Background
Survival for most end stage renal disease patients in Malaysia is by means of maintenance haemodialysis (HD). As of December 2013, there were 28,822 patients undergoing maintenance HD in Malaysia which represents a 3-fold exponential increase over the past decade [
1]. Annual figures from the Malaysian Dialysis and Transplant Registry cite malnutrition as a major problem as indicated by ~60 % of the HD population having serum albumin concentrations ≤40 g/L and body mass index (BMI) ≤25 kg/m
2 [
2]. These figures have persisted since 2002 [
2]. Unfortunately, although poor oral intake in these patients is the likely major factor contributing to malnutrition, the lack of dietician access to probe this issue prevails in most dialysis centres in Malaysia [
3].
Diminished appetite is often implicated in the chronology of protein-energy malnutrition which is prevalent in 30 to 75 % of the HD population [
4]. However, the emerging complex face of malnutrition today is protein energy wasting (PEW) syndrome and poor oral intake is hypothesized as one of the contributory factors. PEW patients commonly experience multiple nutritional and catabolic alterations that encompass persistent inflammation, acidosis and a state of hyper-metabolism leading to catabolism of muscle and fat [
5]. These are facets that are also common to anorexia and cachexia aetiology in chronic disease [
6]. Thus, assessment of under-nutrition remains problematical in PEW patients because of underreporting of diet records and the lack of trained dietary skills to quantify energy and protein intake [
5]. Expert opinion suggests that appetite assessment may serve as a diagnostic tool for PEW in dialysis patients [
7].
No studies to date have explored the link between appetite and PEW. Appetite assessment in HD populations were carried out using the single question pertaining to appetite from the 44-item Appetite and Diet Assessment Tool (ADAT), originally developed by the Haemodialysis Study Group [
8]. Studies have used this single question to correlate appetite with nutritional status of HD populations in different regions such as United States [
8,
9], Italy [
6] and Australia [
10]. Responses to this question-
During the past one week, how would you rate your appetite? are ranked according to 5 ratings, inclusive of
very good, good, fair, poor and
very poor. In a study comparing dietary intakes on dialysis and non-dialysis days, researchers concluded that appetite assessment using this 5-scaled question enabled detection of patients who had poor appetite requiring early intervention [
9]. Bossola et al. [
6] using the same appetite question found that appetite may fluctuate over time that could be associated with older age, more co-morbidities and frequent hospitalizations.
Since appetite assessment is widely accepted as an early warning of impending morbidity and nutritional concerns [
11,
12], we were interested in examining the relationship between the appetite question with the nutritional status and diagnosis of PEW in a Malaysian HD population. A recently expressed concern was the need to understand socioeconomic factors mediating cultural and environmental determinants of health outcomes in the chronic kidney disease population [
13]. In this context, it would be interesting to see if socio-cultural and multi-ethnic differences in these patients would affect the usability of this self-reported appetite rating. We hypothesize that self-reported appetite if correlated to markers of nutritional status, will also correlate with PEW diagnosis in the Malaysian HD population.
Discussion
Studies have validated the first question from ADAT to assess appetite in dialysis patients, associating poorer appetite to poorer QoL, malnutrition, inflammatory markers, morbidity, increased hospitalization and increased mortality [
6,
10,
12,
35]. When our patients were assessed using the 4-scaled appetite rating, only those with the poorer appetite ratings had significantly higher hsCRP and lower dry weight, BMI, MAC, MAMC, MAMA, LTM, serum urea and creatinine, dietary energy and protein intakes as well as SF-36 total scores. These findings were consistent with other studies [
4,
10‐
12]. Patients reporting
very good and
good appetite had weight-adjusted energy and protein intakes below the recommendations of KDOQI Nutrition Guidelines that is 25 kcal/kg ideal body weight for energy intake and 1.2 g/kg ideal body weight for protein intake. These findings concur with the opinion that suboptimal nutritional intake is a phenomenon in the dialysis population [
4,
37,
38]. Nutritional screening tools like DMS and MIS were found to correlate well with appetite assessment. However, we should note that this relationship is expected as appetite assessment is included as a component in these tools [
12]. In contrast with other studies [
4,
11,
38], serum albumin levels could not differentiate across appetite ratings for our HD patients. Altered serum albumin levels in chronic HD patients may be due to poor dietary intake, but most often metabolic acidosis and chronic inflammation may suppress albumin synthesis to a greater extent [
39].
Diminished appetite is hypothesized to be related to PEW [
6]. Logical thinking is that poor oral intake due to poor appetite would lead to malnutrition. Patients with prolonged poor appetite progressively develop malnutrition, invariably characterized by depleted muscle mass [
40]. Malnutrition along with an increased resting energy expenditure, inflammation and metabolic acidosis, that are coexistent in chronic kidney disease, may contribute to the aetiology of PEW [
5]. To the best of our knowledge, this study is the first to examine if subjective appetite reporting correlated to PEW prevalence in HD patients. We observed an increased trend in the percentage of PEW prevalence with poorer appetite ratings but owing to too few patient numbers reporting ‘poor’ appetite, a larger patient population is warranted to test this observation. After dichotomization, PEW prevalence was similarly distributed in both diminished and normal appetite categories. However, the adjusted odds ratio for the dichotomized appetite indicated that there was a marginal positive association between diminished appetite and PEW diagnosis. We found patients with diminished appetite were more likely to have lower LTM, serum urea and creatinine, nutritional status and QoL scores. This suggests that these markers were more indicative of poor oral intake. We believe that there is a possibility for genuine manifestations of anorexia-cachexia in our patients. Indeed, Bossola et al. [
6] have reported anorexia to be present in one-third of dialysis patients. Kalantar-Zadeh et al. [
12] reported anorexia to be present in 7 % of patients with “poor” appetite and 31 % in “fair” appetite categories.
Across the 4-scaled appetite ratings, our patients reported poor energy and protein intakes, as evident by the low EI: BMR ratio (<1.2). Resting energy expenditure has been noted to be different in PEW and non-PEW patients [
41]. This observation suggests that PEW patients have elevated resting energy expenditure with decreased feeling of hunger whereas non-PEW patients with normal resting energy expenditure may experience a feeling of hunger [
5]. Adaptive reduction in thermogenesis and feeling of hunger may have taken place in PEW patients in our study with prolonged diminished dietary intake, causing them to have a perception that their appetite was “normal”. Alternately, there were PEW patients who had acutely reduced food intake and were thus likely to report “diminished” appetite. Both these PEW groups could not experience hunger and thus fulfil model B as hypothesized by Carrero et al. [
5]. There is likelihood that PEW patients who report normal appetite require intervention because they have developed mechanisms in adaptive thermogenesis and hunger feeling [
5]. This may have masked the relationship of appetite as a reliable indicator of PEW in this patient population and would be regarded as a limitation to appetite assessment.
Studies report that diminished appetite is significantly associated with increased levels of inflammatory markers [
4,
11,
12]. However, we did not find this association between dichotomized appetite categories and hsCRP levels. This could be explained by patients reporting ‘poor’ appetite also experiencing severe inflammation. This is evident by their hsCRP levels being 5 times higher compared to those who reported better appetite. It was observed that patients reporting better appetite ratings had uniformly similar levels of hsCRP. This perhaps explains why we could not establish appetite as a connective factor between PEW and inflammation, although inflammation has been suggested as contributory to PEW [
5,
12].
Interestingly in the present study, we found that income was significantly associated with appetite ratings. The impact of culture on perceived health status should not be underestimated. Indeed, Angel and Thoits [
42] have suggested that the
experience of illness is subjective and culture bound and therefore cognitive and linguistic categories of illness would be constrained in terms of interpretative and behavioral options in response to symptoms of illness. Further, sick Malaysians are culturally ingrained to disclaim hunger or inability to eat or are even silent about the severity of illness. Behaviours contrary to these beliefs would be deemed impolite in a social structure without extensive medical insurance coverage or state health subsidies to cover medical health costs [
3]. In these families, the burden of paying health bills, related to dialysis care, falls on the remaining earning household members. We found that patients reporting diminished appetite were 5.75 times more likely to have poorer mental scores for SF-36, which is likely caused by increased anxiety or depressive symptoms and emotional concerns [
43,
44]. Ikizler et al. [
45] recognize that a poor socioeconomic situation may be implicated in the matrix of inadequate nutrient intake and depression.
In line with literature, we found that appetite assessment correlated well with markers of nutritional status in this HD population. Given that appetite assessment has been proposed as a potential diagnostic tool for PEW by the ISRNM [
7], we did observe a marginal positive association between diminished appetite and PEW. Therefore, this simple appetite question remains clinically relevant and may provide insights into poor oral intake in HD patients, serving as an early warning of impending malnutrition for nursing application where dieticians’ services are limited. Our study findings indicate that other potential diagnostic markers of PEW may lend greater evidence to linking appetite to PEW. Further research to elucidate PEW diagnostic criteria related to appetite assessment is warranted.
As this was a cross-sectional study, appetite assessment was only carried out once and we cannot elucidate the cause-and-effect between appetite and development and/or progression of PEW. We recommend that in order to have a more reliable understanding on appetite, the appetite assessment should be repeated over time. Furthermore, as this study only included patients from urban dialysis centres, we may not be able to extrapolate these observations to patients from rural dialysis centres.
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Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
SS, CHS, SHN, GSH performed data acquisition; SS, CHS, SHN, TK interpreted data, statistical analysis and wrote the manuscript; GSH, WSSC, GBL, HAG, SB, GA contributed to manuscript revision; SS, TK designed the study. All authors have read and approved the final version of the manuscript.