Neck circumference percentile: A screening tool for pediatric obstructive sleep apnea

Obstructive Sleep Apnea in Pediatrics and Adolescent Women: A Systematic Review of Sex-Based Differences Between Girls and Boys

BACKGROUND/OBJECTIVES

Obstructive sleep apnea (OSA) is marked by repetitive occurrences of upper airway (UA) obstruction during sleep. Morbidities impacting the metabolic, cardiovascular (CV) and neurological systems are correlated with OSA. Only a few studies have described the existence of different characteristics depending on sex and, to date, the girl phenotype in OSA pediatrics is not well known. The objective of this systematic review is to identify the specific phenotype of OSA in pediatric and adolescent females compared to males.

METHODS

A systematic review was performed. The terms "pediatric sleep apnea" and "sex differences" were used to look for publications using PubMed, the Cochrane Library and Web of Science.

INCLUSION CRITERIA

(1) peer-reviewed journal articles written in English; (2) investigations conducted on individuals diagnosed with OSA; and (3) investigations providing information about sex differences.

EXCLUSION CRITERIA

(1) studies carried out with individuals aged 18 years and older; (2) studies involving a sample size of fewer than 10 patients; and (3) editorials, letters and case reports.

RESULTS

Fifteen studies were included and classified in sections related to sex-based differences.

CONCLUSIONS

Limited information related to sex-based OSA differences in the pediatric population exists. These differences are conditioned by hormonal status, and are minimal in the premenarcheal period. Moreover, adolescent women present a lower prevalence of obesity and craniofacial alterations, lower OSA severity related to higher UA area and earlier tonsil regression. Hyperactivity is more frequent in boys. Some studies pointed to a higher risk of high diastolic blood pressure in girls than in boys.

Estimating the severity of obstructive sleep apnea during wakefulness using speech: A review

Obstructive sleep apnea (OSA) is a chronic breathing disorder during sleep that affects 10-30% of adults in North America. The gold standard for diagnosing OSA is polysomnography (PSG). However, PSG has several drawbacks, for example, it is a cumbersome and expensive procedure, which can be quite inconvenient for patients. Additionally, patients often have to endure long waitlists before they can undergo PSG. As a result, other alternatives for screening OSA have gained attention. Speech, as an accessible modality, is generated by variations in the pharyngeal airway, vocal tract, and soft tissues in the pharynx, which shares similar anatomical structures that contribute to OSA. Consequently, in this study, we aim to provide a comprehensive review of the existing research on the use of speech for estimating the severity of OSA. In this regard, a total of 851 papers were initially identified from the PubMed database using a specified set of keywords defined by population, intervention, comparison and outcome (PICO) criteria, along with a concatenated graph of the 5 most cited papers in the field extracted from ConnectedPapers platform. Following a rigorous filtering process that considered the preferred reporting items for systematic reviews and meta-analyses (PRISMA) approach, 32 papers were ultimately included in this review. Among these, 28 papers primarily focused on developing methodology, while the remaining 4 papers delved into the clinical perspective of the association between OSA and speech. In the next step, we investigate the physiological similarities between OSA and speech. Subsequently, we highlight the features extracted from speech, the employed feature selection techniques, and the details of the developed models to predict OSA severity. By thoroughly discussing the current findings and limitations of studies in the field, we provide valuable insights into the gaps that need to be addressed in future research directions.

Anthropometric measures and obstructive sleep apnea in children and adolescents: a systematic review of the literature and meta-analysis

BACKGROUND

Anthropometric measurements can be used to identify children at risk of developing obstructive sleep apnea (OSA). The study aimed to assess which anthropometric measurements (AMs) are most associated with an increased predisposition to develop OSA in healthy children and adolescents.

METHODS

We performed a systematic review (PROSPERO #CRD42022310572) that searched eight databases and gray literature.

RESULTS

In eight studies with low-to-high risk of bias, investigators reported the following AMs: body mass index (BMI), neck circumference, hip circumference, waist-to-hip ratio, neck-to-waist ratio, waist circumference, waist-to-height ratio, and facial AMs. The meta-analysis showed that the OSA group had an average of 1.00 cm greater for the neck circumference (p < 0.001; Cohen's d = 2.26 [0.72, 5.23]), 3.07 cm greater for the waist circumference (p = 0.030; Cohen's d = 0.28 [0.02, 0.53]), 3.96 cm greater for the hip circumference (p = 0.040; Cohen's d = 0.28 [0.02, 0.55]), 5.21° greater for the cervicomental angle (p = 0.020; Cohen's d = 0.31 [0.03, 0.59]), and 1.23° greater for maxillary-mandibular relationship angle (p < 0.001; Cohen's d = 0.47 [0.22, 0.72]) than the control group. The mandibular depth angle had a reduction of 1.86° (p = 0.001; Cohen's d = -0.36° [-0.65, -0.08]) in control than in patients with OSA. The BMI (p = 0.180), waist-to-hip ratio (p = 0.280), neck-to-waist ratio (p = 0.070), maxillary depth angle (p = 0.250), and upper/lower face height ratio (p = 0.070) showed no significant differences between groups.

CONCLUSIONS

Compared to the control group, the OSA group exhibited a greater mean difference in neck circumference, the only anthropometric measurement with high certainty of evidence.

Is adenotonsillectomy effective in improving central apnea events in patients with obstructive sleep apnea? A systematic review and meta-analysis

PURPOSE

To evaluate the effects of adenotonsillectomy on improving central sleep apnea events in children with obstructive sleep apnea (OSA).

METHODS

We searched four online databases for relevant articles published from inception until October 2022. We included studies that measured the number of central apnea events per sleep and central apnea-hypopnea index (CAHI) or central apnea index (CAI) scores in children with OSA before and after adenotonsillectomy. Our primary outcomes were changes in CAI scores, the number of central apnea events per sleep, and CAHI scores after surgery. Our secondary outcomes were changes in total and mixed apnea events, improvement of sleep outcomes, and differences in oxygen or carbon dioxide saturation during sleep. We performed meta-analyses by pooling the mean changes of all included studies with a 95% confidence interval using Stata 17. Subsequently, we performed subgroup analyses based on the presence of comorbidities.

RESULTS

We included 22 studies comprising 1287 patients. Central and total sleep apnea parameters, except for CAHI and mixed apnea index scores, showed significant improvements after surgery. In addition, all respiratory parameters and second and third stages of non-rapid eye movement sleep showed significant postsurgical improvements. Patients with comorbidities showed significant improvements only in the total apnea-hypopnea index, oxygen desaturation index, and minimal oxygen saturation.

CONCLUSION

Adenotonsillectomy improves central apnea events in patients with OSA but not in those with comorbidities.

Neck fat and obstructive sleep apnea in obese adolescents

STUDY OBJECTIVES

Increased neck circumference, a surrogate for the neck fat that can narrow the upper airway in obese individuals, is a risk factor for obstructive sleep apnea syndrome (OSAS) in adults, but the association between neck fat and OSAS in adolescent males and females is unknown. We hypothesized that obese adolescents with OSAS have more neck fat than controls, females more neck fat than males, and that neck fat correlates with obesity and OSAS severity.

METHODS

Obese adolescents with OSAS and obese and normal-weight controls underwent upper airway magnetic resonance imaging, polysomnography, and anthropometrics, including neck circumference measurement. Intra-neck and subcutaneous neck fat measurements were manually segmented and compared among the three groups using ANOVA and between males and females using t-tests. The relationship between polysomnographic parameters and neck fat measurements was assessed in adolescents with OSAS using Pearson correlations.

RESULTS

One-hundred nineteen adolescents (38 females) were studied: 39 obese with OSAS, 34 obese controls, and 46 normal-weight controls. Neck fat was not greater in adolescents with OSAS compared to obese controls (p=0.35), and neck fat volume was not related to OSAS severity (p = 0.36). However, obese adolescents had more neck fat than normal-weight controls (p < 0.001), and neck fat volume correlated with neck circumference (r = 0.53, p < 0.001). Females had significantly greater cross-sectional neck fat than males (p < 0.001).

CONCLUSIONS

While neck fat is associated with obesity and neck circumference in adolescents and is greater in females versus males, it does not appear to correlate with presence and severity of OSAS.

Developing neck circumference growth reference charts for Pakistani children and adolescents using the lambda-mu-sigma and quantile regression method

OBJECTIVE

Neck circumference (NC) is currently used as an embryonic marker of obesity and its associated risks. But its use in clinical evaluations and other epidemiological purposes requires sex and age-specific standardised cut-offs which are still scarce for the Pakistani paediatric population. We therefore developed sex and age-specific growth reference charts for NC for Pakistani children and adolescents aged 2-18 years.

DESIGN

Cross-sectional multi-ethnic anthropometric survey (MEAS) study.

SETTING

Multan, Lahore, Rawalpindi and Islamabad.

PARTICIPANTS

The dataset of 10 668 healthy Pakistani children and adolescents aged 2-18 years collected in MEAS were used. Information related to age, sex and NC were taken as study variables. The lambda-mu-sigma (LMS) and quantile regression (QR) methods were applied to develop growth reference charts for NC.

RESULTS

The 5th, 10th, 25th, 50th, 75th, 90th and 95th smoothed percentile values of NC were presented. The centile values showed that neck size increased with age in both boys and girls. During 8 and 14 years of age, girls were found to have larger NC than boys. A comparison of NC median (50th) percentile values with references from Iranian and Turkish populations reveals substantially lower NC percentiles in Pakistani children and adolescents compared to their peers in the reference population.

CONCLUSION

The comparative results suggest that the uses of NC references of developed countries are inadequate for Pakistani children. A small variability between empirical centiles and centiles obtained by QR procedure recommends that growth charts should be constructed by QR as an alternative method.

Neck circumference cut-offs for overweight and obesity in a group of Mexican adolescents

BACKGROUND/OBJECTIVES

Neck circumference (NC) has been used for screening overweight/obesity for its high correlation with age, weight, body mass index (BMI), and waist circumference (WC). Cut-offs should be population specific. The aim of the study was to obtain cut-offs of NC for overweight/obesity in Mexican adolescents and to correlate them with anthropometric indicators.

SUBJECTS/METHODS

Weight, height, BMI, NC, WC, and mid-upper arm circumference (MUAC) of 465 12-14-year-old Mexican-mestizo students attending a public school in Mexico City were assessed. Using receiver operating characteristics analyses, neck cut-offs were obtained according to the WHO age and sex criteria for overweight/obesity.

RESULTS

NC cut-offs with the highest sensitivity and specificity for males and females, respectively, were as follows: 30.0 and 29.3 cm for 12-year-olds; 31.9 and 30.4 cm for 13-year-olds; and, 33.5 and 30.7 cm for 14-year-old adolescents. Overweight/obesity was identified with NC cut-offs in 80% of males and 86% of females, and showed significant correlations (p < 0.01) in males and females with weight (r = 0.821 and r = 0.840, respectively), BMI (r = 0.649 and r = 0.819, respectively), WC (r = 0.710 and r = 0.813, respectively) and MUAC (r = 0.736 and r = 0.815, respectively).

CONCLUSIONS

Neck circumference may be used as a first-stage screening tool or jointly with BMI to identify overweight/obesity in 12-14-year-old Mexican adolescents.

Does neck circumference predict obstructive sleep apnea in children with obesity?

OBJECTIVES

Obstructive sleep apnea (OSA) affects 10-50% of children with obesity, but its identification is challenging and wait times for testing are long. Previous studies suggest that neck circumference (NC) and neck-to-height ratio (NHR) may predict OSA. Our objectives were to 1) evaluate associations of NC and NHR with OSA; 2) model NHR as a predictor of OSA, adjusting for age, sex, and Tanner stage; and 3) identify thresholds of NHR associated with OSA, in children with obesity.

METHODS

Participants were aged 8-17 years, with obesity (BMI >95%ile), undergoing polysomnography. Associations between NC and NHR with OSA were evaluated. NHR, age, sex and self-reported Tanner stage (early/late) were included in a negative binomial multiple regression model to predict obstructive apnea hypopnea index (OAHI).

RESULTS

71 children participated, with median age 14.8 years (IQR 12.6, 16.0), 54% male, median BMI z-score 2.5 (IQR 2.3, 2.7), and 77% late Tanner stage. OSA was severe in 18 children (25.4%), moderate in 12 (16.9%), and mild in 18 (25.4%). In the model, each 0.01 increase in NHR was associated with a 55% increase in OAHI (95% CI: 36%, 80%); boys had a 119% higher OAHI than girls (95% CI: 10%, 337%). Threshold NHR associated with moderate-severe OSA was 0.25 in females and 0.23 in males.

CONCLUSIONS

NHR and male sex independently predict OSA severity in children with obesity, adjusting for age and Tanner stage. Children with obesity and NHR above identified thresholds are more likely to have moderate-severe OSA, and may benefit from earlier polysomnography.

Central sleep apnea in children with obstructive sleep apnea syndrome and improvement following adenotonsillectomy

BACKGROUND

Although the pathogenesis of central and obstructive events seems to be different, these two entities may somehow be related. We aimed to determine whether, as reported in previous research, the number of central sleep apnea (CSA) cases in a population of children with obstructive sleep apnea syndrome (OSAS) was greater than in patients without obstructive events, and if CSA worsens with increasing OSAS severity. As a second objective, we analyzed changes in central apnea index (CAI) after adenotonsillar surgery compared to changes when no surgery has been performed.

METHODS

We retrospectively reviewed nocturnal polysomnography (PSG) data from children between 1 and 14 years of age with no neurological conditions or syndromes. Patients with CAI values greater than 5 per hour were diagnosed as having CSA. Improvements of greater than 50% in CAI on repeat PSG were considered to represent a real change.

RESULTS

Data were available from 1279 PSG studies, resulting in 72 children with a CAI greater than 5 per hour (5.6%). Patients with OSAS showed a higher CAI (2.16) compared with those without OSAS (1.17), and this correlation increased with higher degrees of obstructive apnea severity. When adenotonsillectomy was performed due to OSAS, the CAI decreased by 1.37. The average decrease in PSG values was only 0.38 in cases where no surgery was performed.

CONCLUSION

The results of this study suggest that although CSA is perceived to be mostly associated with central nervous system ventilatory control, there may be a connection with airway obstruction and in children with CSA and OSA diagnosis adenotonsillectomy may improve both conditions.

Assessment and treatment of pediatric obstructive sleep apnea in Canada: history and current state of affairs

AIM

To highlight Canada's contributions to the assessment and treatment of pediatric obstructive sleep apnea as well as outline the current state of pediatric obstructive sleep apnea in Canada.

METHODS

A search was conducted in MEDLINE (Ovid) using Medical Subject Headings (MeSH) and free-text terms for 'child' and 'obstructive sleep apnea' with subsequent 'human' limit. The results were reviewed to identify publications where any author's listed a Canadian institution.

RESULTS

Canadian contributions to the field of pediatric obstructive sleep apnea have grown over the last 30 years with an increase in number of contributors and centres. Much of the early work stemmed from McGill University with important contributions in examining alternatives to polysomnography and post-adenotonsillectomy respiratory compromise. Today, contributors from centres across the country are engaged in the field and come from a greater diversity of disciplines. With continued challenges and opportunities, Canada will continue to help advance the field of pediatric OSA.

CONCLUSION

Canada has a strong community of people invested in continuing to work to improve the lives of Canadian children with pediatric OSA.

Utility of Neck, Height, and Tonsillar Size to Screen for Obstructive Sleep Apnea among Obese Youth

Objectives

To determine whether neck:height ratio combined with adenoid and tonsillar size is a good predictive tool for obstructive sleep apnea in obese youth.

Study Design

Cross-sectional study.

Setting

Sleep clinics at the Hospital for Sick Children, Toronto, Canada.

Subjects and Methods

Consented obese individuals aged 8 to 18 years were recruited between 2013 and 2015. Anthropometric measures were obtained by a trained research coordinator in a standardized manner. Otolaryngologists evaluated adenoid and tonsil sizes. Obstructive sleep apnea was diagnosed with an overnight polysomnogram as an obstructive apnea-hypopnea index ≥2. Multivariable logistic regressions investigated the relationship between potential predictors and obstructive sleep apnea. The C-statistic measured the predictive ability.

Results

Of the 53 subjects (median age, 13 years; 55% males), 28 (53%) were diagnosed with obstructive sleep apnea, with a median index of 10.6 per hour. In a logistic regression controlling for adenoid size, enlarged tonsils were significantly associated with the presence of obstructive sleep apnea ( P < .01). Adding neck:height ratio into the model improved the model predictive ability (C-index increased from 0.73 to 0.84). Controlling for tonsil and adenoid sizes, an increase in neck:height ratio was significantly associated with the presence of obstructive sleep apnea ( P = .01).

Conclusion

Our study suggests that neck:height ratio combined with tonsillar hypertrophy may have a strong predictive ability for obstructive sleep apnea and may be useful in an ambulatory setting to screen obese youth at high risk. These findings should be confirmed in a larger study.

Pediatric Pulmonology year in review 2015: Part 2

Pediatric Pulmonology covers a broad range of research and scholarly topics related to children's respiratory disorders. For updated perspectives on the rapidly expanding knowledge in our field, we will summarize the past year's publications in our major topic areas, as well as selected publications in these areas from the core clinical journal literature outside our own pages. The current review (Part 2) covers articles on sleep-disordered breathing. Pediatr Pulmonol. 2016;51:740-746. © 2016 Wiley Periodicals, Inc.

Modified STOP-Bang Tool for Stratifying Obstructive Sleep Apnea Risk in Adolescent Children

PURPOSE

Obstructive sleep apnea (OSA) is prevalent in children and diagnostic polysomnography is costly and not readily available in all areas. We developed a pediatric modification of a commonly used adult clinical prediction tool for stratifying the risk of OSA and the need for polysomnography.

METHODS

A total of 312 children (age 9-17 years) from phase 2 of the Tucson Children's Assessment of Sleep Apnea cohort study, with complete anthropomorphic data, parent questionnaires, and home polysomnograms were included. An adolescent modification of STOP-Bang (teen STOP-Bang) was developed and included snoring, tired, observed apnea, blood pressure ≥ 95th percentile, BMI > 95th percentile, academic problems, neck circumference >95th percentile for age, and male gender. An apnea-hypopnea index ≥ 1.5 events/hour was considered diagnostic of OSA.

RESULTS

Receiver Operator Characteristic (ROC) curves for parent-reported STOP-Bang scores were generated for teenage and pre-teen children. A STOP-Bang score of < 3 in teenagers was associated with a negative predictive value of 0.96. ROC curves were also generated based upon child-reported sexual maturity rating (SMR; n = 291). The ability of teen STOP-Bang to discriminate the presence or absence of OSA as measured by the AUC for children with SMR ≥ 4 (0.83; 95%CI 0.71-0.95) was better than children with SMR < 4 (0.63; 95%CI 0.46-0.81; p = 0.048).

CONCLUSIONS

In community dwelling adolescents, teen STOP-Bang may be useful in stratifying the risk of OSA.

[Detection and treatment of respiratory disorders in obese children: Obstructive sleep apnea syndrome and obesity hypoventilation syndrome]

Pediatric obesity may induce multiple complications, including cardiovascular and metabolic problems in adulthood. It may also cause respiratory disorders, which are not usually the first-intention diagnosis by physicians. The aim of this study was to evaluate how investigations had been performed in obese children referred to Timone Pediatric Hospital.

PATIENTS AND METHODS

A retrospective study of children referred to our department for severe non-syndromic obesity was conducted. The clinical features comprised history, anthropometric parameters, dietary habits, acanthosis nigricans, symptoms of obstructive sleep apnea syndrome (OSAS) as well as the paraclinical endocrine markers, blood gases, and sleep recordings.

RESULTS

Of 102 patients (mean age, 10.5±3.3 years; BMI Z-score, 4.52±1.5), 29.4% had OSAS symptoms (n=30). Nine had a pathological polysomnography confirming OSAS. Eight of them required ventilation: these children were the most severe with an earlier weight gain (2.17±1.2 years vs. 4.0±2.2 years; P=0.01) and a higher BMI Z-score (7.2±2.3 vs. 4.3±1.1; P=0.027). Obesity hypoventilation syndrome (OHS) was diagnosed in 3.9% of these children (n=4).

CONCLUSION

Diagnosis of OSAS and OHS, often overlooked in obese children, requires a systematic approach and early clinical detection of respiratory disorders. Better accessibility to sleep respiratory explorations would improve quality of care for these children.

Measurement of neck circumference and its correlation with body composition in a sample of students in São Paulo, Brazil

PURPOSE

The purpose of this study was to verify the correlation between neck circumference (NC) and body mass index (BMI) in children, and to determine NC percentiles for Brazilian children.

METHODS

The subjects of this cross-sectional study were students between the ages of 6 and 19 years from five schools in São Paulo, Brazil. Clinical and anthropometric data were collected from the students from April 2011 to June 2012. NC was measured at the level of the cricoid cartilage. We calculated Pearson correlation coefficients between NC and other indices of obesity with Sigma Stat 3.5. NC percentiles were produced using the LMS (lambda, mu, and sigma) method (STATA 12.0).

RESULTS

Among 2,794 students, 49.9% were male. NC was significantly correlated with age, BMI, waist circumference (WC), and body fat percentage (%BF). The NC of boys was greater than that of girls. The NC curves of smoothed 3rd, 10th, 25th, 50th, 75th, 90th, and 97th percentiles were constructed by age and sex.

CONCLUSIONS

NC can be used in the assessment of obesity in childhood. There was a positive correlation between NC and BMI, WC and %BF. This study was the first to provide NC percentiles for children in Brazil.

Caregivers' hair cortisol: a possible biomarker of chronic stress is associated with obesity measures among children with disabilities

BACKGROUND

The stress of caring for a loved one with chronic illness has been associated with childhood obesity. Hair cortisol has been proposed as a novel biomarker of chronic psychological stress. This study aimed to evaluate the associations between caregivers' chronic stress evaluated by hair cortisol concentrations (HCC) and obesity measures among children with disabilities such as autism.

METHODS

Eighty-five dyads of children with disabilities and their primary caregivers participated in the study between April and July 2013 in the Patagonia Region, Chile. Trained research staff conducted anthropometric measurements of children and caregivers. Cortisol concentrations, extracted from hair samples with methanol, were quantified using liquid chromatography tandem mass spectrometry. Pearson's correlation coefficients and linear regression models were used to examine the associations between caregiver HCC (log-transformed) and child obesity measures with adjustment for covariates.

RESULTS

Caregiver HCC were positively and significantly correlated with child weight (child age- and sex-adjusted r =0.23, P = 0.036), body mass index (BMI) (r = 0.23, P = 0.035), circumferences of neck (r = 0.30, P = 0.006), waist (r = 0.27, P = 0.014), and hip (r = 0.22, P = 0.044). After adjustment for children's age and sex, caregiver HCC were significantly related to child weight (kg) (beta = 4.47, standard error (SE) = 2.09), BMI (kg/m(2)) (beta = 1.52, SE = 0.71), neck circumference (cm) (beta = 1.20, SE = 0.43), waist circumference (cm) (beta = 3.75, SE = 1.50), and hip circumference (cm) (beta = 3.02, SE = 1.48). Caregiver HCC were also positively but not statistically significantly associated with child waist-to-hip ratio (beta = 0.01, SE = 0.01; P = 0.191) or body fat percentage (%) (beta = 2.11, SE = 1.28; P = 0.104). Further adjustment for other covariates including child disability diagnosis and caregiver age, sex, education, current smoking, perceived stress, and caregiver BMI did not change the results substantially.

CONCLUSIONS

Chronic stress of caregivers, evaluated by increased cortisol concentrations in hair, was positively associated with obesity measures among children with disabilities.

Creation of a reference dataset of neck sizes in children: standardizing a potential new tool for prediction of obesity-associated diseases?

Background

Neck circumference (NC), is an emerging marker of obesity and associated disease risk, but is challenging to use as a screening tool in children, as age and sex standardized cutoffs have not been determined. A population-based sample of NC in Canadian children was collected, and age- and sex-specific reference curves for NC were developed.

Methods

NC, waist circumference (WC), weight and height were measured on participants aged 6–17 years in cycle 2 of the Canadian Health Measures Survey. Quantile regression of NC versus age in males and females was used to obtain NC percentiles. Linear regression was used to examine association between NC, body mass index (BMI) and WC. NC was compared in healthy weight (BMI < 85^th percentile) and overweight/obese (BMI > 85^th percentile) subjects.

Results

The sample included 936 females and 977 males. For all age and sex groups, NC was larger in overweight/obese children (p < 0.0001). For each additional unit of BMI, average NC in males was 0.49 cm higher and in females, 0.43 cm higher. For each additional cm of WC, average NC in males was 0.18 cm higher and in females, 0.17 cm higher.

Conclusion

This study presents the first reference data on Canadian children’s NC. The reference curves may have future clinical applicability in identifying children at risk of central obesity-associated conditions and thresholds associated with disease risk.