https://doi.org/10.1186/s40337-021-00445-1, DOI: https://doi.org/10.1186/s40337-021-00445-1. Rocks T, Pelly F, Wilkinson P. Nutritional management of anorexia nervosa in children and adolescent inpatients: the current practice of Australian dietitians. At day 10, VO2 (R=0.59, P=0.04) was correlated with GNG and VCO2 with EGP (R=0.85, P=0.00003). Weight loss of more than 10 percent of his or her body weight in the past 3 to 6 months; Little to no food for the past 5 or more consecutive days; or. Refeeding Syndrome: Prevention and Management Sydney Childrens Hospital Practice, Guideline June 2013 Crook MA. Fiber intake depends on age, gender, and sex. Eur Eat Disord Rev. WebBACKGROUND. Previous systematic reviews [2,8] showed that studies on RFS were highly heterogenous since most definitions were based on blood electrolyte disturbances, mainly refeeding hypophosphatemia (RH), while others considered the presence of overt signs and symptoms as well (i.e., edema, respiratory or heart failure). The National Institute for Clinical Excellence has produced guidance for providing nutrition recommending a graded approach [15]. Refeeding syndrome is a serious and potentially fatal condition that can occur during refeeding. 2002;159(8):134753. Four studies reported weight gain primarily in the context of ED YP with medical instability [24,25,26, 44]. Crook MA, et al. https://doi.org/10.1002/erv.2614. 2018;26(5):51925. Maginot et al., 2017 [18] and Whitelaw et al., 2010 [9] reported NG bolus feeding in 13.8 and 15% in order to supplement oral diet with a mean weight gain of 3.1kgs and 2.6kgs respectively but did not report if this was specific to NG feeding. 2014;68(2):1717. Refeeding syndrome is a severe complication of refeeding in people with malnutrition, it includes a series of electrolyte disorders and clinical symptoms. The entity of electrolyte depletion and the presence of organ dysfunction allow to define the severity of the syndrome [1]. Clausen L, Larsen JT, Bulik CM, Peterson L. A Danish register-based study on involuntary treatment in anorexia nervosa. Skipper. In the UK, three studies described NG use during medical instability after oral intake was refused [27, 28, 40] and one where oral intake was inadequate [31]. If the SMI increased, the odds for pleural effusion and pleural empyema decreased, but the odds of a pulmonary embolism increased. Compared to other mental illnesses, EDs have a high mortality rate with young people (YP) with anorexia nervosa (AN) on average 610 times more likely to die than the general population [4, 5]. Couturier J, Mahmood A. It is evident that there is a wide variety of practices regarding implementation and regime of NG feeding in YP with eating disorders globally [9]. Clinical Nutrition (2002) 21 (6): 515-520. Terms and Conditions, American Psychiatric Association. This causes insulin secretion to increase. Privacy Other factors can also put you at an increased risk of developing refeeding syndrome. A blood test that reveals low levels of phosphorus, potassium or magnesium. Univariate, unadjusted long-term survival analysis revealed that lower MRA and lower SMI were associated with shorter survival (P=0.03). The refeeding syndrome (RFS) is described as a set of metabolic and electrolyte alterations occurring as the result of the reintroduction of calories through oral, enteral, parenteral nutrition after a period of consistent reduction of energy intake or starvation in individuals with pre-existent malnutrition and/or in a catabolic state [ [1], (NICE Guideline, No. Preventative therapies: Thiamine 100-200 mg q12-24. There are no other acknowledgements to be made. 2015;45(2):41527. NICE. In the circumstances that their BMI is detrimentally low, a nasogastric (NG) tube may be placed from nose to stomach to pass nutrition. Healthline Media does not provide medical advice, diagnosis, or treatment. In other words, the lower a patients weight, the higher their risk for this complication during refeeding. In studies where continuous NG was provided, YP were sometimes not given the option of an oral diet so that their calorie intake could be closely monitored [22,23,24, 31]. NG was also implemented due to acute refusal of food or inability to meet oral intake, without significant medical instability, in five studies [9, 10, 18, 31, 43]. Agostino H, Erdstein J, Di Meglio G. Shifting paradigms: continuous nasogastric feeding with high caloric intakes in anorexia nervosa. This preliminary exploratory study shows that GNG and EGP have different predictors on days 4 and 10; EGP is more correlated with the metabolic level, while GNG is dependent on external factors. How to Gain Weight Fast: Tips to Be Safe and Healthy, Diabulimia: Why This Eating Disorder Is So Dangerous for People with Diabetes. If this is tolerated, continue to gradually increase intake up to full nutritional support. The The majority also had a relatively small sample size, again introducing the possibility of bias and reducing generalizability. Nasogastric feeding (NG) is a method of enteral nutrition often used in inpatient settings to treat medical instability, to supplement poor oral intake or to increase nutritional intake. There are many vegan protein powders on the market, with a variety of flavors and ingredients available. It is not possible from this review to discern the advantages and disadvantages of each method as no study made a direct comparison. Federal government websites often end in .gov or .mil. The pooled effect of higher calorie intake of 1234 patients in 8 studies was WMD=3.04 (95% CI,5.10 to0.99, P=0.003) days. Early RFH was defined as serum/plasma phosphate <0.65mmol/L and a drop of >0.16mmol/L within 3 days of admission to the PICU. Together, these processes can lead to decreased concentrations of minerals in the blood, of which hypophosphatemia is the most characteristic [14]. They are at even greater risk of precipitate falls in these circulating electrolytes once simultaneous nutritional and fluid therapy has started. WebRefeeding syndrome consists of metabolic changes that occur on the reintroduction of nutrition to in those who are malnourished or in the starved state (Figure 1). specialist registrar gastroenterology and clinical nutrition. In Australian based studies, NG was given due to refusal of oral intake in 2 studies [9, 10] as well as to treat medical instability [26]. Inclusion terms were: enteral feeding by nasogastric tube, under 18years, eating disorders, and primary research. To examine the impact of nutritional intake on phosphate concentrations, structural nested mean models with propensity score and censoring models were used. WebThese consensus recommendations are intended to provide guidance regarding recognizing risk and identifying, stratifying, avoiding and managing RS. Refeeding Syndrome: Problems with Definition and Management. 1). Andrea Evangelista: Formal analysis; Software. For this reason, acute medical intervention is often warranted in order to reduce mortality. KH gathered data and interpreted results. Refeeding the malnourished patient: Lessons learned. Its caused by sudden shifts in the electrolytes that help your 2011;19:52630. Nutritional rehabilitation is central to achieving medical stabilization. CF performed the discussion. Recent guidance from the British Dietetic Association [14] for NG feeding under restraint advised 12 bolus feeds per day even in those with high risk of refeeding syndrome (RS); it also concluded further research into this area was required. Until recently, refeeding syndrome (RFS) has lacked standardized diagnostic criteria. The evolution of all aspects of HPN is presented. Any discussion on the risks of the refeeding syndrome should include the increased threat of infection that may often be silent in malnutrition.1 Malnourished patients may develop infection without showing the usual septic markerssuch as an increased temperature, leucocyte count, or C reactive protein. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. PubMed 2019;8(3):1248. Long-term effects of enteral feeding on growth and mental health in adolescents with anorexia nervosa--results of a retrospective German cohort study. Neiderman M, Farley A, Richardson J, Lask B. Nasogastric feeding in children and adolescents with eating disorders: toward good practice. (2004). Manage cookies/Do not sell my data we use in the preference centre. The PRISMA flowchart was used (Fig. 1985;102(1):4952. Our multivariate model could predict EGP at day 4 (VCO2, glucose and energy intake) with an error coefficient (e.c.) Nasogastric (NG) feeding use in YP with ED may be used as a lifesaving treatment when patients are physically unwell [7, 8]. By comparison, IO only resulted in 6469% BG in range across different nutrition types. Refeeding syndrome affects the length of stay in part of, but not all, patients. In 2018, the ACUTE Center for Eating Disorders & Severe Malnutrition at Denver Health was honored by Anthem Health as a Center of Excellence for Medical Treatment of Severe and Extreme Eating Disorders. 2005;13(4):26472. Some described NG feeds as easier than eating as it disguised the amount due to not swallowing; others felt it was a form of punishment for not gaining enough weight. Ann Intern Med. This exploratory study is based on the data from the Supplemental Parenteral Nutrition study 2 (SPN2), which measured EGP and GNG at days 4 and 10 in 23 critically ill patients. DOI: Hearing SD. DOI: Lambers WM, et al. In this cross-sectional study, we analyzed plasma SCFA levels, HIF3A expression, and CpG methylation of HIF3A intron 1 in peripheral blood from patients with type 2 diabetes presenting with (n=92) and without (n=105) cardiomyopathy. https://doi.org/10.7748/ns.2017.e10509. Enteral nutrition via nasogastric tube for refeeding patients with anorexia nervosa: a systematic review. Agostino and colleagues [23] demonstrated that YP on medical wards having NG feeds had a mean LOS of 33.8days compared to those in the same setting having an oral diet who had a mean of 50.9days, however, the oral diet was lower in calories therefore taking longer for weight recovery and medical stabilisation. WebThiamine Supplementation in Treatment of Refeeding Syndrome 39 for refeeding syndrome, 100 mg of thiamine is METHODS recommended before initiating feeding or IV uids and 100 mg/day for 5 to 7 days or longer Given the paucity of data on thiamine in patients with severe starvation, chronic supplementation and refeeding syndrome, a People who are at risk of heart-related complications may require heart monitoring. However, it typically follows a period of: Certain conditions may increase your risk for this condition, including: Certain surgeries may also increase your risk. 11 Historically, recommendations for nutritional rehabilitation in inpatient settings have been conservative, 12 16 for fear of precipitating the refeeding syndrome, a constellation of electrolyte disturbances and multiorgan dysfunction that can develop early in the The aim of this systematic review and meta-analyses was to estimate the incidence of RFS in adults by considering the definition used by the authors as well as the recent criteria proposed by the American Society of Parenteral and Enteral Nutrition (ASPEN) consensus. Med J Aust. Int J Adolesc Med Health. The most common primary disease was cancer (n=267), followed by mesenteric ischemia (n=104), and surgical complications (n=62). As early RFH might impact recovery, it is important to closely monitor phosphate concentrations in patients, especially of those at risk for early RFH. Structured, supported feeding admissions for restrictive eating disorders on paediatric wards. After electrolyte levels stabilize, increase caloric intake to 40 kCal/hr for a day, then increase to 60 kCal/hr for a day. 2016;2016:19. Healthcare professionals can prevent complications of refeeding syndrome by: Refeeding syndrome appears when food is introduced too quickly after a period of malnourishment. government site. The inclusion criteria were: NG feeding, participants under 18years, eating disorders, published since 2000 and primary research. These include: Refeeding syndrome can cause sudden and fatal complications. 2019;115(12):501. California Privacy Statement, Earley T. Improving safety with nasogastric tubes: a whole-system approach. Overall, these manifestations are variable and insensitive tools for detecting refeeding syndrome. Eating Disorders: Recognition and Treatment. Therefore, a universally accepted definition for RFS, taking different clinical contexts and groups of patients into account, is still needed to better characterize the syndrome and its approach. Kezelman and colleagues (Australia) 2018 [26] assessed the impact on anxiety, depression and ED symptoms when using NG in adjunct to oral intake as part of a rapid refeeding regime. Globally studies from North America [18, 21, 39, 41] and Turkey [36] focused on medical instability in YP with ED. sharing sensitive information, make sure youre on a federal Guidelines help identify patients at elevated risk for developing this life-threatening complication of reintroducing calories in the early stages of anorexia nervosa treatment. It is necessary to adapt to the changing circumstances. It's unclear whether IV thiamine is absolutely required here, or whether oral thiamine would be adequate. Refeeding syndrome is a potentially fatal complication which generally occurs within 24-72 hours after starting nutrition (although it may occur later on). Many sources recommend starting conservatively (e.g., 50% energy requirement), with gradual advancement. Front Psychol. To evaluate the influence of the SMI and MRA on post-surgery complications, logistic regression models were used. Madden S, Miskovic-Wheatley J, Wallis A, et al. Refeeding syndrome is a serious and potentially fatal complication of nutritional rehabilitation in patients with severe anorexia nervosa. 2013;53(5):5904. Our results suggest that a robust model might be built, but requires a prospective study including a larger number of patients. Increasing awareness and using screening programs to identify those at risk of developing refeeding syndrome are the next steps in improving the outlook. It offered the unique chance to present how to create and grow the IF center, increasing the quality of care. A variety of different feeding regimes were identified in this review which are summarised in Table2. Conversely the YP in Paccagnella and colleagues [20] research stated NG was helpful, particularly initially when an oral diet was challenging to manage. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. By using this website, you agree to our RS can manifest as hypophosphatemia (HP), hypomagnesemia, hypokalemia and other electrolyte imbalances that result in cardiac arrhythmias, seizures and in some cases sudden death [18]. In 13 studies (3 high risk of bias [28, 35, 47]) in which NG was not implemented as standard protocol for all patients, the percentage of ED YP administered NG feeding in all contexts (due to medical instability or inadequate oral diet) varied between 6 and 66% [9, 18, 29, 31, 36, 37, 41,42,43,44]. A broader view of electrolyte shifts may be a welcome addition, given that prior definitions have focused excessively on phosphate. Source: Garber AK, Cheng J, Accurso EC, et al. Learn how to gain weight fast and healthily with these tips. Three studies were qualitative interview studies, examining patient or staff feelings towards NG feeding in practice which increases the risk of confirmation bias. Nasogastric tube feeding in line with new dietetic guidelines for the treatment of anorexia nervosa in a specialist children and adolescent inpatient unit: a case series. If phosphate falls <1.5 mg/dL (0.5 mM) this indicates refeeding syndrome > see treatment below. Three studies reported weight gain in the context of inadequate oral intake [9, 18, 39]. Agostino and colleagues [23] delivered nutrition on a medical ward solely via NG for 14days before commencing oral diet in addition to NG feeding. This systematic review sets out to Moreover, for clinicians, there is currently conflicting guidance on how to manage NG feeding in YP with ED, in particular how and when to transition between oral and NG feeding [20, 21]. Nehring and colleagues [37] concluded that NG feeding had no impact on growth, recovery or development of psychiatric co-morbidities. 58% of the studies included only examined the effect of NG feeding as a secondary outcome of their study. The novel associations between plasma butyric acid levels and HIF3A intron 1 methylation at CpG 6 may highlight an underlying mechanism by which the microbial-myocardial axis and hostmicrobe interactions may participate in the pathogenesis of DCM. Nutritional glucose intake affects blood glucose (BG) outcomes, but few protocols actively control it. Mehanna HM, et al. No study reported a YP developed RS. The epigenetic regulation of the hypoxia-inducible factor 3A (HIF3A) gene is implicated in oxidative metabolism in the pathogenesis of diabetes. The use of enteral nutrition in the treatment of eating disorders: a systematic review. Previous studies indicate that the incidence of refeeding syndrome is relatively high [12], including electrolyte abnormalities with sodium-water retention, which may potentially lead to heart and respiratory failure, even death [11,13,14]. Catabolic state (e.g., due to infection or surgery). Treatment of patients with eating disorders. Agostino et al [23] compared a higher calorie (1500-1800kcal/d) continuous NG fed cohort to lower calorie oral bolus cohort (1000-1200kcal/d, divided 6 times per day), results showed mean weight gain was greater in the continuous NG fed group (1.22 kgs per week) than the oral bolus fed group (0.08 kgs per week) over the first 2weeks. Am J Psychiatry. https://doi.org/10.1002/eat.22968. 2019;34(3):35970. 167 (prepared by the Duke University evidence-based practice center under contract no. A blood test has revealed your serum phosphate, potassium, or magnesium levels are low. The .gov means its official. Complications of refeeding syndrome can be prevented by electrolyte infusions and a slower refeeding regimen. Gradual initiation of nutrition for the highest risk patients. Though some people who are at risk dont develop symptoms, theres no way to know who will develop symptoms before beginning treatment. On single-stage analysis, the strongest correlations were noradrenaline dose at day 4 with GNG (R=0.71; P=0.0004) and Nutrition risk screening score (NRS) with EGP (R=0.42; P=0.05). official website and that any information you provide is encrypted One of the main guidelines used for the evaluation and treatment of refeeding syndrome is the National Institute for Health Care and Excellence (NICE) Dysphagia or hyperemesis. A systematic review of approaches to refeeding in patients with anorexia nervosa. https://doi.org/10.1002/eat.22482. The risk of bias was estimated into high, medium or low using an adapted version of the Agency for Healthcare Research and Quality risk of bias tool as described in Myers [34] which included an assessment of the bias in the selection of participants, sample size, tools used to assess change and whether the study involved blinding. The https://doi.org/10.1038/ejcn.2013.244. Research is still needed to determine the best way to treat refeeding syndrome. Refeeding syndrome: What it is, and how to prevent and treat it. However, if the analysis was adjusted for confounders, e.g., Charlson Comorbidity Index, no relevant association regarding long-term survival was detected. Sometimes called the hot dog of the sea, imitation crab is a popular ingredient in dishes like seafood salads, crab cakes or California sushi rolls, Protein is essential for building and maintaining muscle mass but consuming too much can negatively affect your health. Supplemental nocturnal nasogastric refeeding for better short-term outcome in hospitalized adolescent girls with anorexia nervosa. Application criteria of enteral nutrition in patients with anorexia nervosa: correlation between clinical and psychological data in a lifesaving treatment. (2015). Extended period NPO (>5 days). Routine NG feeding may allow greater initial caloric intake, which does not increase risk of medical complications, and may actually increase initial weight gain thus reducing time in hospital. However, due to the high heterogeneity of data, summary incidence measures are meaningless. Results have shown that NG feeding is used commonly in the hospital setting to treat medical instability as a result of severe malnourishment, and in the specialist eating disorders (ED) unit due to failure to meet oral intake. Cycle electrolytes (including phosphate, magnesium, and potassium). If youre recovering from an eating disorder or wanting a more positive relationship to food, these apps can. https://doi.org/10.1002/erv.624. Garber AK, Sawyer SM, Golden NH, Guarda AS, Katzman DK, Kohn MR, et al. As a result, prevention is critical. The repletion of calories should be slow and is typically at about 20 calories per kilogram of body weight on average, or around 1,000 calories per day initially. The results of this review support the conclusions from Rizzo and colleagues [49] (2019) that NG feeds can be safely administered and have the advantage of shortening LOS when used to increase total caloric intake. Int J Eat Disord. (2001). Webreport, literature review and clinical guidelines. A systematic review following PRISMA guidelines was conducted by searching AMED, EMBASE and MEDLINE databases from 2000 to 2020. Street K, Costelloe S, Wooton M, Upton S, Brough J. Meal support therapy reduces the use of nasogastric feeding for adolescents hospitalized with anorexia nervosa. Available from: https://www.ncbi.nlm.nih.gov/books/NBK436876/. One article published prior to 2000 was included in the full text review due to it requiring translation prior to assessing it against the criteria. https://doi.org/10.1002/ncp.10187. WebRefeeding syndrome is defined as the potentially fatal shifts in fluids and electrolytes that may. WebNephrotic syndrome . These studies discussed ceasing NG feeds after the risk of RS had reduced; most gave a time frame between 2 and 14days [24, 44]. EDs usually manifest prior to adulthood, with an average age of onset of approximately 15years, although this is decreasing; with new research from NICE demonstrating that incidence in children aged 12 and under had increased between 2005 and 2015 in the UK [2, 3]. Previous reviews [32, 33] have examined use of NG feeding in ED, including the safety and efficacy of NG feeding as well as short-term and long-term outcomes. Studies using bolus feeds stated that oral intake was encouraged and it was only when this was not fully achieved that supplementary NG was used [39]. A systematic review of the published literature was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [15]. 2017;5(1):110. Unfortunately, owing to the high heterogeneity of data, summary incidence measures are meaningless. Refeeding syndrome is an important complication of refeeding in previously malnourished patients [11]. Most EDs will be treated in an outpatient setting with hospitalisation generally reserved for those with severe malnutrition resulting in physical symptoms such as bradycardia, hypotension or dehydration as set out in the MARSIPAN guidance [16]. Child and adolescent mental health service, Preferred Reporting Items for Systematic Reviews and Meta-Analyses, National Guideline Alliance (UK). Valentina Ponzo: Data curation, Writing - Review & Editing. They concluded that the requirement for NG was an indication of severity and resistance to oral feeding [44]. A number of YP in MH wards required restraint to NG feed with one study reporting this was required for 66% of YP [24]. Refeeding syndrome: A literature review. If you're underweight and looking to gain weight, it's very important to do it right. 314 patients (51.8%) died. Our study suggests more standardized methods of caloric intake are needed in resource-limited settings with high co-prevalence of PEM and TB. 86% of studies were deemed high or medium risk of bias due to the type of study: 34.4% retrospective cohort and 10.3% RCT; 17.2% were qualitative. Moreover, refeeding syndrome is seems to be associated with increased 6 months mortality [15]. When food is reintroduced, theres an abrupt shift from fat metabolism back to carbohydrate metabolism. Two studies [37, 43], found NG feeding was more likely to be required in: patients of a lower age at admission (14.3years compared to 15.3yrs. 3677-3687, Clinical Nutrition, Volume 40, Issue 6, 2021, pp. AHRQ publication no. the founding of the HPN center and its further development is possible provided that there is team of dedicated people, supported by hospital base. (3) Absence of another obvious cause of hypophosphatemia that is felt to account for the hypophosphatemia. Bias can also occur due to the different treatment groups being recorded at different times thus confounding variables may include different staff working at the setting and therefore different methods of treating YP. https://doi.org/10.1002/eat.1040. There was no disagreement between CF and KH who assessed which studies were included. Significant discrepancy (>700 calories) was noted between nurse-estimated caloric intake compared to digital images. Results interpreted from studies with a high risk of bias were removed accordingly, leaving only high quality results and conclusions. WebRefeedingSyndromeDefinitionandBackground. Our unpublished survey of doctors, nurses, pharmacists, and dietitians (all members of their respective nutrition societies) on their attitudes to the guidance from the National Institute for Health and Clinical Excellence (NICE)2 showed widespread disparities in practice. 3787-3792, Clinical Nutrition, Volume 40, Issue 6, 2021, pp. YP with ED requiring NG were often medically unstable on admission [9, 18, 20, 22, 23, 25, 39] and NG feeding was implemented as standard practice [22, 23, 26, 39]. Eur J Clin Nutr. Predictive factors of length of inpatient treatment in anorexia nervosa. A systematic review and meta-analyses of literature, https://doi.org/10.1016/j.clnu.2021.04.023, ESPEN guideline on clinical nutrition in the intensive care unit, Restricted versus continued standard caloric intake during the management of refeeding syndrome in critically ill adults: a randomised, parallel-group, multicentre, single-blind controlled trial, Death resulting from overzealous total parenteral nutrition: the refeeding syndrome revisited, Refeeding syndrome in adults receiving total parenteral nutrition: an audit of practice at a tertiary UK centre, The risk of refeeding syndrome among severely malnourished tuberculosis patients in Chhattisgarh, India, Refeeding hypophosphataemia is more common in enteral than parenteral feeding in adult in patients, Incidence and outcome of refeeding syndrome in neurocritically ill patients, Impact of caloric intake in critically ill patients with, and without, refeeding syndrome: a retrospective study, Patients at risk of malnutrition: assessment of 11 cases of severe malnutrition with individualised total parenteral nutrition, COPD patients with acute exacerbation who developed refeeding syndrome during hospitalization had poor outcome: a retrospective cohort study, Refeeding syndrome in patients with gastrointestinal fistula, Management and prevention of refeeding syndrome in medical inpatients: an evidence-based and consensus-supported algorithm, Revisiting the refeeding syndrome: results of a systematic review, Early hypophosphatemia in critically ill children and the effect of parenteral nutrition: A secondary analysis of the PEPaNIC RCT, Impact of calorie intake and refeeding syndrome on the length of hospital stay of patients with malnutrition: a systematic review and meta-analysis, Psychiatric and medical comorbidities of eating disorders: findings from a rapid review of the literature, Evaluation of the ASPEN guidelines for refeeding syndrome among hospitalized patients receiving enteral nutrition: A retrospective cohort study, Refeeding Syndrome: A Critical Reality in Patients with Chronic Disease, Incidence and Impact of Refeeding Syndrome in an Internal Medicine and Gastroenterology Ward of an Italian Tertiary Referral Center: A Prospective Cohort Study, Short-chain fatty acids combined with intronic DNA methylation of.