Dual-comb optical parametric oscillator in the mid-infrared based on a single free-running cavity.

We demonstrate a free-running single-cavity dual-comb optical parametric oscillator (OPO) pumped by a single-cavity dual-comb solid-state laser. The OPO ring cavity contains a single periodically-poled MgO-doped LiNbO3 (PPLN) crystal. Each idler beam has more than 245-mW average power at 3550 nm and 3579 nm center wavelengths (bandwidth 130 nm). The signal beams are simultaneously outcoupled with more than 220 mW per beam at 1499 nm and 1496 nm center wavelength. The nominal repetition rate is 80 MHz, while the repetition rate difference is tunable and set to 34 Hz. To evaluate the feasibility of using this type of source for dual-comb applications, we characterize the noise and coherence properties of the OPO signal beams. We find ultra-low relative intensity noise (RIN) below -158 dBc/Hz at offset frequencies above 1 MHz. A heterodyne beat note measurement with a continuous wave (cw) laser is performed to determine the linewidth of a radio-frequency (RF) comb line. We find a full-width half-maximum (FWHM) linewidth of around 400 Hz. Moreover, the interferometric measurement between the two signal beams reveals a surprising property: the center of the corresponding RF spectrum is always near zero frequency, even when tuning the pump repetition rate difference or the OPO cavity length. We explain this effect theoretically and discuss its implications for generating stable low-noise idler combs suitable for high-sensitivity mid-infrared dual-comb spectroscopy (DCS).

51-W average power, 169-fs pulses from an ultrafast non-collinear optical parametric oscillator.

We present a high power optical parametric oscillator (OPO) synchronously pumped by the second-harmonic of a modelocked 1030-nm thin-disk laser (TDL) oscillator. The OPO delivers an average power of 51.1 W around degeneracy (1030 nm) with a 10.2-MHz repetition-rate. After extra-cavity dispersion compensation using dispersive mirrors, we obtain a pulse duration of 169 fs, which is 4.6× shorter than the TDL pulse duration of 770 fs. The TDL has 250 W average power, which is converted to 215 W at the second-harmonic. Hence, the OPO exhibits a high photon conversion efficiency of 47% (ratio of signal photons to 515-nm pump photons). Moreover, the OPO generates a peak power of 26.2 MW, which is very similar to the 28.0-MW peak power of the TDL. To facilitate continuous tuning around degeneracy and convenient extraction of the pump and idler beams, the OPO is operated in a noncollinear configuration. A linear cavity configuration was chosen since it offers easy alignment and straightforward cavity length tuning. To the best of our knowledge, this source has the highest average power generated by any ultrafast OPO, and the shortest pulse duration for any >5-W OPO. This result is an important step to adding wavelength tunability to high power Yb-based laser sources without the complexity of either laser or parametric amplifier systems.

Evolution of the IgE and IgG repertoire to a comprehensive array of allergen molecules in the first decade of life.

BACKGROUND: In early childhood, the allergen-specific IgG repertoire is mainly directed to animal and vegetable food molecules and infrequently to airborne molecules. It is unknown whether this early pattern is maintained throughout childhood. OBJECTIVE: To investigate the evolution of IgG and IgE responses to a broad panel of allergenic molecules from birth to age 10 years. METHODS: We examined the sera collected between birth and age 10 years from participants in the German Multicentre Allergy Study, a birth cohort born in 1990. The IgE (cutoff ≥0.30 ISU) and IgG (cutoff ≥0.10 ISU) responses to 35 genuine allergenic molecules were measured with a multiplex microarray approach (ImmunoCAP ISAC™). RESULTS: IgE responses were mostly directed against a restricted group of airborne molecules, with a sequence and prevalence hierarchy (Phl p 1> Bet v 1> Fel d 1> Phl p 5> Der p 2> Der p 1) largely maintained over time. Conversely, the IgG repertoire was much broader, starting with animal foodborne, then spreading to vegetable foodborne and finally to airborne molecules. A strong and persistent IgG response to a given airborne molecule almost invariably preceded or accompanied an IgE response to that molecule. CONCLUSIONS: The evolution of IgG and IgE responses throughout childhood differs widely at population level. IgG responses are mostly directed to animal food allergens, while IgE responses are dominated by airborne allergens. However, a strong IgG response almost invariably precedes or accompanies the appearance of IgE to the same molecule in specifically sensitized subjects.

Early life travelling does not increase risk of atopic outcomes until 15 years: results from GINIplus and LISAplus.

BACKGROUND: Westernized lifestyle has been blamed for allergy epidemics. One of its characteristics is increased distances and frequency of travelling from early life onwards. Early life travelling to places which substantially differ from home environment in terms of climate, vegetation and food could increase the exposure to further unknown allergens and hence promote the development of allergies, but no epidemiological study has investigated this speculation. METHODS: Detailed data on travelling during the first 2 years of life as well as a range of atopic outcomes along with potential confounders up to age 15 years were collected prospectively within two large population-based multicentre German birth cohorts - GINIplus and LISAplus. Farthest travelling destination (within Germany; middle/northern/eastern Europe; southern Europe; outside Europe), total number of trips and their combination were considered as exposures. Six atopic outcomes were used: (1) doctor-diagnosed asthma, (2) doctor-diagnosed allergic rhinitis, (3) nose and eye symptoms, (4) sensitization to food allergens, (5) sensitization to indoor and (6) outdoor inhalant allergens. Longitudinal associations between each exposure and health outcome pair were analysed using generalized estimation equations (GEEs). RESULTS: The results of our longitudinal analyses of 5674 subjects do not support the research hypothesis that travelling abroad to different regions in Europe or beyond Europe and frequency of travelling increase prevalence of doctor-diagnosed asthma and allergic rhinitis, nose and eye symptoms and allergic sensitization up to 15 years of age. Furthermore, there was no indication of age-varying effects. CONCLUSIONS: Early life travelling does not seem to increase risk of atopic outcomes. Nevertheless, as we could not account for the type of visited environment or length of stay, these first findings should be interpreted with caution.

The German Infant Nutritional Intervention Study (GINI) for the preventive effect of hydrolyzed infant formulas in infants at high risk for allergic diseases. Design and selected results.

In the complex interaction between certain environmental factors and genetic disposition, the early allergen exposure plays a major role in the development of allergic diseases. In aiming to reduce the allergen burden for the infant at risk during early infancy, cow's milk protein hydrolysate infant formulas (hypoallergenic infant formulas) are appropriate alternatives to breastfeeding for primary allergy prevention. The German Infant Nutritional Intervention-Program (GINI) was supported for the first 3 years by the German Ministry for Education and Research (BMBF) (FKZ 01 EE 9401-4). It is a birth cohort which was primarily scheduled until the children were 3 years old. The aim of the prospective, randomized, double-blind intervention study was to investigate the impact of different cow's milk protein hydrolysate infant formulas in the first 4 - 6 months on the development of allergic diseases in children at risk due to at least one parent or biological sibling with a history of allergic disease. The allocation to one of the 4 intervention formulas (partial whey hydrolysate, extensive whey hydrolysate, extensive casein hydrolysate or standard cow's milk formula) was randomised and stratified by family history (single/biparental) and the respective obstetric clinic. Recruitment was carried out by the three clinical centers (Research Institute Marien-Hospital Wesel, Children's Department, Ludwigs-Maximilians-University Munich and Children's Department Technical University Munich) in 18 obstetric clinics between 01.09.1995 and 30.06.1998. Along with the intervention study a non-interventional, complementary observational cohort of children with or without allergy risk was recruited and followed by annual self-reporting parental questionnaires. The GINI intervention study (GINI-I, N = 2.252) and the non-interventional observation study (GINI-NI, N = 3.739) are combined in the population-based GINIplus study (see article J. Heinrich et al. in this journal). The results of the GINI intervention study confirm that, cow's milk protein hydrolysate infant formulas have a preventive effect on allergic manifestation compared with a standard cow's milk formula, until school age. However, the dimension of the effect is different between the formulas. This effect, which is mainly driven by the effect on atopic eczema, develops in the first months of life and persists without rebound. In the formula groups the cumulative incidence of atopic eczema until school age is reduced between 26% and 45% compared with standard cow's milk formula. A beneficial effect of the hydrolysate formulas on the respiratory manifestations asthma and rhinoconjunctivitis, however, could not be shown. By comparing the GINI intervention and non-intervention arm of the GINIplus study it was demonstrated, that a family history for allergy doubles the risk for eczema in the offspring. Early intervention with cow's milk protein hydrolysate infant formulas is able to substantially compensate this risk for eczema until the age of 6 years. In contrast, by randomization to standard cow's milk formula this risk showed a trend towards a higher incidence compared with children at risk from the non-intervention group. Thus, the results of the GINIplus study have contributed to answer some of the controversially discussed questions.

GINIplus and LISAplus - Design and selected results of two German birth cohorts about natural course of atopic diseases and their determinants.

The increasing prevalence of asthma, hay fever, and allergic sensitization in Western Germany after east-west division in 1949 and their rapid increase in East German children after re-unification in 1990 are strong indications for the role of life-style and/or environmental factors in the development of atopic diseases. Obviously, the perinatal period is crucial for priming the immune system. Therefore, explorations of determinants of atopic diseases need pregnancy or birth cohorts as the most appropriate epidemiological study designs. This review presents the design and selected results of the two German birth cohorts GINIplus and LISAplus. GINIplus and LISAplus recruited 5.991 and 3.097 healthy, term newborns, respectively, from Munich, Wesel, Leipzig, and Bad Honnef. Approximately 55% could be followed for the first 10 years. We analyzed the natural course of atopic diseases and the role of life-style, environmental, and genetic factors for disease onset, intermediate phenotypes, and genes involved in detoxification and oxidative stress. The results of these two large birth cohorts contributed substantially to the understanding of atopic diseases and their determinants.

Allergic manifestation 15 years after early intervention with hydrolyzed formulas--the GINI Study.

BACKGROUND: Data on the long-term impact of hydrolyzed formulas on allergies are scarce. OBJECTIVE: To assess the association between early intervention with hydrolyzed formulas in high-risk children and allergic outcomes in adolescence. METHODS: GINI trial participants (n = 2252) received one of four formulas in the first four months of life as breastmilk substitute if necessary: partial or extensive whey hydrolyzate (pHF-W, eHF-W), extensive casein hydrolyzate (eHF-C) or standard cow's milk formula (CMF) as reference. Associations between these formulas and the cumulative incidence and prevalence of parent-reported physician-diagnosed asthma, allergic rhinitis (AR) and eczema, as well as spirometric indices and sensitization, were examined using generalized linear models. RESULTS: Between 11 and 15 years, the prevalence of asthma was reduced in the eHF-C group compared to CMF (odds ratio (OR) 0.49, 95% confidence interval (CI) 0.26-0.89), which is consistent with the spirometric results. The cumulative incidence of AR was lower in eHF-C (risk ratio (RR) 0.77, 95% CI 0.59-0.99]) and the AR prevalence in pHF-W (OR 0.67, 95% CI 0.47-0.95) and eHF-C (OR 0.59, 95% CI 0.41-0.84). The cumulative incidence of eczema was reduced in pHF-W (RR 0.75, 95% CI 0.59-0.96) and eHF-C (RR 0.60, 95% CI 0.46-0.77), as was the eczema prevalence between 11 and 15 years in eHF-C (OR 0.42, 95% CI 0.23-0.79). No significant effects were found in the eHF-W group on any manifestation,nor was there an effect on sensitization with any formula. CONCLUSION: In high-risk children, early intervention using different hydrolyzed formulas has variable preventative effects on asthma, allergic rhinitis and eczema up to adolescence.

Associations between serum 25-hydroxyvitamin D and bone turnover markers in a population based sample of German children.

Severe vitamin D deficiency is known to cause rickets, however epidemiological studies and RCTs did not reveal conclusive associations for other parameters of bone health. In our study, we aimed to investigate the association between serum levels of 25(OH) vitamin D and bone turnover markers in a population-based sample of children. 25(OH)D, calcium (Ca), osteocalcin (OC), and ß-Crosslaps (ß-CTx) were measured in 2798 ten-year-old children from the German birth cohorts GINIplus and LISAplus. Linear regression was used to determine the association between bone turnover markers and 25(OH)D levels. 25(OH)D, OC, and ß-CTx showed a clear seasonal variation. A 10 nmol/l increase in 25(OH)D was significantly associated with a 10.5 ng/l decrease (p < 0.001) in ß-CTx after adjustment for design, sex, fasting status, time of blood drawn, BMI, growth rate, and detectable testosterone/estradiol. For OC alone no significant association with 25(OH)D was observed, whereas the ß-CTx-to-OC ratio was inversely associated with 25(OH)D (-1.7% change, p < 0.001). When stratifying the analyses by serum calcium levels, associations were stronger in children with Ca levels below the median. This study in school-aged children showed a seasonal variation of 25(OH)D and the bone turnover markers OC and ß-CTx. Furthermore a negative association between 25(OH)D and the bone resorption marker ß-CTx was observed.

Parental allergic disease before and after child birth poses similar risk for childhood allergies.

Whether the strength of associations between parental and child allergic diseases differs by whether the first onset of the parental disease is before or after a child's birth has never been examined and is the aim of this study. Yearly childhood asthma, allergic rhinitis, and eczema diagnoses were longitudinally regressed against the effect of a parental disease (pre- vs post-child birth) of the same type separately for each parent using generalized estimation equations. Both a maternal and paternal history of asthma were associated with childhood asthma prevalence up to 15 years of age. Effect estimates were similar for parental asthma with first onset before and after the birth of the child. The results for allergic rhinitis and eczema were less consistent. Parental allergic diseases with first onsets before and after the birth of a child both pose risks to childhood allergic disease in the offspring, especially for asthma.

Epidemiology of urticaria in infants and young children in Germany--results from the German LISAplus and GINIplus Birth Cohort Studies.

BACKGROUND: Although urticaria is considered one of the most frequent skin diseases, reliable epidemiologic data are scarce. OBJECTIVE: To evaluate the incidence and cumulative prevalence of urticaria in infants and children up to age of 10, to characterize the relationship of specific IgE levels (food and inhalative allergens) with urticaria, and to monitor the joint occurrence of urticaria with other diseases, such as eczema, asthma, and hay fever. METHODS: The study population consisted of two prospective birth cohort studies: the LISAplus and GINIplus studies. Information on physician-diagnosed urticaria, asthma, eczema, or hay fever was collected using self-administered questionnaires completed by the parents. Blood samples were drawn, and specific immunoglobulin E measured at 2 (only LISAplus), 6 and 10 yr of age. RESULTS: The incidence of urticaria was approximately 1% per year of age. The cumulative prevalence of urticaria in children up to the age of 10 yr was 14.5% for boys and 16.2% for girls. Cumulative prevalence of urticaria at the age of ten was significantly (p < 0.05) associated with allergic sensitization to peanut, soy, and wheat flour, but not with inhalant allergens. Both a parental history of atopy/urticaria and the children's diagnosis of asthma, eczema, and hay fever were strongly related (p < 0.0001) to the occurrence of urticaria. CONCLUSIONS: Urticaria is a frequent event during childhood, with highest incidence in infants and preschool children. Comorbidity with atopic disease is high.

Peer problems are associated with elevated serum leptin levels in children.

BACKGROUND: Leptin is thought to act as an important mediator in stress reactions. To date, no study has examined the association between psychological stress and leptin levels in children. This study aimed to assess the association between emotional symptoms and peer problems and serum leptin levels in children aged 10 years of the two population-based GINI-plus and LISA-plus birth cohorts. METHOD: Cross-sectional data from 2827 children aged 10 years were assessed with regard to leptin concentrations in serum and behavioral problems using the parent-reported Strengths and Difficulties Questionnaire (SDQ). Linear regression modeling was applied to determine the likelihood of elevated leptin levels in children with emotional symptoms and peer problems, controlling for socio-economic status (SES), body mass index (BMI), fasting serum leptin levels, pubertal development and sex hormones. RESULTS: We found that increases in emotional symptoms (exp ß adj = 1.03, s.e. = 0.02, p < 0.04) and peer problems (exp ß adj = 1.05, s.e. = 0.01, p = 0.0001) were significantly associated with higher serum leptin levels controlled for BMI and sociodemographic factors. Similar results were found when the fasting serum leptin sample was examined (exp ß adj = 1.08, s.e. = 0.04, p = 0.0294). Gender-stratified analyses showed a significant relationship between serum leptin and peer problems in girls (exp ß adj = 1.05, s.e. = 0.02, p = 0.03), and a borderline significant association in boys (exp ß adj = 1.04, s.e. = 0.02, p = 0.05). CONCLUSIONS: Children with peer problems have higher stress and eat more, acquire a higher body fat mass and thus, through increased leptin resistance, exhibit higher leptin levels.

Long-term exposure to traffic-related air pollution and insulin resistance in children: results from the GINIplus and LISAplus birth cohorts.

AIMS/HYPOTHESIS: Epidemiological studies that have examined associations between long-term exposure to traffic-related air pollution and type 2 diabetes mellitus in adults are inconsistent, and studies on insulin resistance are scarce. We aimed to assess the association between traffic-related air pollution and insulin resistance in children. METHODS: Fasting blood samples were collected from 397 10-year-old children in two prospective German birth cohort studies. Individual-level exposures to traffic-related air pollutants at the birth address were estimated by land use regression models. The association between air pollution and HOMA of insulin resistance (HOMA-IR) was analysed using a linear model adjusted for several covariates including birthweight, pubertal status and BMI. Models were also further adjusted for second-hand smoke exposure at home. Sensitivity analyses that assessed the impact of relocating, study design and sex were performed. RESULTS: In all crude and adjusted models, levels of insulin resistance were greater in children with higher exposure to air pollution. Insulin resistance increased by 17.0% (95% CI 5.0, 30.3) and 18.7% (95% CI 2.9, 36.9) for every 2SDs increase in ambient NO2 and particulate matter ≤10 µm in diameter, respectively. Proximity to the nearest major road increased insulin resistance by 7.2% (95% CI 0.8, 14.0) per 500 m. CONCLUSIONS/INTERPRETATION: Traffic-related air pollution may increase the risk of insulin resistance. Given the ubiquitous nature of air pollution and the high incidence of insulin resistance in the general population, the associations examined here may have potentially important public health effects despite the small/moderate effect sizes observed.

Early life risk factors of being overweight at 10 years of age: results of the German birth cohorts GINIplus and LISAplus.

OBJECTIVE: To develop a prediction model that quantifies the risk of being overweight at 10 years of age. SUBJECTS/METHODS: In total, 3121 participants from the GINIplus (German Infant Nutritional Intervention plus environmental and genetic influences on allergy development) and LISAplus (Influences of Lifestyle-Related Factors on the Immune System and the Development of Allergies in Childhood plus Air Pollution and Genetics) German birth cohorts were recruited. We predicted standardized body mass index (BMI) at 10 years of age using standardized BMIs from birth to 5 years. Parental education, family income and maternal smoking during pregnancy were considered as covariates. Linear and logistic regression models were used to evaluate the impact of risk factors on BMI and on being overweight at 10 years of age, respectively. RESULTS: Birth weight, standardized BMI at 5 years (60-64 months) (ß=0.77; 95% confidence interval (CI): 0.73-0.81) and maternal smoking during pregnancy were positively associated with standardized BMI at 10 years of age. Standardized BMI and overweight at 5 years were strongest predictors of being overweight at 10 years. Conversely, high parental education conferred a protective effect (ß=-0.15; 95% CI: -0.29 to -0.01). Being overweight at 5 years (60-64 months) increased the risk of being overweight at 10 years of age with odds ratios above 10. Among children who were predicted to be overweight at 10 years, cross-validation results showed that 76.8% of female subjects and 68.1% of male subjects would be overweight at 10 years of age. CONCLUSION: BMI and being overweight at 5 years of age are strong predictors of being overweight at 10 years of age. The effectiveness of targeted interventions in children who are overweight at 5 years of age should be explored.

German national consensus recommendations on nutrition and lifestyle in pregnancy by the 'Healthy Start - Young Family Network'.

Diet and physical activity before and during pregnancy affect short- and long-term health of mother and child. The energy needs at the end of pregnancy increase only by about 10% compared to nonpregnant women. An excessive energy intake is undesirable since maternal overweight and excessive weight gain can increase the risks for a high birth weight and later child overweight and diabetes. Maternal weight at the beginning of pregnancy is especially important for pregnancy outcome and child health. Women should strive to achieve normal weight already before pregnancy. Regular physical activity can contribute to a healthy weight and to the health of pregnant women. The need for certain nutrients increases more than energy requirements. Before and during pregnancy, foods with a high content of essential nutrients should be preferentially selected. Supplements should include folic acid and iodine, iron (in case of suboptimal iron stores), the ω-3 fatty acid docosahexaenoic acid (in case of infrequent consumption of ocean fish) and vitamin D (in case of decreased sun exposure and decreased endogenous vitamin D synthesis). Pregnant women should not smoke and not stay in rooms where others smoke or have smoked before (passive smoking). Alcohol consumption should be avoided, since alcohol can harm unborn children.

[Nutrition in pregnancy - Practice recommendations of the Network "Healthy Start - Young Family Network"]. / Ernährung in der Schwangerschaft - Teil 1.

Nutrition, physical activity and lifestyle in pregnancy influence maternal and child health. The "Healthy start - Young Family Network" supported by the German Government with the national action plan IN FORM developed recommendations on nutrition in pregnancy. Energy needs increase by only ≈10 % by the end of pregnancy whereas micronutrient needs increase much more. Normal weight should preferably be achieved before pregnancy. Dietary recommendations follow those for the general population. Folic acid supplements (400 µg/day) should be started before pregnancy and continue for at least the first trimester. Iodine rich foods and salt and an iodine supplement (100-150 µg/day) are recommended. Long-chain omega-3 fatty acids should be provided with ≥ 1 weekly portion of oily sea fish, or a DHA-supplement if regular fish consumption is avoided. Vitamin D supplementation is advisable unless there is regular exposure to sunlight. Health care professions should lead parents to health-promoting lifestyles. Subjects of part 2 of the article are practice recommendations on nutrition in pregnancy, especially vegetarian diets, recommendations on micronutrient supplementation, risk reduction of listeriosis and toxoplasmosis, alcohol, tobacco, caffeine and physical activity in pregnancy.

[Nutrition in pregnancy - Practice recommendations of the Network "Healthy Start - Young Family Network"]. / Ernährung in der Schwangerschaft - Teil 2. Handlungsempfehlungen des Netzwerks "Gesund ins Leben - Netzwerk Junge Familie".

Nutrition, physical activity and lifestyle in pregnancy influence maternal and child health. The "Healthy start - Young Family Network" supported by the German Government with the national action plan IN FORM developed recommendations on nutrition in pregnancy. Folic acid supplements (400 µg/day) should be started before pregnancy and continue for at least the first trimester. Iodine rich foods and salt and an iodine supplement (100-150 µg/day) are recommended. Long-chain omega-3 fatty acids should be provided with ≥ 1 weekly portion of oily sea fish, or a DHA-supplement if regular fish consumption is avoided. Vitamin D supplementation is advisable unless there is regular exposure to sunlight. Iron supplements should be used based on medical history and blood testing. Vegetarian diets with nutritional supplements can provide adequate nutrition, but counselling is recommended. In contrast, a vegan diet is inadequate and requires additional micronutrient supplementation. For risk reduction of listeriosis and toxoplasmosis, raw animal foods, soft cheeses and packed fresh salads should be avoided; fresh fruit, vegetables and salad should be washed well and consumed promptly. Pregnant women should remain physically active and perform sports with moderate intensity. They should avoid alcohol, active and passive smoking. Up to 3 daily cups of coffee are considered harmless, but energy drinks should be avoided. Childhood allergy is not reduced by avoiding certain foods in pregnancy whereas oily sea fish is recommended. Health care professions should lead parents to health-promoting lifestyles. Subjects of part 1 of the article are practice recommendations on nutrition, on energy needs, micronutrient needs and body weight/weight gain in pregnancy.

[Two German Birth Cohorts: GINIplus and LISAplus]. / Die zwei deutschen Geburtskohorten GINIplus und LISAplus.

Numerous chronic diseases in childhood and adulthood have their origins in perinatal life and are potentially influenced by trans-generational epigenetic processes. Therefore, prospective birth cohorts can substantially contribute to our knowledge about the etiology of diseases including modifiable risk factors. The two population-based German birth cohorts GINIplus and LISAplus aim to describe the natural course of chronic diseases and intermediate phenotypes in childhood and its determinants, and to identify potential genetic effect modifications. In the mid-1990s, 5,991 (GINIplus) and 3,097 (LISAplus) healthy, term newborns were recruited for long-term follow-up in four regions of Germany. The follow-up rate for the first 10 years was about 55%. We analyzed the growth and development of overweight, infections and allergic diseases, mental and oral health, metabolic and inflammatory parameters and the role of potential risk factors including genetics. The results of these two birth cohorts substantially contribute to the current knowledge about the natural course of these health parameters. These data were included in many international projects and consortia for purposes of international comparisons of prevalence and consistency of findings, and to increase the power of the analyses.

Association of gas cooking with children's respiratory health: results from GINIplus and LISAplus birth cohort studies.

UNLABELLED: Previous studies have found inconsistent results on the association between asthma in children and gas cooking emissions. We aimed to assess the effects of the long-term exposure to gas cooking on the onset of asthma and respiratory symptoms, focusing on wheezing, in children from two German birth cohorts: LISAplus and GINIplus. A total of 5078 children were followed until the age of 10 years. Asthma, wheezing, gas cooking, and exposure to other indoor factors were assessed through parental reported questionnaires administered periodically. Logistic and multinomial regressions adjusting for potential confounders were performed. The prevalence of asthma and persistent wheezing was higher among children exposed to gas cooking but the results were not statistically significant. Exposure to gas cooking was positively associated (P-value < 0.05) with exposure to other indoor factors (dampness, environmental tobacco smoke, and pets). Our results did not show a statistically significant association between the exposure to gas cooking and children's respiratory health. PRACTICAL IMPLICATIONS: These analyses are consistent with the assumption of no effect of the exposure to low doses of nitrogen dioxide. The strong positive associations found between gas cooking and other indoor factors highlight the importance of considering other indoor factors when assessing health effects of gas cooking. Low-dose exposure to indoor nitrogen dioxide through gas cooking might not contribute to increase the risk of asthma and respiratory symptoms in children.

Growth velocity during infancy and onset of asthma in school-aged children.

BACKGROUND: Growth velocities during infancy might affect the risk of asthma in childhood. This study examines the association between peak height and weight velocities during the first 2 years of life and onset of asthma and wheeze up to 10 years of age. METHODS: Data from 9086 children who participated in the GINIplus and LISAplus birth cohorts were analyzed. Information on asthma was requested annually from 1 to 10 years and information on wheeze at 1, 2, 4, 6, and 10 years. Peak height and weight velocities were calculated using height and weight measurements obtained between birth and 2 years of age. Cox proportional hazards models and generalized linear mixed models were calculated after adjustment for potential confounding factors including birth weight and body mass index at 10 years of age. RESULTS: Per interquartile range increase in peak weight velocity (PWV), the risk of asthma increased significantly (adjHR: 1.22; CI: 1.02-1.47). The relationship between peak height velocity (PHV) and onset of asthma was nonsignificant (adjHR: 1.08; CI: 0.88-1.31). Wheeze was not significantly associated with PHV or with PWV (adjOR: 1.07; CI: 0.64-1.77 and adjOR: 1.11; CI: 0.68-1.79, respectively). CONCLUSIONS: Weight gain during infancy is positively associated with physician-diagnosed asthma in school-aged children.