Health of singleton neonates in Switzerland through time and crises: a cross-sectional study at the population level, 2007-2022.

BACKGROUND: Being exposed to crises during pregnancy can affect maternal health through stress exposure, which can in return impact neonatal health. We investigated temporal trends in neonatal outcomes in Switzerland between 2007 and 2022 and their variations depending on exposure to the economic crisis of 2008, the flu pandemic of 2009, heatwaves (2015 and 2018) and the COVID-19 pandemic. METHODS: Using individual cross-sectional data encompassing all births occurring in Switzerland at the monthly level (2007-2022), we analysed changes in birth weight and in the rates of preterm birth (PTB) and stillbirth through time with generalized additive models. We assessed whether the intensity or length of crisis exposure was associated with variations in these outcomes. Furthermore, we explored effects of exposure depending on trimesters of pregnancy. RESULTS: Over 1.2 million singleton births were included in our analyses. While birth weight and the rate of stillbirth have remained stable since 2007, the rate of PTB has declined by one percentage point. Exposure to the crises led to different results, but effect sizes were overall small. Exposure to COVID-19, irrespective of the pregnancy trimester, was associated with a higher birth weight (+12 grams [95% confidence interval (CI) 5.5 to 17.9 grams]). Being exposed to COVID-19 during the last trimester was associated with an increased risk of stillbirth (odds ratio 1.24 [95%CI 1.02 to 1.50]). Exposure to the 2008 economic crisis during pregnancy was not associated with any changes in neonatal health outcomes, while heatwave effect was difficult to interpret. CONCLUSION: Overall, maternal and neonatal health demonstrated resilience to the economic crisis and to the COVID-19 pandemic in a high-income country like Switzerland. However, the effect of exposure to the COVID-19 pandemic is dual, and the negative impact of maternal infection on pregnancy is well-documented. Stress exposure and economic constraint may also have had adverse effects among the most vulnerable subgroups of Switzerland. To investigate better the impact of heatwave exposure on neonatal health, weekly or daily-level data is needed, instead of monthly-level data.

Age at menarche, environmental stress, and social inequality: Evidence from Poland in the 1930s-1950s.

OBJECTIVE: To address the relationship between socioeconomic factors and age of menarche among Polish women born and reared in periods that varied considerably in environmental stresses: the Great Depression of the 1930s, the interval of World War II, and the interval of communist rule following World War II through the 1950s. METHODS: The data set included information on age at menarche and socioeconomic status (SES) of 718 women born during the Great Depression (n = 182), WWII (n = 189), and post-WWII through the 1950s (n = 347). A structured semi-parametric statistical model (generalized additive model [GAM] class) was used for analysis. An ANOVA-like linear model was used to test for marginal effects of SES-related factors and their interactions together with nonparametric seasonal effect. RESULTS: The influence of period of birth, month of birth, region of early childhood, and father's education, and the interaction between period of birth and father's education on age at menarche were statistically significant. During the economic crisis and the interval of WWII, differences in ages at menarche between the extreme categories of father's education were marked. The differences in ages at menarche between women from the lowest and highest social groups were markedly reduced among women born during the post-war interval. In addition, women born in February-March attained menarche earlier than women born in September-October. CONCLUSIONS: Unpredictable conditions associated with the economic crisis and war conditions had a stronger impact on age at menarche among women from families of lower SES compared to women from better economic circumstances. Individuals born and reared in low SES conditions likely suffered more severe deterioration across the spectrum of the standard of living and quality of life compared to those with a higher SES.

Body mass index in young men in Switzerland after the national shutdowns during the COVID-19 pandemic: results from a cross-sectional monitoring study at the population level since 2010.

BACKGROUND: Owing to the coronavirus disease pandemic, the Swiss goverment imposed a shutdown twice in 2020, which may have changed diet and physical activity. Regarding the question of weight change during the pandemic, little information based on measured weight data is available. We aimed to investigate whether the body mass indices (BMIs) of young Swiss men after the two shutdowns in spring and fall 2020 differed from those of young men examined before the shutdowns. METHODS: We analysed young Swiss men's BMIs taken during mandatory recruitment for the Swiss Armed Forces at the cross-sectional (not individual longitudinal) monitoring level and across weeks of conscription between January 2010 and July 2021 (n = 373 016). These data allow for continuous health monitoring of young men at almost the population level (coverage, >90%). For statistical modelling, we used the generalized additive model (GAM) framework. RESULTS: We showed that the BMIs of the conscripts examined in the 15 weeks after the two shutdowns in spring and autumn 2020 were not or only slightly different from their baseline values. Sensitivity analyses revealed that this conclusion also holds if the BMI distribution or prevalence of excess weight is assessed. The GAM further showed the significant effects of individual and area-based measures of socioeconomic position and age on BMI. CONCLUSION: Our results suggest that lifestyle changes during the pandemic in young men might have been too modest to be reflected in body weight. However, longitudinal data and/or data on women, children, or the elderly may lead to different conclusions.

Childhood respiratory allergies and symptoms in highly polluted area of Central Europe.

The study investigated the associations between the prevalence of the childhood respiratory diseases and the long-term exposure to air pollution in the burdened area of Moravian-Silesian Region in the Czech Republic. The health data were collected during 2014 in 7,239 children 5, 9, 13 and 17 years of age. Exposure to PM10 and NO2 in the residence addresses was based on dispersion models and GIS based traffic-related indicators. PM10 levels were positively associated with both lifetime (OR 1.35; 95%CI 1.09-1.67) and current (OR 1.32; 95%CI 1.05-1.67) allergic rhinitis; current asthma was associated negatively. The associations between traffic indicator and respiratory health were not found. On the other hand, marked positive associations were found between the respiratory diseases and symptom severity structured into ordinal variables, and PM10 and NO2. Modelled long-term exposure to air pollution was associated with childhood allergic rhinitis and deterioration of the respiratory symptoms.

Birth seasons and heights among girls and boys below 12 years of age: lasting effects and catch-up growth among native Amazonians in Bolivia.

BACKGROUND: Seasons affect many social, economic, and biological outcomes, particularly in low-resource settings, and some studies suggest that birth season affects child growth. AIM: To study a predictor of stunting that has received limited attention: birth season. SUBJECTS AND METHODS: This study uses cross-sectional data collected during 2008 in a low-resource society of horticulturists-foragers in the Bolivian Amazon, Tsimane'. It estimates the associations between birth months and height-for-age Z-scores (HAZ) for 562 girls and 546 boys separately, from birth until age 11 years or pre-puberty, which in this society occurs ∼13-14 years. RESULTS: Children born during the rainy season (February-May) were shorter, while children born during the end of the dry season and the start of the rainy season (August-November) were taller, both compared with their age-sex peers born during the rest of the year. The correlations of birth season with HAZ were stronger for boys than for girls. Controlling for birth season, there is some evidence of eventual partial catch-up growth, with the HAZ of girls or boys worsening until ∼ age 4-5 years, but improving thereafter. By age 6 years, many girls and boys had ceased to be stunted, irrespective of birth season. CONCLUSION: The results suggest that redressing stunting will require attention to conditions in utero, infancy and late childhood.

The variability of automated QRS duration measurement.

AIMS: Previous studies have demonstrated substantial variability in manual assessment of QRS complex duration (QRSd). Disagreements in QRSd measurements were also found in several automated algorithms tested on digitized electrocardiogram (ECG) recordings. The aim of our study was to investigate the variability of automated QRSd measurements performed by two commercially available electrocardiographs. METHODS AND RESULTS: Two GE MAC 5000 (GE-1 and GE-2) electrocardiographs and two Mortara ELI 350 (Mortara-1 and Mortara-2) electrocardiographs were used in the study. Participants for the study were recruited from patients hospitalized in the department of cardiology of a university hospital. Participants underwent up to four recording sessions within a single day with a different electrocardiograph at each session when two to four immediately successive ECG recordings were undertaken. In 76 patients, 683 ECGs were recorded; the mean QRSd was 109.0 ± 26.1 ms. The QRSd difference ≥10 ms between the first and second intra-session ECG was found in 7, 3, 20, and 14% of ECG pairs for GE-1, GE-2, Mortara-1, and Mortara-2, respectively. No inter-session difference in QRSd was found within both manufacturers. In individual patients, Mortara calculated the mean QRSd to be longer by 7.3 ms (95% CI: 6.2-8.5 ms, P < 0.0001) with a 2.1-times (95% CI: 1.9-2.4) greater standard deviation of the mean QRSd (7.1 vs. 3.3 ms, P < 0.001). CONCLUSION: Electrocardiographs from two manufacturers measured QRSd values with a systematic difference and a significantly different level of precision. This may have important clinical implications in selection of suitable candidates for cardiac resynchronization therapy.

Body parameters of Czech breastfed children compared to the Czech references and WHO growth standards.

BACKGROUND: The study concerns the comparison of percentile curves of Czech breastfed children with Czech national references from 1991 and 2001 and WHO growth standards. Growth charts of breastfed children demonstrate different curve shapes, especially in the first months of life. Incorrect interpretation of the growth curve could lead to premature introduction of complementary foods or infant formula. AIM: The comparison of four body parameters of Czech breastfed children with currently used Czech national references and WHO standards in order to recommend that Czech paediatricians use either Czech references or WHO standards in their practice. SUBJECTS AND METHODS: Nine hundred and sixty breastfed children were included in the study of length-for-age, head circumference-for-age, weight-for-age and weight-for-length parameters. All percentile curves were compared. Values of the 50th percentile expressed in z-scores based on both Czech references and WHO standards were tested. RESULTS: The study confirmed results of previous surveys documenting that growth of breastfed children is specific. Nevertheless, percentile curves of growth parameters of Czech breastfed children are closer to Czech references than WHO standards. CONCLUSIONS: The Czech national references fulfil the needs of Czech paediatricians (with pointing to specifics of breastfed child growth) and WHO standards are suitable, especially for international comparison.

Increased tissue and circulating levels of dipeptidyl peptidase-IV enzymatic activity in patients with pancreatic ductal adenocarcinoma.

BACKGROUND/OBJECTIVES: Pancreatic ductal adenocarcinoma (PDAC) is frequently heralded by an impairment of glucose homeostasis. Dipeptidyl peptidase-IV (DPP-IV) and fibroblast activation protein alpha (FAP) are aminopeptidases that regulate several bioactive peptides involved in glucoregulation, and are frequently dysregulated in cancer. The present study analyzes blood plasma levels and the quantity and localization of DPP-IV and FAP in PDAC tissues. METHODS: DPP-IV and FAP concentration and enzymatic activity were evaluated in the plasma from 93 PDAC, 39 type 2 diabetes mellitus (T2DM) and 29 control subjects, and in matched paired non-tumorous and tumor tissues from 48 PDAC patients. The localization of DPP-IV and FAP was determined using immunohistochemistry and catalytic histochemistry. RESULTS: The enzymatic activity and concentration of DPP-IV was higher in PDAC tumor tissues compared to non-tumorous pancreas. DPP-IV was expressed in cancer cells and in the fibrotic stroma by activated (myo)fibroblasts including DPP-IV(+)FAP(+) cells. FAP was expressed in stromal cells and in some cancer cells and its expression was increased in the tumors. Plasmatic DPP-IV enzymatic activity, and in particular the ratio between DPP-IV enzymatic activity and concentration in PDAC with recent onset DM was higher compared to T2DM. In contrast, the plasmatic FAP enzymatic activity was lower in PDAC compared to T2DM and controls and rose after tumor removal. CONCLUSIONS: DPP-IV-like enzymatic activity is upregulated in PDAC tissues. PDAC patients with recent onset diabetes or prediabetes have increased plasmatic DPP-IV enzymatic activity. These changes may contribute to the frequently observed association of PDAC and recent onset impairment of glucoregulation.

Growth of Czech breastfed infants in comparison with the World Health Organization standards.

Growth references are important for paediatric health monitoring. It is critical to understand differences in growth interpretation and potential consequences when using available growth references. This study compares the growth of Czech breastfed children with the current WHO growth standards 2006 and the Czech references 1991, 2001. A total of 960 infant/parent pairs in the Czech Republic were recruited through paediatric practices. Anthropometric data were collected during infants' first 12 months of life and parent questionnaires were gathered during a preventive visit at 18 months. Czech breastfed infants were longer with a greater head circumference at all percentiles compared to the WHO standards and were similar to the national references. The percentile weight-for-age and weight-for-length values of infants (: 6 months) were lower, and higher (6-12 months) compared to the WHO standards. The infant growth in the sample differed from both the WHO standards as well as the national references. Our findings indicate that the growth of Czech breastfed children differs from the current national references. These discrepancies were smaller compared to the WHO standards. The results of the study were used for new growth assessment guidelines to optimize feeding recommendations for Czech infants. The adoption of the WHO standards in the Czech Republic is not recommended.

Asthma Exacerbations and Symptom Variability in Children Due to Short-term Ambient Air Pollution Changes in Ostrava, Czech Republic.

AIM: The Ostrava region suffers from high levels of air pollution during winter inversions. We investigated the association between short-term elevations of air pollutant concentrations and worsening of respiratory problems, use of asthma medication and restriction of daily activities in asthmatic patients in Ostrava. METHODS: One-hundred and forty-seven child and adolescent patients (aged 6-18 years) with a confirmed diagnosis of mild to moderate persistent asthma were included in the study. Participants' parents completed diaries covering the period of November 2013 to February 2014; this analysis included 18,228 person-days. Daily smoothed maps of outdoor concentrations of particulate matter (PM10), nitrogen dioxide (NO2) and sulphur dioxide (SO2) were constructed from routine monitoring data, and participants' daily exposures were estimated on the basis of time spent at home and at school. The associations between health outcomes and exposure to air pollutants were estimated using the multiple logistic regression method. RESULTS: The odds ratios (OR) of the combined outcome for wheezing and/or difficulty in breathing, per 10 µg/m³ increase in the mean 24-h exposure were 1.07 (95% confidence interval 1.04-1.11) for PM10, 1.30 (1.18-1.44) for NO2, and 1.37 (1.18-1.59) for SO2. Additional inhaler use (in addition to usual medication) was also more frequent at higher air pollutant concentrations; the odds ratios per 10 µg/m³ increase in the mean 24-h exposure were 1.05 (1.02-1.07) for PM10, 1.19 (1.10-1.30) for NO2, and 1.26 (1.11-1.43) for SO2. Associations were less consistent for other health outcomes. CONCLUSIONS: These results suggest moderately strong associations between air pollutant concentrations and respiratory difficulties among asthmatic children and adolescents. More detailed analyses are required to confirm these preliminary findings.

Major ions in Central European precipitation - Insight into changes in NO3-/SO42-, NH4+/NO3- and NH4+/SO42- ratios over the last four decades.

Knowledge of precipitation composition is important, among other things, to reveal changes in atmospheric chemistry. Here we present the long-term time trends in ratios of major ions in precipitation, namely nitrate to sulphate (NO3-/SO42-), ammonium to sulphate (NH4+/SO42-) and ammonium to nitrate (NH4+/NO3-). For this we explore the long-term time series recorded by the Czech Hydrometeorological Institute at eight monitoring sites situated in urban, rural and mountain regions of the Czech Republic between 1980 and 2020. To that end, we use innovative Bayesian inference with the Integrated Nested Laplace Approximation (INLA) computational method appropriate for investigating complicated large-scale data. Our results indicated: (i) increasing NO3-/SO42- ratio in precipitation over time and distinct seasonal behaviour with higher values in winter and lower values in summer, (ii) increasing NH4+/SO42- ratio in precipitation and distinct seasonal behaviour with higher values in summer and lower values in winter and (iii) relatively stable NH4+/NO3- ratio in precipitation with a mild recent increase and distinct seasonal behaviour with higher values in summer and lower values in winter. This behaviour pattern holds true for all the sites analysed, irrespective of their geographical position, altitude or environment. Though explored in detail rarely, the ion ratios are important to study as they reflect changes in atmospheric chemistry, mirroring changes in emissions and meteorology and suggesting changing impacts on ecosystems and the environment.

Toxicokinetic relationship between the adducts in globin and their cleavage products in the urine: Implications for human biomonitoring.

Globin adducts of various chemicals, persisting in organism over the whole lifetime of erythrocytes, have been used as biomarkers of cumulative exposures to parent compounds. After removal of aged erythrocytes from the bloodstream, cleavage products of these adducts are excreted with urine as alternative, non-invasively accessible biomarkers. In our biomonitoring studies on workers exposed to ethylene oxide, its adduct with globin, N-(2-hydroxyethyl)valine, and the related urinary cleavage product N-(2-hydroxyethyl)-L-valyl-L-leucine have been determined. To describe a toxicokinetic relationship between the above types of biomarkers, a general compartmental model for simulation of formation and removal of globin adducts has been constructed in the form of code in R statistical computing environment. The essential input variables include lifetime of erythrocytes, extent of adduct formation following a single defined exposure, and parameters of exposure scenario, while other possible variables are optional. It was shown that both biomarkers reflect the past exposures differently as the adduct level in globin is a mean value of adduct levels across all compartments (subpopulations of erythrocytes of the same age) while excretion of cleavage products reflects the adduct level in the oldest compartment. Application of the model to various scenarios of continuous exposure demonstrated its usefulness for human biomonitoring data interpretation.

Ambient temperature-related sex ratio at birth in historical urban populations: the example of the city of Poznan, 1848-1900.

This study examines whether exposure to ambient temperature in nineteenth-century urban space affected the ratio of boys to girls at birth. Furthermore, we investigate the details of temperature effects timing upon sex ratio at birth. The research included 66,009 individual births, aggregated in subsequent months of births for the years 1847-1900, i.e. 33,922 boys and 32,087 girls. The statistical modelling of the probability of a girl being born is based on logistic GAM with penalized splines and automatically selected complexity. Our research emphasizes the significant effect of temperature in the year of conception: the higher the temperature was, the smaller probability of a girl being born was observed. There were also several significant temperature lags before conception and during pregnancy. Our findings indicate that in the past, ambient temperature, similar to psychological stress, hunger, malnutrition, and social and economic factors, influenced the viability of a foetus. Research on the effects of climate on the sex ratio in historical populations may allow for a better understanding of the relationship between environmental factors and reproduction, especially concerning historical populations since due to some cultural limitations, they were more prone to stronger environmental stressors than currently.

Ambient ozone at a rural Central European site and its vertical concentration gradient close to the ground.

The representativeness of ambient air quality of an in situ measurement is key in the use and correct interpretation of the measured concentration values. Though the horizontal representativeness aspect is generally not neglected in air pollution studies, a detailed, high-resolution vertical distribution of ambient air pollutant concentrations is rarely addressed. The aim of this study is twofold: (i) to explore the vertical distribution of ground-level ozone (O3) concentrations measured at four heights above the ground-namely at 2, 8, 50, and 230 m-and (ii) to examine in detail the vertical O3 concentration gradient in air columns between 2 and 8, 8 and 50, and 50 and 230 m above the ground. We use the daily mean O3 concentrations measured continuously at the Kosetice station, representing the rural Central European background ambient air quality observed during 2015-2021. We use the semiparametric GAM (generalised additive model) approach (with complexity or roughness-penalised splines implementation) to analyse the data with sufficient flexibility. Our models for both O3 concentrations and O3 gradients use (additive) decomposition into annual trend and seasonality (plus an overall intercept). The seasonal and year-to-year patterns of the modelled O3 concentrations look very similar at first glance. Nevertheless, a more detailed look through O3 gradients shows that they differ substantially with respect to their seasonal and long-term dynamics. The vertical O3 concentration gradient in 2-230 m is not uniform but changes substantially with increasing height and shows by far the highest dynamics near the ground between 2 and 8 m, differing in both the seasonal and annual aspects for all the air columns inspected. We speculate that non-linear changes of both seasonal and annual components of vertical O3 gradients are due to atmospheric-terrestrial interactions and to meteorological factors, which we will explore in a future study.

From little girls to adult women: Changes in age at marriage in Scheduled Castes from Madhya Pradesh and Uttar Pradesh, India.

BACKGROUND: Research confirms the negative relationship between early marriage and mothers' and children's health outcomes. This is why studies of the changes in age at marriage are an important task from the point of view of the health status and well-being of a mother and her offspring, especially in groups represented by extremely disadvantaged social strata in India. The results of such studies may influence the future family planning policy in the country. OBJECTIVES: This study aims to investigate the trend of age at marriage among the Scheduled Castes (SCs) women from two Indian states: Madhya Pradesh and Uttar Pradesh relative to the level of education and also to socioeconomic changes in the states. These states manifest the highest proportion of girls getting married below the age of 18 years-far above the proportion observed in entire India. METHODS: Women from Scheduled Caste, N = 1,612, aged 25-65, born in 1950-1990 were investigated. A modern semiparametric regression approach was used. To capture the relationship between age at marriage and year of birth, categories of women's level of education (illiterate; primary: 1st-5th standards; middle school: 6th-8th standards; high school: 9th-10th standards; higher secondary: 11th-12th standards), and categories of the profession (women working in the agricultural sector or the non-agricultural sector), flexible framework of the Generalized Additive Model (GAM) was applied. RESULTS: A significant impact of the cohort defined by the year of birth (<0.001), and women's education (<0.001) on age at marriage was noted, while the influence of women's occupation was not significant (p = 0.642). Mean age at marriage differed significantly with different education level. Women who graduated from primary school married 0.631 years later on average than illiterate ones, while those who graduated from middle schools, high schools (9th-10th standards) and higher secondary schools married significantly later than illiterate ones by 1.454 years and 2.463 years, respectively. Age at marriage increased over time: from slightly above 15 years in the cohort of illiterate women born in 1950 to almost 19 years in quite well-educated women born in 1990. The average age at marriage estimated for four education levels in 1990 ranged between 16.39 years (95%CI: 15.29-17.50) in the group of illiterate women and 18.86 years (95%CI: 17.76-19.95) in women graduated from high and higher secondary schools. CONCLUSION: The rise of age at marriage can be partly explained by the increase of females enrolled in schools, the alleviation of poverty, and the implementation of social programs for women.

Dynamics of glucose concentration during the initiation of ketogenic diet treatment in children with refractory epilepsy: Results of continuous glucose monitoring.

OBJECTIVE: The ketogenic diet (KD) is a diet low in carbohydrates and rich in fats which has long been used to treat refractory epilepsy. The metabolic changes related to the KD may increase the risk of hypoglycemia, especially during the first days. The study focused on the impact of KD initiation on glycemia in non-diabetic patients with refractory epilepsy. METHODS: The subjects were 10 pediatric patients (6 boys, mean age 6.1 ± 2.4 years), treated for intractable epilepsy. Blinded continuous glucose monitoring system (CGM) Dexcom G4 was used. Patients started on their regular diet in the first 36 hours of monitoring, followed by an increase in lipids intake and a gradual reduction of carbohydrates (relations 1:1; 2:1; 3:1; 3.5:1). We analyzed changes in glycemia during fat: nonfat ratio changes using a generalized linear model. RESULTS: The mean monitored time per person was 6 days, 10 hours and 44 minutes. The mean ± SD glycemia for the regular diet was 4.84 ± 0.20 mmol/L, for the carbohydrates/fat ratio of 1:1 it was 4.03 ± 0.16, for the ratio of 2:1 it was 3.57 ± 0.10, for the ratio 3:1 it was 3.39 ± 0.13 and for the final ratio of 3.5:1 it was 2.79 ± 0.06 mmol/L (P < 0.001). The portions of time spent in glycemia ≤3.5 mmol/L (≤2.5 mmol/L respectively) were: on the normal diet 0.88% (0.31%) of the monitored period, during 1:1 KD ratio 1.92% (0.95%), during 2:1 ratio 3.18% (1.02%), and during 3:1 and 3.5:1 ratios 13.64% (2.36%) of the monitored time (P < 0.05). SIGNIFICANCE: Continuous glucose monitoring system shows the dynamic of glucose concentration in ketogenic diet treatment initiation. It may be a useful tool to control the effects of this diet on glucose metabolism, especially in hypoglycemia detection.

Group comparisons of the individual electroretinogram time trajectories for the ascending limb of the b-wave using a raw and registered time series.

OBJECTIVES: The electroretinogram is a clinical test commonly used in the diagnosis of retinal disorders with the peak time and amplitude of the a- and b-waves used as the main indicators of retinal function. However, subtle changes that affect the shape of the electroretinogram waveform may occur in the early stages of disease or in conditions that have a neurodevelopmental or neurodegenerative origin. In such cases, we introduce a statistical approach to mathematically model the shape of the electroretinogram waveform that may aid clinicians and researchers using the electroretinogram or other biological signal recordings to identify morphological features in the waveforms that may not be captured by the time or time-frequency domains of the waveforms. We present a statistical graphics-based analysis of the ascending limb of the b-wave (AL-b) of the electroretinogram in children with and without a diagnosis of autism spectrum disorder (ASD) with a narrative explanation of the statistical approach to illustrate how different features of the waveform based on location and scale derived from raw and registered time series can reveal subtle differences between the groups. RESULTS: Analysis of the raw time trajectories confirmed findings of previous studies with a reduced and delayed b-wave amplitude in ASD. However, when the individual time trajectories were registered then group differences were visible in the mean amplitude at registered time ~ 0.6 suggesting a novel method to differentiate groups using registration of the ERG waveform.

Fish scale stable isotopes as potential indicators of nutrient pollution: Exploring the response of roach (Rutilus rutilus) scale δ15N and δ13C to a gradient of land use disturbance.

To examine the suitability of fish scales as potential tracers of nutrient pollution, we analysed the nitrogen and carbon stable isotope values (δ15N and δ13C) in scales of a generalist fish species, roach Rutilus rutilus, collected from 22 Czech reservoirs covering wide gradients of catchment land use and nutrient enrichment. Using generalised additive mixed models in the first step and generalised linear mixed models in the second step, we evaluated the response of roach scale stable isotope values to catchment land use variables (percentage of agricultural land and human population density) and in-reservoir water quality variables. Roach scale δ15N values varied by 15 ‰ among the reservoirs and were strongly, linearly, and positively associated with the percentage of agricultural land in the reservoir catchments, pointing to agriculture as the dominant source of nitrogen pollution in the investigated systems. Roach scale δ13C values differed by 8 ‰ among the studied reservoirs and were not related to catchment land use variables or in-reservoir primary production (chlorophyll-a levels). Possible variation in roach foraging strategies (littoral versus pelagic) between reservoirs or the contrasting effects of eutrophication-related autotrophic and heterotrophic processes on baseline δ13C values may explain the lack of relationships between roach scale δ13C values and the explanatory variables. In summary, our findings show that fish scale δ15N values are sensitive bioindicators of catchment-derived anthropogenic nitrogen inputs to freshwater ecosystems. Because scales can be sampled in a nonlethal way and δ15N analysis is relatively inexpensive, we suggest that measuring the δ15N values of fish scales could be an effective method for monitoring nitrogen pollution in aquatic environments.