Levels of per- and polyfluoroalkyl substances (PFAS) in Norwegian children stratified by age and sex - Data from the Bergen Growth Study 2.

BACKGROUND AND AIM: Due to the persistence, bioaccumulation and potential adverse health effects, there have been restrictions and phase out in the production of certain per- and polyfluoroalkyl substances (PFAS) since the early 2000s. Published serum levels of PFAS during childhood are variable and may reflect the impact of age, sex, sampling year and exposure history. Surveying the concentrations of PFAS in children is vital to provide information regarding exposure during this critical time of development. The aim of the current study was therefore to evaluate serum concentrations of PFAS in Norwegian schoolchildren according to age and sex. MATERIAL AND METHODS: Serum samples from 1094 children (645 girls and 449 boys) aged 6-16 years, attending schools in Bergen, Norway, were analyzed for 19 PFAS. The samples were collected in 2016 as part of the Bergen Growth Study 2. Statistical analyses included Student t-test, one-way ANOVA and Spearman's correlation analysis of log-transformed data. RESULTS: Of the 19 PFAS examined, 11 were detected in the serum samples. Perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS) and perfluorononaoic acid (PFNA) were present in all samples with geometric means of 2.67, 1.35, 0.47 and 0.68 ng/mL, respectively. In total, 203 children (19%) had PFAS levels above the safety limits set by the German Human Biomonitoring Commission. Significantly higher serum concentrations were found in boys compared to girls for PFOS, PFNA, PFHxS and perfluoroheptanesulfonic acid (PFHpS). Furthermore, serum concentrations of PFOS, PFOA, PFHxS and PFHpS were significantly higher in children under the age of 12 years than in older children. CONCLUSIONS: PFAS exposure was widespread in the sample population of Norwegian children analyzed in this study. Approximately one out of five children had PFAS levels above safety limits, indicating a potential risk of negative health effects. The majority of the analyzed PFAS showed higher levels in boys than in girls and decreased serum concentrations with age, which may be explained by changes related to growth and maturation.

Deep phenotyping of pubertal development in Norwegian children: the Bergen Growth Study 2.

BACKGROUND: The Bergen Growth Study 2 (BGS2) aims to characterise somatic and endocrine changes in healthy Norwegian children using a novel methodology. SUBJECTS AND METHODS: A cross-sectional sample of 1285 children aged 6-16 years was examined in 2016 using novel objective ultrasound assessments of breast developmental stages and testicular volume in addition to the traditional Tanner pubertal stages. Blood samples allowed for measurements of pubertal hormones, endocrine disruptive chemicals, and genetic analyses. RESULTS: Ultrasound staging of breast development in girls showed a high degree of agreement within and between observers, and ultrasound measurement of testicular volume in boys also showed small intra- and interobserver differences. The median age was 10.4 years for Tanner B2 (pubertal onset) and 12.7 years for menarche. Norwegian boys reached a pubertal testicular volume at a mean age of 11.7 years. Continuous reference curves for testicular volume and sex hormones were constructed using the LMS method. CONCLUSIONS: Ultrasound-based assessments of puberty provided novel references for breast developmental stages and enabled the measurement of testicular volume on a continuous scale. Endocrine z-scores allowed for an intuitive interpretation of changing hormonal levels during puberty on a quantitative scale, which, in turn, provides opportunities for further analysis of pubertal development using machine-learning approaches.

Reference Curves for Pediatric Endocrinology: Leveraging Biomarker Z-Scores for Clinical Classifications.

CONTEXT: Hormone reference intervals in pediatric endocrinology are traditionally partitioned by age and lack the framework for benchmarking individual blood test results as normalized z-scores and plotting sequential measurements onto a chart. Reference curve modeling is applicable to endocrine variables and represents a standardized method to account for variation with gender and age. OBJECTIVE: We aimed to establish gender-specific biomarker reference curves for clinical use and benchmark associations between hormones, pubertal phenotype, and body mass index (BMI). METHODS: Using cross-sectional population sample data from 2139 healthy Norwegian children and adolescents, we analyzed the pubertal status, ultrasound measures of glandular breast tissue (girls) and testicular volume (boys), BMI, and laboratory measurements of 17 clinical biomarkers modeled using the established "LMS" growth chart algorithm in R. RESULTS: Reference curves for puberty hormones and pertinent biomarkers were modeled to adjust for age and gender. Z-score equivalents of biomarker levels and anthropometric measurements were compiled in a comprehensive beta coefficient matrix for each gender. Excerpted from this analysis and independently of age, BMI was positively associated with female glandular breast volume (ß = 0.5, P < 0.001) and leptin (ß = 0.6, P < 0.001), and inversely correlated with serum levels of sex hormone-binding globulin (SHBG) (ß = -0.4, P < 0.001). Biomarker z-score profiles differed significantly between cohort subgroups stratified by puberty phenotype and BMI weight class. CONCLUSION: Biomarker reference curves and corresponding z-scores provide an intuitive framework for clinical implementation in pediatric endocrinology and facilitate the application of machine learning classification and covariate precision medicine for pediatric patients.

Psychological health in preschool children with underweight, overweight or obesity: a regional cohort study.

Objective: To examine if underweight (UW), overweight (OW) or obesity (OB), or body mass index (BMI) expressed as its SD score (BMI SDS), were associated with psychological difficulties in preschool children. Design: Regional cohort study. Setting: Oppland County, Norway. Methods: At the routine school entry health assessment at 5-6 years of age, parents were invited to participate by local public health nurses. The parents completed questionnaires on sociodemographic, health and lifestyle factors of the child and the family, and on the child's neurocognitive development. They assessed psychological health with the Strengths and Difficulties Questionnaire (SDQ). Public health nurses measured weight and height on all eligible children and reported age, sex, height and weight anonymously for the children who declined to participate. Participants: We obtained information on 1088 of 1895 (57%) eligible children. The proportion of UW, OW and OB was slightly higher among the children who declined. Main outcome measures: SDQ subscale and Total Difficulties Scores. Results: The mean SDQ scores and proportion of scores ≥the 90th percentile had a curvilinear pattern from UW through normal weight (NW), OW and OB with NW as nadir, but the pattern was only significant for the mean Emotional problems, Peer problems and Total SDQ Scales, and for the Total SDQ Score ≥the 90th percentile (TDS90). After adjusting for relevant social, developmental, health and behavioural characteristics, TDS90 was only significantly associated with UW in multiple logistic regression analyses, and only with the lowest quartile of BMI SDS in a linear spline regression analysis. Conclusions: The study suggests that UW and low BMI, but not OW, OB or higher BMI, are independent risk factors for having psychological symptoms in preschool children.

Low BMI, but not high BMI, influences the timing of puberty in boys.

BACKGROUND: Previous studies investigating the association between weight status and onset of puberty in boys have been equivocal. It is currently unclear to what extent weight class influences puberty onset and progression. OBJECTIVES: To explore the relationship between degree of sexual maturation and anthropometric measures in Norwegian boys. METHODS: The following endpoints were collected in a Norwegian cross-sectional study of 324 healthy boys aged 9-16: ultrasound-determined testicular volume (USTV), total serum testosterone, Tanner pubic hair stage, height, weight, waist circumference (WC), subscapular skinfolds (SSF), and body fat percentage (%BF). Testicular volume-for-age z-scores were used to classify "early," "average," or "late" maturing boys. Ordinal logistic regression analyses with a proportional odds model were applied to analyze the association between anthropometric variables and age-adjusted degree of pubertal development, with results expressed as age-adjusted odds ratios (AOR). Cumulative incidence curves for reaching pubertal milestones were stratified by BMI. RESULTS: Boys with a low BMI for age (BMIz  < -1) were less likely to have reached a pubertal testicular volume (USTV ≥ 2.7 mL) or a pubertal serum level of testosterone (≥0.5 nmol/L) compared to normal weight boys (AOR 0.3, p = 0.038, AOR 0.3, p = 0.026, respectively), and entered puberty on average with a delay of approximately eight months. Boys with high BMI for age (BMIz  > 1) exhibited a comparable timing as normal weight boys. The same was found for WC. Pubertal markers were not associated with SSF or %BF. CONCLUSION: By examining the association between puberty and weight status classified as low, average, or high, we found that a low BMI or WC for age were associated with a less advanced pubertal development and delayed timing of puberty in boys. No significant association was observed for a high BMI or WC. Moreover, no significant effects of SSF or %BF were observed. A low weight status should also be considered when assessing pubertal development in boys.

Hormone References for Ultrasound Breast Staging and Endocrine Profiling to Detect Female Onset of Puberty.

CONTEXT: Application of ultrasound (US) to evaluate attainment and morphology of glandular tissue provides a new rationale for evaluating onset and progression of female puberty, but currently no hormone references complement this method. Furthermore, previous studies have not explored the predictive value of endocrine profiling to determine female puberty onset. OBJECTIVE: To integrate US breast staging with hypothalamic-pituitary-gonadal hormone references and test the predictive value of an endocrine profile to determine thelarche. DESIGN SETTING AND PARTICIPANTS: Cross-sectional sample of 601 healthy Norwegian girls, ages 6 to 16 years. MAIN OUTCOME MEASURES: Clinical and ultrasound breast evaluations were performed for all included girls. Blood samples were analyzed by immunoassay and ultrasensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify estradiol (E2) and estrone (E1) from the subpicomolar range. RESULTS: References for E2, E1, luteinizing hormone, follicle-stimulating hormone, and sex hormone-binding globulin were constructed in relation to chronological age, Tanner stages, and US breast stages. An endocrine profile index score derived from principal component analysis of these analytes was a better marker of puberty onset than age or any individual hormone, with receiver-operating characteristic area under the curve 0.91 (P < 0.001). Ultrasound detection of nonpalpable glandular tissue in 14 out of 264 (5.3%) girls with clinically prepubertal presentation was associated with significantly higher median serum levels of E2 (12.5 vs 4.9 pmol/L; P < 0.05) and a distinct endocrine profile (arbitrary units; P < 0.001). CONCLUSIONS: We provide the first hormone references for use with US breast staging and demonstrate the application of endocrine profiling to improve detection of female puberty onset.

References for Ultrasound Staging of Breast Maturation, Tanner Breast Staging, Pubic Hair, and Menarche in Norwegian Girls.

CONTEXT: Discriminating adipose and glandular tissue is challenging when clinically assessing breast development. Ultrasound facilitates staging of pubertal breast maturation (US B), but has not been systematically compared to Tanner breast (Tanner B) staging, and no normative data have been reported. OBJECTIVE: To present normative references for US B along with references for Tanner B, pubic hair (PH), and menarche. DESIGN, SETTING, AND PARTICIPANTS: A cross-sectional sample of 703 healthy girls aged 6 to 16 years were examined. MAIN OUTCOME MEASURES: Breast development was determined with US B and Tanner B staging. Tanner PH and menarcheal status were recorded. The age distributions of entry in US B, Tanner B, and PH stages and menarche were estimated with generalized linear and generalized additive models with a probit link. Method agreement was tested with weighted Cohen's kappa. RESULTS: The median (±2SD) ages for thelarche, US B2 and Tanner B2, were 10.2 (7.7, 12.8) and 10.4 (8.0, 12.7) years. The median (±2SD) ages at Tanner PH2 and menarche were 10.9 (8.5, 13.3) and 12.7 (11.0, 16.2) years. Cohen's kappa of agreement (95% confidence interval) between US B and Tanner B was 0.87 (0.85-0.88). When the methods disagreed, US B was usually more advanced. CONCLUSION: Thelarche occurred at a slightly younger age when assessed with ultrasound compared to clinical Tanner staging, although the 2 methods had a very good agreement when determining pubertal breast maturation. A significant decrease of 2.8 months in age at menarche was observed during the past decade in Norwegian girls.

Reference data for testicular volume measured with ultrasound and pubic hair in Norwegian boys are comparable with Northern European populations.

AIM: To estimate references for testicular volume measured with ultrasound and Tanner stages of pubic hair in Norwegian boys, and to compare the timing of puberty with data from similar populations. METHODS: Testicular volume was derived from ultrasound measurements of testicular volume in a cross-sectional study of 514 healthy boys. A continuous testicular volume for age reference curve was estimated with the LMS method. Tanner stages for pubic hair were clinically assessed in 452 boys. Age references for pubertal milestones were estimated with probit regression. RESULTS: Puberty onset, defined by an ultrasound testicular volume of 2.7 mL, equivalent to an orchidometer volume of 4 mL, occurred at a mean (SD) age of 11.7 (1.1) years. The reference range was 9.7 (3rd) to 13.7 years (97th percentile). Pubic hair (Tanner stage 2) appeared on average at 11.8 (1.2) years with a corresponding reference range of 9.5-14.1 years. CONCLUSION: The references for testicular volume measured with ultrasound are continuous in age and allow for the quantification of pubertal development. The age distribution of reaching pubertal milestones was comparable with data from other Northern European countries.

A family-oriented intervention programme to curtail obesity from five years of age had no effect over no intervention.

AIM: To examine the effect of a family-oriented multidisciplinary intervention programme to curtail weight increase in young children with obesity. METHODS: Children who weighed more than one kilogram above the 97th percentile for height at the preschool assessment in Oppland County, Norway, were identified. Parents residing in one part of the county were invited to participate in a group-based three-year intervention programme while the rest had no interventions. Body mass index (BMI) and family characteristics at entry and measurements at birth were explanatory variables, and change in BMI standard deviation score (SDS) the outcome measure. For the intervention group, outcome was also related to skinfold thicknesses, waist-to-height ratio and physical ability. RESULTS: The programme was completed by 31 families in the intervention and 33 in the control group. At entry, the respective median (interquartile) age was 5.83 (0.36) and 5.74 (0.66) years, and the BMI SDS 2.35 (1.06) and 1.95 (0.49), P = .012. The median decrease in BMI SDS was 0.19 in both groups. The decline increased with increasing BMI SDS at entry, but irrespective of group. Social or behavioural factor or other anthropometric measures were not associated with outcome. CONCLUSION: The intervention programme had no effect on BMI SDS.

Norwegian children and adolescents in blended families are at risk of larger one-year BMI increments.

AIM: To study how sociodemographic factors and family structure associate with baseline BMI z-scores (BMIz) and BMIz change in 767 Norwegian children aged 6-15 years. METHODS: Baseline BMIz and 1-year BMIz increments in children from the Bergen Growth Study were analysed with linear and logistic regression, according to sociodemographic factors and family structure. A blended family was defined as including a step-parent and/or half-sibling. RESULTS: In a fully adjusted regression model, baseline BMIz were only significantly associated with maternal BMI (b = 0.087, 95%CI 0.067, 0.107). Body Mass Index z-scores increments were larger in children living in a blended family (b = 0.060, 95%CI 0.006, 0.115), with a lower parental education (b = 0.127, 95%CI 0.029, 0.226) and with a higher maternal BMI (b = 0.008, 95%CI 0.001, 0.014). The odds for a large BMIz increment (>1 SD) were higher in children living in blended families (OR 1.82, 95%CI 1.16, 2.88) and with higher maternal BMI (OR 1.07, 95%CI 1.01, 1.13) and lower in 9-11-year-old children (OR 0.44, 95%CI 0.26, 0.77) compared with 12-15-year-olds. CONCLUSION: Body Mass Index z-scores increments were more strongly associated with sociodemographic factors and living in a blended family than baseline BMIz values. BMI z-scores increments could be useful for identifying children at risk of becoming overweight or obese.

Testicular Ultrasound to Stratify Hormone References in a Cross-Sectional Norwegian Study of Male Puberty.

CONTEXT: Testicular growth represents the best clinical variable to evaluate male puberty, but current pediatric hormone references are based on chronological age and subjective assessments of discrete puberty development stages. Determination of testicular volume (TV) by ultrasound provides a novel approach to assess puberty progression and stratify hormone reference intervals. OBJECTIVE: The objective of this article is to establish references for serum testosterone and key hormones of the male pituitary-gonadal signaling pathway in relation to TV determined by ultrasound. DESIGN, SETTING, AND PARTICIPANTS: Blood samples from 414 healthy Norwegian boys between ages 6 and 16 years were included from the cross-sectional "Bergen Growth Study 2." Participants underwent testicular ultrasound and clinical assessments, and serum samples were analyzed by liquid chromatography tandem-mass spectrometry and immunoassays. MAIN OUTCOME MEASURES: We present references for circulating levels of total testosterone, luteinizing hormone, follicle-stimulating hormone, and sex hormone-binding globulin in relation to TV, chronological age, and Tanner pubic hair stages. RESULTS: In pubertal boys, TV accounted for more variance in serum testosterone levels than chronological age (Spearman r = 0.753, P < .001 vs r = 0.692, P < .001, respectively). Continuous centile references demonstrate the association between TV and hormone levels during puberty. Hormone reference intervals were stratified by TV during the pubertal transition. CONCLUSIONS: Objective ultrasound assessments of TV and stratification of hormone references increase the diagnostic value of traditional references based on chronological age or subjective staging of male puberty.

Associations between different weight-related anthropometric traits and lifestyle factors in Norwegian children and adolescents: A case for measuring skinfolds.

OBJECTIVES: The purpose of this study was to investigate the association between weight-related anthropometric measures and children's eating habits, physical activity and sedentary lifestyle at a population level. METHODS: Data from the Bergen Growth Study were used to study the association of z-scores of waist circumference (WC), weight-to-height ratio (WHtR), subscapularis (SSF) and triceps (TSF) skinfolds and BMI, with lifestyle factors in 3063 Norwegian children (1543 boys) aged 4-15 years, using linear regression analysis. Each sex was analyzed separately. RESULTS: In a fully adjusted model with additional correction for BMI z-scores, the consumption of vegetables was associated with higher WC (b = 0.03) and TSF (b = 0.05) z-scores in girls. Sedentary behavior was not associated with any of the anthropometric measures. Physical activity was negatively associated with SSF (b = -0.07) and TSF (b = -0.07) z-scores in boys, while a significant negative association was observed with WC (b = -0.02), WHtR (b = -0.03), SSF (b = -0.04) and TSF (b = -0.06) in girls. CONCLUSION: Physical activity was negatively associated with skinfolds in both sexes. The BMI was not related to the level of physical activity, and should be complemented with direct measures of fat tissue, like skinfolds, when studying the effect of physical activity on body composition in children.

Ultrasound-based measurements of testicular volume in 6- to 16-year-old boys - intra- and interobserver agreement and comparison with Prader orchidometry.

BACKGROUND: Prader orchidometry has been the standard method for evaluating testicular size. As this technique is subjective and tends to overestimate the testicular volume, ultrasound (US) has been proposed as more reliable. OBJECTIVE: To evaluate the intra- and interobserver agreement of US measurements of testicular volume and to compare US with the Prader orchidometer. MATERIALS AND METHODS: Dimensions of the right testicle were measured using US in 57 boys ages 6.5 to 16.4 years (mean: 12.0 years). The measurements were performed twice by one main observer and once by a second observer. A third observer estimated testicular volume using a Prader orchidometer. Agreement was investigated with Bland-Altman plots, summarized as the mean and standard deviation (SD) of differences, 95% limits of agreement and technical error of measurement. RESULTS: Mean intra-observer difference of testicular volume was 2.2%, SD=9.2% (limits of agreement: -20.3 to 15.9%) and technical error of measurement 6.5%. The mean interobserver difference was 4.8%, SD=20.7% (limits of agreement: -35.7 to 45.3%) and technical error of measurement 14.6%. Comparing US and orchidometer volumes required conversion that was nonlinear and volume dependent, estimated as VolOM = 1.96×VolUS0.71. The mean difference after transformation was 0.7% with an SD of 18.0% (limits of agreement: -34.5 to 35.9%). CONCLUSION: Our results showed a small mean intra- and interobserver difference that indicates the potential of US for measurement of testicular volume at group level. The intra-observer error was limited, which justifies its use in longitudinal follow-up of testicular development in an individual child, but the larger interobserver variability indicates the need for good standardization of methods. Agreement between the two methods requires a power transformation.

Ultrasound assessment of pubertal breast development in girls: intra- and interobserver agreement.

BACKGROUND: Clinical assessment of pubertal breast development using Tanner staging is subjective. This has led to the introduction of ultrasound (US), aiming for a more objective analysis. However, information regarding its reliability is lacking. OBJECTIVE: To examine intra- and interobserver agreement of breast maturity staging using US and to examine the precision of direct measurements of the gland. MATERIALS AND METHODS: Fifty-seven healthy girls (mean age: 10.9 years, range: 6.1 to 15.9 years) were examined independently by two observers using US of the left breast to score the glandular maturity stage on a 0-5 scale, and to measure the depth and diameter. One observer repeated the examination after 20 to 35 min to assess intra-observer agreement. Cohen's kappa with linear weights was used to examine intra- and interobserver agreement of the US staging, while the measurement precision was analyzed using Bland-Altman plots and 95% limits of agreement. RESULTS: The agreement of US staging on a 0-5 scale was very good (kappa 0.84; 95% confidence interval [CI] 0.78-0.91) for intra-observer observation and good (kappa 0.71; 95% CI 0.62-0.80) for interobserver observation. Measurements of glandular depth and diameter were unbiased for a single observer, but the variances were large both within and between observers. CONCLUSION: US using a scale from 0 to 5 is a reliable method to stage the development of glandular breast tissue during puberty in healthy girls. Measurements of glandular depth and diameter were found to be imprecise.

Social and somatic determinants of underweight, overweight and obesity at 5 years of age: a Norwegian regional cohort study.

OBJECTIVE: To identify associations between the weight groups underweight (UW), overweight (OW) and obesity (OB) at 5 years of age and exposures related to pregnancy, anthropometric measures at birth, sociodemographic factors, and family health, anthropometric measures and habits. DESIGN: Regional cohort study. SETTING: Oppland County, Norway. METHODS: Pregnancy data were obtained from a prospective perinatal register for children born in the county, and weight and height were measured by midwives at birth and by public health nurses at 5 years. Other information was obtained from questionnaires completed by parents. PARTICIPANTS: Of 1895 eligible children, current weight and height were obtained for all, weight and length at birth and information from parents for 1119 (59%) and pregnancy register data for 749 (40%) of the children. The significance of potential explanatory variables from descriptive statistics was tested in multinomial logistic regression analysis. RESULTS: The prevalence of UW, OW and OB among participants was 7.8%, 10.6% and 3.5%, respectively. UW was associated with anthropometric measures at birth and those of parents, but not with sociodemographic or behavioural characteristics. OW and OB were associated with anthropometric measures of parents and siblings and with a variety of unfavourable social characteristics, lack of prolonged breast feeding, sedentary behaviour and dental caries, but not with current dietary habits. After adjustments, OW and OB were marginally related to birth parameters and diet and unrelated to physical activity, but significantly related to parental body mass index, low parental education and maternal smoking. CONCLUSION: The strong associations between sociodemographic and behavioural factors and OW and OB, but not with UW, may suggest that environmental factors are major contributing causes of OW and particularly OB at 5 years. These results may be helpful in targeting preventive measures against OW and OB.

Timing of menarche in Norwegian girls: associations with body mass index, waist circumference and skinfold thickness.

BACKGROUND: Research studies show conflicting results regarding the association between menarche and body weight. The purpose of the present study was to investigate if anthropometric indicators of body composition, body mass index (BMI), waist circumference (WC), triceps (TSF) and subscapular skinfold (SSF) thicknesses, were differentially associated with age at menarche in Norwegian girls. METHODS: The association between menarche and BMI, WC, TSF and SSF was investigated in 1481 girls aged 8-15.5 years, and in a subgroup of 181 girls with menarche during the 12 months prior to examination. Anthropometric measures were categorized as low (< -1SDS), average (-1 ≤ SDS ≤ +1) or high (> 1SDS), and menarche according to this classification was analysed with Kaplan-Meier curves and unadjusted and adjusted Cox regression. RESULTS: The median age at menarche in the total sample was 13.1 years. In the unadjusted models, low categories of all traits were associated with later menarche, and high categories with earlier menarche. When adjusted for other covariates, earlier menarche was only related with a high BMI (Hazard Ratio 1.41, 95% confidence interval (CI) 1.07, 1.85), and later menarche with a low BMI (HR 0.53, 95%CI 0.38, 0.75) and low SSF (HR 0.54, 95%CI 0.39, 0.75). In girls with recent menarche, early menarche was significantly associated with a high BMI in the final model (HR 1.79, 95%CI 1.23, 2.62). CONCLUSIONS: The timing of menarche was associated with the BMI, WC, TSF and SSF, but more strongly so with the BMI. These associations may be related to a common tempo of growth, as the mean age at menarche has remained stable during the last decades during a time period while the prevalence of overweight and obesity has increased significantly.

BMI and BMI SDS in childhood: annual increments and conditional change.

Background Early detection of abnormal weight gain in childhood may be important for preventive purposes. It is still debated which annual changes in BMI should warrant attention. Aim To analyse 1-year increments of Body Mass Index (BMI) and standardised BMI (BMI SDS) in childhood and explore conditional change in BMI SDS as an alternative method to evaluate 1-year changes in BMI. Subjects and methods The distributions of 1-year increments of BMI (kg/m2) and BMI SDS are summarised by percentiles. Differences according to sex, age, height, weight, initial BMI and weight status on the BMI and BMI SDS increments were assessed with multiple linear regression. Conditional change in BMI SDS was based on the correlation between annual BMI measurements converted to SDS. Results BMI increments depended significantly on sex, height, weight and initial BMI. Changes in BMI SDS depended significantly only on the initial BMI SDS. The distribution of conditional change in BMI SDS using a two-correlation model was close to normal (mean = 0.11, SD = 1.02, n = 1167), with 3.2% (2.3-4.4%) of the observations below -2 SD and 2.8% (2.0-4.0%) above +2 SD. Conclusion Conditional change in BMI SDS can be used to detect unexpected large changes in BMI SDS. Although this method requires the use of a computer, it may be clinically useful to detect aberrant weight development.