Diet and Nutritional Status of Polish Girls with Rett Syndrome—A Case-Control Study

(1) Background: Rett syndrome may be considered a disease strongly associated with nutritional disorders that are likely to require special management strategies, extending beyond what is usually required for children with other developmental disorders. The aim of the study was to assess the nutritional status and diet of Polish girls with Rett syndrome. (2) Methods: Each patient (study group = 49, control group = 22) underwent anthropometric measurements, including body weight and height, waist, hip and arm circumference, and skinfold measurement. The assessment of the diet was based on the analysis of 7-day menus and the Food Frequency Questionnaire (FFQ-6). Data were analyzed using Statistica 13.3. (3) Results: The majority of the girls with Rett syndrome were deficient in weight and height, and consumed fewer calories, less protein, dietary fiber, calcium, and iron than the control group. They also drank less fluid. Soft products that were easy to chew and considered to be high in energy value were significantly more common in the menus. (4) Conclusions: Girls with Rett syndrome are characterized by weight deficiencies, poor growth that deteriorates with age, and are at risk of food shortages. Various nutritional intervention strategies should be explored to reduce and, if possible, prevent malnutrition and cachexia in such patients.


Introduction
Rett syndrome is a neurodevelopmental disorder caused predominantly by mutations in the MECP2 gene [1]. The classic form of the disease occurs only in female children [2]. The main features of the disease include a period of normal development, followed by regression, with the loss of communication skills and hand function, the development of hand stereotypies and impaired gait [3]. In addition, Rett syndrome is associated with epilepsy and scoliosis. Poor growth is also one of the symptoms accompanying this disease [4][5][6][7]. It is caused by a number of factors affecting food intake, including feeding difficulties (despite good appetite), oromotor dysfunctions and other gastrointestinal disorders, as well as factors probably determined by the genotype and being an integral part of the disease [8]. There are additional neurological complexities, such as apraxia, autonomic dysfunction, including hyperventilation, sleep pattern disorders, or the development of scoliosis, each of which may exert an effect on food intake and growth. Contrary to numerous other neurological disorders, Rett syndrome may be considered a disease strongly associated with nutritional status disorders that are likely to require special management strategies, extending beyond what is usually required for children with other developmental disorders [9]. Rett syndrome is rare (1/10,000-15,000 female live births) [10]. Most clinicians typically have very few patients, and there is limited literature on the nutritional management of the disease. Moreover, the anthropometric assessment of the nutritional status, the measurement of body height in particular, constitutes a problem in this group of patients because some of them are unable to stand on their own or have deformities of the spine [11]. The Polish Rett Syndrome Association (PRSA) currently unites 160 families who are raising a child with Rett syndrome. The PRSA is dedicated to promoting awareness of the disease among doctors, therapists and society. The Association is actively involved in the European Rett Syndrome Association (ERSA), the International Rett Syndrome Foundation (IRSF) and the Australian InterRett Project. Moreover, the goals of the PRSA include direct assistance to children and their caregivers and cooperation with the Ministry of Health [12]. The aim of the study was to assess the nutritional status and diet of Polish girls with Rett syndrome.

Materials and Methods
The study included 49 girls with Rett syndrome (study group) aged 8.7 ± 4.9 years and 22 healthy girls (control group) aged 10.7 ± 3.5 years. All girls in the study group were the wards of the Polish Rett Syndrome Association [12]. Patients for the study (study group) were recruited in June and July 2021, and the study was conducted in the autumn (October-December) of the same year. Patients with clinically diagnosed Rett syndrome confirmed by molecular testing were qualified for the study. The study group accounted for about 30% of the entire population of girls with Rett syndrome in Poland. The control group was recruited in January 2022 and the tests were carried out in February-March 2022. Healthy girls without any medical history were qualified. The control group was only a background for comparisons, because there are no studies on the nutritional status and diet of Rett syndrome in Poland. The study was conducted at the Department of Clinical Dietetics of the Medical University of Warsaw. The results of the study are part of the project entitled Comprehensive assessment of energy needs, nutritional status and diet of girls with Rett syndrome. The databases were prepared in April-November 2022. The examination was non-invasive and safe for the patient. The inconvenience was related to the need to come to the university and undergo an examination lasting about an hour.
Just under 50% (n = 25) of our patients have one of the six most common mutations in MECP2.
As most of the girls in our study were clinically stable and had reached the age of 3-4 years, the staging was 3, except for 3 out of 49 patients who, as judged by their young age, were defined as having stage 2 to 3 disease.
Gastrointestinal symptoms found in our patients included constipation and gastroesophageal reflux. Although probably of central origin, we have also included respiratory abnormalities, as these may mechanistically cause bloating and thus lead to upper alimentary tract disturbance. Twelve of 49 girls (24%) reported constipation, 11 (22%) had reflux disease, and 39% (n = 19) had respiratory abnormalities. The overlap of at least two of these features occurred in 15 girls (30%) in our cohort. Only one girl was PEG-fed.
In total, 14 out of 25 patients with one of the six common MECP2 mutations had one of the above gastrointestinal features.

Anthropometric Measurements
Each patient underwent anthropometric measurements, including body weight and height, waist, hip and arm circumference, and skinfold measurements: supra-iliac skinfold (SI), triceps skinfold (T) and subscapular skinfold (SS). Body weight was measured using the Radwag WPT 60/150 scales, with an accuracy of 100 g. If the patient could not stand unassisted on the scales, the measurement was performed together with the carer holding her, correcting the measurement for her body weight. The patient was weighed in light underwear. Body height was measured in the study group using an anthropometer with the patient in a lying position. The following measurements were taken: from the top of the head to the iliac spine, from the iliac spine to the knee joint space and from the knee joint space to the edge of the foot with an accuracy of 1 mm [13]. In girls who could stand unassisted and in the control group, the height was measured in a standing position with the use of a stadiometer with an accuracy of 1 mm. The circumferences were measured with a tailor's tape, and the skinfolds were measured with the use of the Harpenden caliper with an accuracy of 1 mm. Waist circumference was measured at the location of the smallest circumference of the trunk, between the lower edge of the lowest rib and the upper edge of the iliac ala. The circumference of the hips was measured at the site of the largest circumference of the buttocks below the iliac alae. Skinfolds were measured on the non-dominant side of the body, three times, calculating the mean. The circumference of the arm was measured at midarm (between the acromion and the condyle of humerus) with an accuracy of 1 mm.

Assessment of Nutrition
The assessment of the diet was based on the average intake for 7 days, comprising weekend days and the vitamin and mineral supplementation used, as well as oral nutrition support (ONS). The data from the menus were verified by a qualified dietitian who clarified and supplemented them during the interview. The FFQ-6 questionnaire was also analyzed to assess the frequency of consumption of products over 12 months. The information obtained from the FFQ-6 was interpreted by converting the original food frequency categories into semi-quantitative data that logically reflect the increasing intensity of the trait using their ranking, i.e., assigning the food frequency categories to conventional integers and converting them into real numbers, and expressing the food consumption frequency as times/day [18] (Table 1). The data from the menus were evaluated using Dieta 6.0 program (developed by the National Institute of Public Health PZH-PIB in Poland). The obtained data were compared to nutritional reference values for the Polish population [19].

Statistical Methods
Descriptive statistics were performed using Statistica 13.3. Since most of the analyzed variables did not have a normal distribution (verified with the Lilliefors and Shapiro-Wilk tests), the data were presented as the mean, standard deviation (SD), median, quartiles and interquartile range (IQR). Differences in individual intergroup parameters were calculated using the Mann-Whitney U test, and the correlations between selected anthropometric variables with the Spearman's rank correlation. The level of statistical significance was assumed at p < 0.05.

Approval of the Bioethical Committee
The study was approved by the Medical University of Warsaw Bioethical Committee (approval number KB/145/2021). Informed consent was obtained from all subjects involved in the study.

Assessment of Nutrition
The diets of girls with Rett syndrome significantly more commonly included soft products perceived as providing a high energy value, i.e., bananas (average times/day:  Table 4).

Dietary Intake
The diets of girls with Rett syndrome were characterized by a significantly lower energy value (median: 1248.5 kcal/d vs. 1683.9 kcal/d, p = 0.04) and carbohydrate content (181.6 g/d vs. 257.0 g/d, p < 0.001), including: starch (72.1 g/d vs. 132.3 g/d, p < 0.001), sucrose (39.2 g/d vs. 52.4 g/d, p = 0.04) and dietary fiber (11.7 g/d vs. 16.9 g/d, p = 0.00), compared to those in the control group. The percentage of people implementing the reference values for energy consumption in both groups was: 26.5% (n = 13) and 31.8% (n = 7), respectively (Tables 5 and 6). However, the average implementation of reference values for certain minerals and vitamins was significantly higher in the study group. This included in particular: potassium (%AI: 124. 12.4, p < 0.001. When the daily intake of nutrients was converted into kg of body weight (kg b.w), it was found that girls with Rett syndrome consumed statistically significantly more of each of the analyzed macro and micronutrients, including sodium, saturated fatty acids, sucrose, cholesterol, dietary fiber and water (for example: energy-63.3 kcal/kg b.w vs. 46.4 kcal/kg b.w, p < 0.001, protein-2.5 g/kg b.w vs. 1.7 g/kg b.w, p < 0.001, fat-2.0 g/kg b.w vs. 1.2 g/kg b.w, p < 0.001, carbohydrates-8.9 g/kg b.w vs. 6.9 g/kg b.w, p = 0.017, sodium-107.5 mg/kg b.w vs. 79.1 mg/kg b.w, p < 0.001, SFA-0.9 g/kg b.w vs. 0.5 g/kg b.w, p < 0.001, sucrose-2.  (Table 5). Moreover, the percentage of individuals whose diets were compliant with the recommendations for the above mentioned ingredients was higher in the study group (Table 6) and this was mainly due to the increased use of supplements of those vitamins and ONS. The diets of control group girls contained higher amounts of polyunsaturated fatty acids (6.4 g/d vs. 4.3 g/d, p = 0.00), mainly including the n-6 family (5.5 g/d vs. 3.3 g/d, p = 0.00). Despite the significantly lower energy value of the diet, the percentage of proteins and fats in it was significantly higher in the diets of girls with Rett syndrome than in the control group: %E from protein (16.6 vs. 15.6, p = 0.02), %E from fats (28.4 vs. 24.7, p = 0.01) ( Table 5). A low percentage of girls in the study group received a suitable amount of fluids (18.4% vs. 31.8%) ( Table 6).
The existence of significant correlations between BMI z-score, arm circumference, muscle mass and other nutritional status indices was demonstrated in both the study and control groups (Tables 7 and 8). Such correlations were not observed with regard to dietary intake.
In the study group a significant, negative correlation was also observed between age and body mass index (r = −0.36, p = 0.01) (Figure 1). In the study group a significant, negative correlation was also observed between age and body mass index (r = −0.36, p = 0.01) (Figure 1).

Discussion
The majority of the anthropometric parameters of girls with Rett syndrome were significantly lower than in the control group, which particularly applied to weight and height. Measuring body weight in this type of condition is considered a critical part of clinical evaluation because measuring body height is more problematic, especially since some girls or women are unable to stand on their own or had spinal deformities, while the mere comparison of body weight cannot be concluded without reference to body

Discussion
The majority of the anthropometric parameters of girls with Rett syndrome were significantly lower than in the control group, which particularly applied to weight and height. Measuring body weight in this type of condition is considered a critical part of clinical evaluation because measuring body height is more problematic, especially since some girls or women are unable to stand on their own or had spinal deformities, while the mere comparison of body weight cannot be concluded without reference to body height, poor height gain and a comparison with a healthy population, also in the studies of other authors, seem to confirm significant deficiencies in the group of girls with Rett syndrome [11]. Few studies are available on the management of poor height gains in Rett syndrome, but they confirm the existing problem and the deterioration of parameters with age [6,7,[20][21][22]. Although two people with extreme obesity were identified in the group of Polish girls with Rett syndrome, significantly more patients had BMI below the reference ranges for age and sex (48.9% vs. 13.6%). Similarly to the results published by other authors, the median BMI z-score was also lower than in the control group and BMI significantly decreased with age [7,20,21]. The analyses performed only compare individual variables between groups, and the influence of other factors cannot be completely excluded.
Regrettably, due to very common concomitant epilepsy, most girls with Rett syndrome cannot undergo the assessment of body composition using the method of electrical bioimpedance, which is a simple, accurate and non-invasive study evaluating parameters such as energy resources. Therefore, it may be important to measure the circumference of the arm and skinfolds and calculate their body composition, including energy resources, in assessing nutritional status. Arm circumference is a useful measure of body fat and lean mass, especially in children up to 5 years of age. It is particularly useful when body weight is not a reliable determinant of nutritional status (e.g., swelling, dehydration, chronic glucocorticoid therapy-GCS) or when a reliable measurement of body length/height cannot be obtained [16]. Energy resources of patients with Rett syndrome calculated on the basis of skinfolds were not large, but in most cases they were similar or within the normal limits commonly adopted for girls from the general population (>19%). The median of %FAT was lower than control group but the difference was not statistically significant, while the muscle mass and the muscle circumference of the arm were significantly lower in the study group than in the controls. However, there was a significant positive correlation with other anthropometric parameters, such as body weight, BMI z-score, waist circumference, hip circumference, %FAT and muscle mass. This confirms their usefulness in assessing the nutritional status in patients with Rett syndrome, especially in case of difficulties in performing some measurements using standard methods used in a healthy population.
According to Australian researchers who recruited an international panel of experts, analyzed the available literature and developed recommendations for parents and clinicians dealing with Rett syndrome, the assessment of energy requirements should be based on serial measurements of body height, but in case of underweight patients, energy requirement should exceed the recommended calorie intake for body weight [11]. Energy-dense foods are the best way to increase calorie intake. Snacks containing high-calorie products and high-calorie ONS can also be served [2,23,24]. Other authors also emphasized that most girls with this condition required crushing or mashing of products to make eating easier, which was confirmed by our research [7]. The diets of girls with Rett syndrome significantly more commonly included soft products which were easy to crush and perceived as providing a high energy value, i.e., bananas, potatoes or root vegetables in soups, as well as products providing a large amount of protein, i.e., cold cuts, cottage cheese and eggs. However, the diets of girls with Rett syndrome were characterized by a significantly lower energy value and carbohydrate content, including starch, sucrose and dietary fiber, compared to those in the control group. The diets of the majority of girls with Rett syndrome did not meet the nutritional standards for energy, iron and calcium. However, most of them complied with the norm for the intake of protein, sodium, potassium, phosphorus, magnesium, zinc and vitamins B 1 , B 2 , B 6 , B 12 , D. When the daily intake of nutrients was converted to kg of body weight (kg b.w), it was found that girls with Rett syndrome consumed statistically significantly more of each of the macro-and micronutrients analysed than the control group. This was mainly due to the more frequent use of supplements of vitamins and ONS. A low percentage of girls in the study group received a suitable amount of fluids. Similar data were reported by other authors. Most of the cohort studied by Chin et al. [22] had adequate protein and energy intake. Fiber intake was generally low in this group, and most individuals did not reach the daily reference intake. Protein intake was significantly lower in people with severe growth deficiency. Nevertheless, almost a third of the people participating in the study ate more than expected and less than a quarter ate less than expected. The low intake of fluids was a cause of concern. A study by Schwartzman et al. [2] showed no significant correlation between protein intake with diet and body height. Insufficient iron and calcium intake was observed. Motil et al. [6] found that the parents of the study participants reported that their children had a "good appetite", although the total energy and calcium intake was significantly lower than the reference values for height and age.
Patients with Rett syndrome usually have a good appetite, and deficiencies in body weight and height are very often due to symptoms associated with the disease, such as holding breath, hyperventilation, hand stereotypies, upper body swaying, or feeding disorders requiring crushing, chopping or blending of food, and depend on the mobility of patients [11,21]. There is also prolonged feeding time, gagging or choking with food or liquids, and some patients require enteral nutrition support [7]. Poor feeding skills, including difficulty in chewing and swallowing food, and involuntary tongue movements, possibly due to altered muscle tone and dyspraxia, as well as poor motor control, excessive salivation, hyperventilation, and holding breath, may further interfere with feeding [7,25]. These difficulties are compounded by poor communication skills, which make it difficult for patients to express what or how much they want to eat. As a result, fewer calories may be consumed than are necessary for growth and development. One should also be aware of possible additional energy requirements associated with involuntary activities, including hand stereotypies and autonomic system abnormalities, including hyperventilation or breathing disorders. However, this has not been confirmed in clinical trials so far [11].
Thin liquids are the most challenging for patients with swallowing disorders because they flow quickly to the pharynx and require adequate lip closure, sensorimotor regulation and/or complete closure of the laryngeal vestibule [26]. Bianco and Rota [27] in their review indicated that children with RS present high-arched palate, oral breathing, sialorrhea, poor tongue movements, and open bites, which influence not only the oral phase of swallowing but also the pharyngeal. It is probable that common breathing abnormalities presented by RS girls may impact swallow safety [28]. Breathing-swallowing discoordination results from prolonged swallow latency, delayed timing of following sequences of swallowing, and breathing irregularities or hyperventilation [29]. Untreated malocclusion may also be associated with dysphagia severity in RS patients [30]. The described disorders may lead to an increased risk of aspiration (including silent without cough response), especially with thin liquids [31,32]. Presumably, insufficient fluid intake in our patients resulted from fluid avoidance by children or caregivers due to fear of choking or aspiration or extended efforts paid to fluids swallowing. However, little is known about the exact prevalence, severity, mechanism, and treatment of swallowing disorders in RETT syndrome patients [33].
Based on the reviewed literature, it seems that a diet containing the recommended daily intake of essential nutrients is optimal and should be given during frequent small feedings offered during the day. People at risk of the deficiency of certain micronutrients, e.g., those taking certain anticonvulsant drugs, poorly growing, with symptoms suggestive of malabsorption from the gastrointestinal tract or satisfying at least 50% of nutritional needs by enteral route, are recommended to undergo folic acid and vitamin B 12 tests and possible supplementation should be considered [11].
Rett syndrome is a complex and overwhelming disorder. A multi-aspect medical treatment should be introduced using the knowledge of specialists working in multidisciplinary teams including a dietitian, because there is a lack of peer-reviewed literature with high scientific value in this area.
The limitation of our study was the inability to perform detailed body composition tests (e.g., BIA) due to comorbidities such as epilepsy. It would also be worth including the determination of markers of nutritional status in the blood and the saturation of the body with vitamins and minerals before a possible change in diet. The strength of our study was proving that the simple and cheap methods we used to assess nutritional status were good and useful and minimally invasive, especially if other methods, such as BIA, cannot be used because of epilepsy. The nutritional analysis of Polish girls with Rett syndrome is a groundbreaking study that will allow for better dietary planning and supplementation of this group of patients in order to prevent nutritional status disorders and other dietrelated disorders, such as constipation and reflux, which are common in this group, which will improve the patients' quality of life. It will also enable the development of national guidelines for nutritional management in this group of patients. This paper demonstrates the potential of outcomes research to provide a methodology for identifying what is needed to enable healthcare professionals to provide the right nutritional care for patients with Rett syndrome.

1.
Girls with Rett syndrome have reduced weight, poor growth that deteriorates with age, and are at risk of nutritional deficiencies.

2.
Various nutritional intervention strategies should be explored to reduce and, if possible, prevent malnutrition and cachexia in girls with Rett syndrome.

3.
There is a need to systematically review the literature and gather expertise to identify current best practices in relation to nutritional assessment and management. Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.
Data Availability Statement: Data will be released upon the request of the data subject. The data are archived in the database of the Medical University of Warsaw.