS: Within four European birth-cohorts (N = 375 mother-child dyads), information on seven prenatal exposures (maternal education, pre-pregnancy BMI, weight gain and tobacco smoke during pregnancy, age at delivery, parity, and child gestational age), selected as obesogenic according to a-priori knowledge, was collected. Cord blood levels of 31 metabolites, associated with rapid postnatal growth and/or childhood overweight in a previous study, were measured via liquid-chromatography-quadrupole-time-of-flight-mass-spectrometry. Rapid growth at 12 months and childhood overweight (including obesity) between four and eight years were defined with reference to WHO growth charts. Single mediation analysis was performed using the imputation approach and multiple mediation analysis using the extended-imputation approach. RESULTS: Single mediation suggested that the effect of maternal education, pregnancy weight gain, parity, and gestational age on rapid postnatal growth but not on childhood overweight was partly mediated by seven metabolites, including cholestenone, decenoylcarnitine(C10:1), phosphatidylcholine(C34:3), progesterone and three unidentified metabolites; and the effect of gestational age on childhood overweight was mainly mediated by rapid postnatal growth. Multiple mediation suggested that the effect of gestational age on childhood overweight was mainly mediated by rapid postnatal growth and that the mediating role of the metabolites was marginal. CONCLUSION: Our findings provide evidence of the involvement of in utero metabolism in the propensity to rapid postnatal growth and of rapid postnatal growth in the propensity to childhood overweight. We did not find evidence supporting a mediating role of the studied metabolites alone between the studied prenatal exposures and the propensity to childhood overweight.

Who is likely to vacillate in their COVID-19 vaccination decision? Free-riding intention and post-positive reluctance.

Despite the actual availability of COVID-19 vaccines to combat the pandemic, many people are still vacillating in their decision to vaccinate. In this study, we considered the effect of two relevant contextual issues on vaccination intention: the number of people infected with COVID-19 is increasing, and the pace of vaccination is gaining speed. Specifically, we hypothesized that having already contracted SARS-CoV-2 (post-positive reluctance) could lead people to underestimate the importance of vaccination. Moreover, as the number of vaccinated people increases, more hesitant people could fall into the free-riding intention category, benefitting from the immunity provided by others' vaccinations. Vaccine hesitancy becomes more critical as the vaccination campaign proceeds: at one point, it will be inevitable to deal with hesitant people. This study is part of a WHO Regional Office for Europe project and involved a representative sample of 5006 Italians interviewed in January-February 2021. In case of post-positive reluctance, both young age and female gender increase vaccine hesitancy, while a high level of education reduces free-riding intention. Considering post-positive reluctance and free riding, a protective effect on hesitancy is associated with negative affective states, adherence to protective behaviors, trust in health information sources, and resilience. In contrast, increased vaccine hesitancy is associated with a high level of conspiracy-mindedness and trust in media information sources. Recognizing and studying the post-positive reluctance and the phenomenon of free-riding people can help us to become more efficient in combatting the virus.

Pregnancy outcomes in Italy during COVID-19 pandemic: a population-based cohort study.

OBJECTIVE: To compare the estimates of preterm birth (PTB; 22-36 weeks gestational age, GA) and stillbirth rates during COVID-19 pandemic in Italy with those recorded in the three previous years. DESIGN: A population-based cohort study of liveborn and stillborn infants was conducted using data from Regional Health Systems and comparing the pandemic period (March 1st , 2020-March 31st , 2021, N= 362,129) to an historical period (January 2017- February 2020, N=1,117,172). The cohort covered 84.3% of the births in Italy. METHODS: Poisson regressions were run in each Region and meta-analyses were performed centrally. We used an interrupted time series regression analysis to study the trend of preterm births from 2017 to 2021. MAIN OUTCOME MEASURES: The primary outcomes were PTB and stillbirths. Secondary outcomes were late PTB (32-36 weeks' GA), very PTB (<32 weeks' GA), and extremely PTB (<28 weeks' GA), overall and stratified into singleton and multiples. RESULTS: The pandemic period compared with the historical one was associated with a reduced risk for PTB (Risk Ratio: 0.91; 95% Confidence Interval, CI: 0.88, 0.93), late PTB (0.91; 0.88, 0.94), very PTB (0.88; 0.84, 0.91), and extremely PTB (0.88; 0.82, 0.95). In multiples, point estimates were not very different, but had wider CIs. No association was found for stillbirths (1.01; 0.90, 1.13). A linear decreasing trend in PTB rate was present in the historical period, with a further reduction after the lockdown. CONCLUSIONS: We demonstrated a decrease in PTB rate after the introduction of COVID-19 restriction measures, without an increase in stillbirths.

Prenatal exposure to PM10 and changes in DNA methylation and telomere length in cord blood.

BACKGROUND: Air pollution exposure in pregnancy can cause molecular level alterations that might influence later disease susceptibility. OBJECTIVES: We investigated DNA methylation (DNAm) and telomere length (TL) in the cord blood in relation to gestational PM10 exposure and explored potential gestational windows of susceptibility. METHODS: Cord blood epigenome-wide DNAm (N = 384) and TL (N = 500) were measured in children of the Italian birth cohort Piccolipiù, using the Infinium Methylation EPIC BeadChip and qPCR, respectively. PM10 daily exposure levels, based on maternal residential address, were estimated for different gestational periods using models based on satellite data. Epigenome-wide analysis to identify differentially methylated probes (DMPs) and regions (DMRs) was conducted, followed by a pathway analysis and replication analysis in an second Piccolipiù dataset. Distributed lag models (DLMs) using weekly exposures were used to study the association of PM10 exposure across pregnancy with telomere length, as well as with the DMPs that showed robust associations. RESULTS: Gestational PM10 exposure was associated with the DNA methylation of more than 250 unique DMPs, most of them identified in early gestation, and 1 DMR. Out of 151 DMPs available in the replication dataset, ten DMPs showed robust associations: eight were associated with exposure during early gestation and 2 with exposure during the whole pregnancy. These exposure windows were supported by the DLM analysis. The PM10 exposure between 15th and 20th gestational week seem to be associated with shorter telomeres at birth, while exposure between 24th and 29th was associated with longer telomeres. DISCUSSION: The early pregnancy period is a potential critical window during which PM10 exposure can influence cord blood DNA methylation. The results from the TL analysis were consistent with previous findings and merit further exploration in future studies. The study underlines the importance of considering gestational windows outside of the predefined trimesters that may not always overlap with biologically relevant windows of exposure.

Cord blood metabolic signatures predictive of childhood overweight and rapid growth.

INTRODUCTION: Metabolomics may identify biological pathways predisposing children to the risk of overweight and obesity. In this study, we have investigated the cord blood metabolic signatures of rapid growth in infancy and overweight in early childhood in four European birth cohorts. METHODS: Untargeted liquid chromatography-mass spectrometry metabolomic profiles were measured in cord blood from 399 newborns from four European cohorts (ENVIRONAGE, Rhea, INMA and Piccolipiu). Rapid growth in the first year of life and overweight in childhood was defined with reference to WHO growth charts. Metabolome-wide association scans for rapid growth and overweight on over 4500 metabolic features were performed using multiple adjusted logistic mixed-effect models and controlling the false discovery rate (FDR) at 5%. In addition, we performed a look-up analysis of 43 pre-annotated metabolites, previously associated with birthweight or rapid growth. RESULTS: In the Metabolome-Wide Association Study analysis, we identified three and eight metabolites associated with rapid growth and overweight, respectively, after FDR correction. Higher levels of cholestenone, a cholesterol derivative produced by microbial catabolism, were predictive of rapid growth (p = 1.6 × 10-3). Lower levels of the branched-chain amino acid (BCAA) valine (p = 8.6 × 10-6) were predictive of overweight in childhood. The area under the receiver operator curve for multivariate prediction models including these metabolites and traditional risk factors was 0.77 for rapid growth and 0.82 for overweight, compared with 0.69 and 0.69, respectively, for models using traditional risk factors alone. Among the 43 pre-annotated metabolites, seven and five metabolites were nominally associated (P < 0.05) with rapid growth and overweight, respectively. The BCAA leucine, remained associated (1.6 × 10-3) with overweight after FDR correction. CONCLUSION: The metabolites identified here may assist in the identification of children at risk of developing obesity and improve understanding of mechanisms involved in postnatal growth. Cholestenone and BCAAs are suggestive of a role of the gut microbiome and nutrient signalling respectively in child growth trajectories.

Changes in parental smoking during pregnancy and risks of adverse birth outcomes and childhood overweight in Europe and North America: An individual participant data meta-analysis of 229,000 singleton births.

BACKGROUND: Fetal smoke exposure is a common and key avoidable risk factor for birth complications and seems to influence later risk of overweight. It is unclear whether this increased risk is also present if mothers smoke during the first trimester only or reduce the number of cigarettes during pregnancy, or when only fathers smoke. We aimed to assess the associations of parental smoking during pregnancy, specifically of quitting or reducing smoking and maternal and paternal smoking combined, with preterm birth, small size for gestational age, and childhood overweight. METHODS AND FINDINGS: We performed an individual participant data meta-analysis among 229,158 families from 28 pregnancy/birth cohorts from Europe and North America. All 28 cohorts had information on maternal smoking, and 16 also had information on paternal smoking. In total, 22 cohorts were population-based, with birth years ranging from 1991 to 2015. The mothers' median age was 30.0 years, and most mothers were medium or highly educated. We used multilevel binary logistic regression models adjusted for maternal and paternal sociodemographic and lifestyle-related characteristics. Compared with nonsmoking mothers, maternal first trimester smoking only was not associated with adverse birth outcomes but was associated with a higher risk of childhood overweight (odds ratio [OR] 1.17 [95% CI 1.02-1.35], P value = 0.030). Children from mothers who continued smoking during pregnancy had higher risks of preterm birth (OR 1.08 [95% CI 1.02-1.15], P value = 0.012), small size for gestational age (OR 2.15 [95% CI 2.07-2.23], P value < 0.001), and childhood overweight (OR 1.42 [95% CI 1.35-1.48], P value < 0.001). Mothers who reduced the number of cigarettes between the first and third trimester, without quitting, still had a higher risk of small size for gestational age. However, the corresponding risk estimates were smaller than for women who continued the same amount of cigarettes throughout pregnancy (OR 1.89 [95% CI 1.52-2.34] instead of OR 2.20 [95% CI 2.02-2.42] when reducing from 5-9 to ≤4 cigarettes/day; OR 2.79 [95% CI 2.39-3.25] and OR 1.93 [95% CI 1.46-2.57] instead of OR 2.95 [95% CI 2.75-3.15] when reducing from ≥10 to 5-9 and ≤4 cigarettes/day, respectively [P values < 0.001]). Reducing the number of cigarettes during pregnancy did not affect the risks of preterm birth and childhood overweight. Among nonsmoking mothers, paternal smoking was associated with childhood overweight (OR 1.21 [95% CI 1.16-1.27], P value < 0.001) but not with adverse birth outcomes. Limitations of this study include the self-report of parental smoking information and the possibility of residual confounding. As this study only included participants from Europe and North America, results need to be carefully interpreted regarding other populations. CONCLUSIONS: We observed that as compared to nonsmoking during pregnancy, quitting smoking in the first trimester is associated with the same risk of preterm birth and small size for gestational age, but with a higher risk of childhood overweight. Reducing the number of cigarettes, without quitting, has limited beneficial effects. Paternal smoking seems to be associated, independently of maternal smoking, with the risk of childhood overweight. Population strategies should focus on parental smoking prevention before or at the start, rather than during, pregnancy.

Influence of residential land cover on childhood allergic and respiratory symptoms and diseases: Evidence from 9 European cohorts.

INTRODUCTION: Recent research focused on the interaction between land cover and the development of allergic and respiratory disease has provided conflicting results and the underlying mechanisms are not fully understood. In particular, green space, which confers an overall positive impact on general health, may be significantly contributing to adverse respiratory health outcomes. This study evaluates associations between surrounding residential land cover (green, grey, agricultural and blue space), including type of forest cover (deciduous, coniferous and mixed), and childhood allergic and respiratory diseases. METHODS: Data from 8063 children, aged 3-14 years, were obtained from nine European population-based studies participating in the HEALS project. Land-cover exposures within a 500 m buffer centred on each child's residential address were computed using data from the Coordination of Information on the Environment (CORINE) program. The associations of allergic and respiratory symptoms (wheeze, asthma, allergic rhinitis and eczema) with land coverage were estimated for each study using logistic regression models, adjusted for sex, age, body mass index, maternal education, parental smoking, and parental history of allergy. Finally, the pooled effects across studies were estimated using meta-analyses. RESULTS: In the pooled analyses, a 10% increase in green space coverage was significantly associated with a 5.9%-13.0% increase in the odds of wheezing, asthma, and allergic rhinitis, but not eczema. A trend of an inverse relationship between agricultural space and respiratory symptoms was observed, but did not reach statistical significance. In secondary analyses, children living in areas with surrounding coniferous forests had significantly greater odds of reporting wheezing, asthma and allergic rhinitis. CONCLUSION: Our results provide further evidence that exposure to green space is associated with increased respiratory disease in children. Additionally, our findings suggest that coniferous forests might be associated with wheezing, asthma and allergic rhinitis. Additional studies evaluating both the type of green space and its use in relation to respiratory conditions should be conducted in order to clarify the underlying mechanisms behind associated adverse impacts.

A screening and treatment programme to deal with perinatal anxiety and depression during the COVID-19 pandemic.

During a pandemic, pregnancy and the postnatal period are complicated by multiple factors. On the one hand, worries about one's own health and the health of loved ones, in particular of the newborn child, can increase the risk of some mental disorders, such as depression and anxiety in the pregnant woman. On the other hand, as happened for the COVID-19 epidemic in Italy, given the need for physical distancing, the maintenance of the social and family network, so important for new parents in the perinatal period, is lacking. In addition, health services are forced to reorganize their offerings to ensure maximum safety for their operators and patients. This work proposes a model of screening and treatment aimed at identifying women at risk and providing them with effective and safe treatment.

Perinatal maternal mental health is associated with both infections and wheezing in early childhood.

BACKGROUND: Wheezing and infections are common during infancy, and the role of early-life exposures in their development is still under investigation. We examined associations between maternal mental health in pregnancy and after delivery and subsequent offspring wheezing and infections. METHODS: We studied 2314 mother-child pairs recruited in the Piccolipiù birth cohort (Italy) from 2011 to 2015. Maternal mental health was assessed in pregnancy and 12 months after delivery via the General Health Questionnaire-12 (GHQ-12). GHQ-12 Likert scores were collapsed into low (below the upper tercile) and high (above). Risk ratios (RR) and 95% confidence intervals (CI) between each combination of scores-during pregnancy and 1 year after delivery-and outcomes were computed by log-binomial regression models. RESULTS: High scores both in pregnancy and after delivery, compared with low scores in both periods, were associated with wheezing (RR: 1.35; 95% CI: 1.08, 1.69), recurrent (≥2 episodes) wheezing (1.35; 0.99, 1.83), any and recurrent (≥4 episodes) upper respiratory infections (1.20; 1.04, 1.41, and 1.45; 1.07, 1.97, respectively), lower respiratory infections (1.31; 1.08, 1.61), and diarrhea (1.49; 1.23, 1.80). High scores either during pregnancy or 1 year after delivery only were less consistently associated with outcomes. CONCLUSIONS: Maternal mental health problems extending from pregnancy to the first year after delivery are associated with development of both wheezing and infections. As wheezing is mostly triggered by infections, increased infection susceptibility could represent a possible common biologic mechanism. This study confirms the importance of early-life exposures on childhood health.

Lifelong exposure to multiple stressors through different environmental pathways for European populations.

Traditional exposure studies provide valuable insights for epidemiology, toxicology, and risk assessment. Throughout their lives, individuals are exposed to thousands of stressors in the environment which are not static, but influenced by environmental, temporal, spatial, and even socio-demographic factors. Existing exposure studies have usually focused on specific stressors for a constrained period of time. In response, the concept of the exposome has been raised, which is defined as the totality of exposure experienced from conception until death. The EU FP7-ENVIRONMENT research project HEALS was launched with the aim of incorporating a series of novel technologies, data analysis, and modelling tools to efficiently support exposome studies in Europe. The authors have developed a framework of modelling tools for estimating the long-term external exposure of selected population groups to multiple stressors through different pathways. As the starting point, the stressors, including electromagnetic fields (EMF) and ultraviolet light (UV) through dermal uptake, phthalates (DEHP, DIDP, and DINP) through inhalation, as well as chromium, mercury, and lead through food intake, have been selected. The simulation for multiple stressors has been realised by developing a probabilistic model that integrates the micro-environment approach, time-activity patterns, and a life course trajectory model. The methodology has been applied to a selected sample of subjects enrolled in the Italian Twin Registry (ITR). The results show that long-term exposures to multiple stressors are affected by factors including age, gender, geographical location, and education level. The methods developed in this paper extended the temporal and spatial scales of exposure modelling in Europe. Moreover, the application of our methods provided a novel approach and crucial input data for future work on environment-wide association studies.

The Italian Twin Registry: An Update at 18 Years From Its Inception.

The Italian Twin Registry (ITR), established in 2001, is a population-based registry of voluntary twins. To date, it consists of approximately 29,000 twins who gave their consent to participate in the studies proposed by the ITR research group. The database comprises 11,500 monozygotic and 16,700 dizygotic twins resident throughout the country and belonging to a wide age range (from 0 to 95 years, mean 36.8 years). This article provides an overview of the recruitment strategies along with the major phenotypes investigated during an 18 years' research period. Over the years, several self-reported questionnaire data were collected, together with saliva/blood samples and measurements taken during in-person interviews or outpatient clinical examinations. Mental and behavioral phenotypes as well as atherosclerotic traits were studied in depth across different age groups. A birth cohort of twins was established and followed up. Novel research hypotheses are also being tested in ongoing projects. The ITR is involved in international studies in collaboration with other twin registries and represents a valuable resource for national and international research initiatives regarding a broad spectrum of health-related characteristics.

H3K4me1 marks DNA regions hypomethylated during aging in human stem and differentiated cells.

In differentiated cells, aging is associated with hypermethylation of DNA regions enriched in repressive histone post-translational modifications. However, the chromatin marks associated with changes in DNA methylation in adult stem cells during lifetime are still largely unknown. Here, DNA methylation profiling of mesenchymal stem cells (MSCs) obtained from individuals aged 2 to 92 yr identified 18,735 hypermethylated and 45,407 hypomethylated CpG sites associated with aging. As in differentiated cells, hypermethylated sequences were enriched in chromatin repressive marks. Most importantly, hypomethylated CpG sites were strongly enriched in the active chromatin mark H3K4me1 in stem and differentiated cells, suggesting this is a cell type-independent chromatin signature of DNA hypomethylation during aging. Analysis of scedasticity showed that interindividual variability of DNA methylation increased during aging in MSCs and differentiated cells, providing a new avenue for the identification of DNA methylation changes over time. DNA methylation profiling of genetically identical individuals showed that both the tendency of DNA methylation changes and scedasticity depended on nongenetic as well as genetic factors. Our results indicate that the dynamics of DNA methylation during aging depend on a complex mixture of factors that include the DNA sequence, cell type, and chromatin context involved and that, depending on the locus, the changes can be modulated by genetic and/or external factors.

Education in Twins and Their Parents Across Birth Cohorts Over 100 years: An Individual-Level Pooled Analysis of 42-Twin Cohorts.

Whether monozygotic (MZ) and dizygotic (DZ) twins differ from each other in a variety of phenotypes is important for genetic twin modeling and for inferences made from twin studies in general. We analyzed whether there were differences in individual, maternal and paternal education between MZ and DZ twins in a large pooled dataset. Information was gathered on individual education for 218,362 adult twins from 27 twin cohorts (53% females; 39% MZ twins), and on maternal and paternal education for 147,315 and 143,056 twins respectively, from 28 twin cohorts (52% females; 38% MZ twins). Together, we had information on individual or parental education from 42 twin cohorts representing 19 countries. The original education classifications were transformed to education years and analyzed using linear regression models. Overall, MZ males had 0.26 (95% CI [0.21, 0.31]) years and MZ females 0.17 (95% CI [0.12, 0.21]) years longer education than DZ twins. The zygosity difference became smaller in more recent birth cohorts for both males and females. Parental education was somewhat longer for fathers of DZ twins in cohorts born in 1990-1999 (0.16 years, 95% CI [0.08, 0.25]) and 2000 or later (0.11 years, 95% CI [0.00, 0.22]), compared with fathers of MZ twins. The results show that the years of both individual and parental education are largely similar in MZ and DZ twins. We suggest that the socio-economic differences between MZ and DZ twins are so small that inferences based upon genetic modeling of twin data are not affected.

Early respiratory infections: the role of passive smoking in gene-environment interaction.

This study aims to: (i) estimate genetic and environmental components of four early respiratory diseases and (ii) test if these components are modified by parental smoking exposure. Study subjects were 2068 Italian twins aged 3-17. We performed biometric modeling under the assumptions of the twin design. For bronchitis and bronchiolitis, variance was mostly explained by shared environment, with no modification effect by parental smoking. For pneumonia and wheezy bronchitis, shared environmental component was larger among passive smokers, while genetic component was predominant among non-smokers. In the etiology of pneumonia and wheezy bronchitis, parental smoking could be a major familial factor.