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1 Research Center, Institut Universitaire de Gériatrie de Montréal, Canada.
2 Nutrition Department, Université de Montréal, Canada.
3 Faculty of Management, McGill University, Montréal, Canada.
4 Medicine Department, Université de Montréal, Canada.
Address correspondence to Laurette Dubé, Faculty of Management, McGill University, 1001 Sherbrooke West, Montreal, Québec, Canada H3A 1G5. E-mail: laurette.dube{at}mcgill.ca
| Abstract |
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Methods. 32 patients (21 women, 11 men; age range, 6592 years) were observed during repeated meals in a geriatric rehabilitation unit (for a total of 1477 meals). Perceived hunger, aversion, and contemporaneous subjective states were reported before each meal. Protein and energy consumption was calculated from plate leftovers. Clinical measures were obtained from participants' medical charts.
Results. The hungeraversion relationship had a low inverse correlation (p =.001), with each uniquely contributing to protein intake (positive and negative effects, respectively; all p <.05). Hunger was positively associated with the perception of physical health and with mood (all p =.001). Aversion was associated with pain (p =.001). Furthermore, aversionintake relationships were influenced by moderators, whereas hungerintake relationships remained constant.
Conclusions. From a clinical perspective, these results suggest that nutritional interventions aimed at bolstering hunger and curbing aversion may be necessary to ensure optimal food intake. Subgroups of patients who would particularly benefit from these interventions are suggested.
Our current research was based on the premise that, in the hospitalized elderly, a better understanding of how feelings of hunger and aversion are modulated at any meal, and how they operate in influencing food intake, could lead to the development of innovative nutritional care strategies. We had three specific objectives. The first objective was to study the relationship between hunger and aversion and their respective contribution to food intake. Because research shows that positive and negative affective responses generally are not correlated strongly with each other (18,19), and that motivational processes tied to approach and withdrawal tendencies have distinct neurologic substrates (20), we expected hunger and aversion to vary relatively independently and to contribute significantly to food intake at any given meal.
Our second objective was to acquire knowledge on the relationships between each drive and other contemporaneous facets of subjective experience preceding the meal, such as the perception of good physical health, positive mood, and pain. For instance, although research shows that feelings of hunger are tied to the experience of positive mood around mealtime (21), previous research on mood suggests that it is an unlikely correlate of aversion (22). In addition, controlling pain in elderly patients with terminal cancer, who often develop food aversions, successfully improves food intake (23). However, pain research suggests that such intervention would leave hunger unaffected (24). Thus, in this regard, we expected hunger and aversion to have distinct significant contemporaneous correlates.
Finally, we studied moderators of the relationships between drives and intakes to identify population segments in whom the two drives have the most powerful impact on patients' food intake. Such segments would particularly benefit from the careful tailoring of interventions to modulate both hunger and aversion to achieve optimal food intake. We expected driveintake relationships to be moderated by individual (age, sex, body mass index), psychological (cognitive deficits, feelings of depression), and clinical factors (appetite, nutritional status, functional independence, physical impairment, and use of multiple medications) (13,25,26). This expectation is also based on research showing that important contextual variations exist in the signaling value of drives and other visceral influences in guiding decision making and behavior (27).
| METHODS |
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Energy and protein intake.-- Food intake was determined from the visual estimation of plate leftovers using the Comstock scale (29,30). To reduce measurement error in the estimation of food intake, rigorous and systematic monitoring of portion sizes from standardized recipes was performed during the study period [see Paquet and colleagues (31) for details]. We translated the estimated intake portions into energy and protein intake using the NutriWatch Nutrient Analysis Program (version 6.1.5F Delphi, E. Warwick, Cornwall, PEI, 1997). We expressed each participant's meal energy and protein intake in terms of his or her meal-level nutritional needs. We calculated meal-level nutritional needs as the product of a participant's daily energy and protein requirements (Harris-Benedict x activity factor of 1.3) by the mean proportion of the participant's daily intake for the corresponding meal type (breakfast, lunch, dinner) during the observation period.
Moderators.-- We obtained patient-level measures of individual, psychological, and clinical measures from the patients' hospital charts.
Individual characteristics we considered included age, sex, and body mass index (kg/m2).
Psychological variables were cognitive status and degree of depressed feelings. Cognitive status was evaluated using the Mini-Mental State Examination (32), with a higher score (maximum, 30) indicating better cognitive ability. We used the Geriatric Depression Scale-15 to rate depression (33), with a higher score indicating more feelings of depression.
Clinical variables included self-reported appetite at admission, nutritional status, functional status, severity of impairment, and use of multiple medications. Appetite was dichotomized (1 = normal or good appetite; 0 = diminished appetite). We assessed nutritional status based on Thomas's Protein-Energy Malnutrition Index, which comprises body mass index, percentage of ideal body weight, triceps skinfold, midarm circumference, serum albumin, total lymphocyte count, and hemoglobin (34). We adapted the Protein-Energy Malnutrition Index so that a score of 3 or higher with both anthropometric and biochemical anomalies on this 7-point scale indicated severe malnutrition. We assessed functional independence using the Functional Independence Measure (35), with a higher score (maximum, 126) indicating greater independence. The geriatrician on the research team (M.J.K.) evaluated the severity of physical impairment from the participants' physical examination report using the Cumulative Illness Rating Scale (36), with a higher score (maximum, 52) indicating greater impairment. Finally, polypharmacy reflects the number of prescription drugs patients were taking at admission.
Statistical Analyses
We collected data for 1477 meals. We excluded participants for whom information for a variable was missing, or meals for which data were missing for a meal-level variable, from the analyses involving that particular variable.
Analyses performed to fulfill research objectives were of three kinds. First, we tested the distinctive contribution of hunger and aversion to intake using random coefficient analysis (37). This analysis estimated the ability of feelings of hunger and aversion reported before each meal to predict food intakes (energy and protein), taking into consideration both within-participants and between-participants variability. In random coefficient analyses, the proportion of variance in the dependent variables explained by the predictor is reflected in Schwarz's Bayesian Information Criterion (BIC) (38), with a higher value reflecting better fit. The contribution of each predictor is estimated in a distinct parameter (akin to beta in a regression analysis).
Second, we computed partial correlations between three sets of measures, that is, (a) between the two drives, hunger and aversion; (b) between each drive and other subjective contemporaneous states (physical health, mood, and pain); and (c) between each drive and intakes (energy and protein). We did this to control for response tendencies associated with repeated measurements so as to render all observations comparable. To achieve this, we determined correlations based on residual scores obtained from regression analyses in which each variable to be correlated was predicted by indicator variables created for all participants (39).
Third, to explore the moderating role that individual, psychological, and clinical factors may play on the relationships between drives and intakes, we calculated the same set of partial correlations (just described) separately for subgroups presenting low and high values of each moderator. The subgroup assignment was based on the variable's median value (except for sex and age, for which categories were predefined). We compared subgroup correlation coefficients using Fisher's Z transformation (40). All data were entered using Microsoft Excel 97 (Microsoft, Redmond, WA). We performed the analyses using SPSS 10.0.5 for Windows (SPSS, Chicago, IL). We performed the random coefficient analysis using the Proc Mixed procedure from SAS version 6.12 (SAS Institute, Cary, NC). In all analyses, we considered two-tailed probability values (p <.05) significant; however, because of the early stage of research, results with p <.10 are also presented.
| RESULTS |
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Contemporaneous Correlates of Hunger and Aversion
Analyses further revealed that the two drives presented distinct contemporaneous correlates. Namely, that hunger was directly related to the contemporaneous experience of perceiving oneself to be in good physical health (r = 0.21, p =.001) and in a good mood (r = 0.26, p =.001), with no statistical link with pain intensity (p >.90). In contrast, pain was the only correlate of aversion (r = 0.17, p =.001; the other two p values >.15).
Moderators
We considered moderators of drivesintake relationships to explore characteristics that could define subgroups that differed in terms of the strength of these associations (Figure 1). We analyzed each moderator separately.
Although the hungerintake relationships remained insensitive to all moderators (all p values >.19), those between aversion and intake varied by sex, cognitive status, appetite, nutritional status, degree of functional independence, and impairment severity (Table 2). More specifically, aversion was more strongly inversely related to both intakes in men, in participants with lower cognitive status, and in those with lower impairment. The more functionally independent participants showed a stronger aversionenergy relation, with directionally consistent results for protein intake. Furthermore, the aversionprotein relation was stronger in those with normal or good appetite and better nutritional status.
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| DISCUSSION |
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The finding that hunger and aversion were weakly correlated was consistent with previous research on other types of affective responses (18,19). This implies that interventions designed to improve hunger may have little effect on the prevention of aversion, and vice versa. Because both hunger and aversion contributed equally to food intake, it is important to envision interventions aimed specifically at each drive. Insights into appropriate strategies are provided by their distinct correlates.
Recall that hunger was tied to the contemporaneous state of good physical health and positive mood. Reliable evidence suggests that mood is sensitive to factors that can be built into the meal environment, such as music, aesthetic decor, and pleasant smell (41), and that such environmental manipulations do affect food intake in hospitalized geriatric patients (42), although the possible intermediary role of positive mood was not explored. We found no research that has tested strategies to improve perceptions of good physical health. However, comments from participants in the current study suggested that ensuring time to rest before the meal after the various activities and therapies that patients engage in between meals might contribute to improvements in this regard. This proposition would have to be tested in future research.
Turning to aversion, pain relief, through a more effective use of pain medication or simply using relaxation techniques, for example, could help curb feelings of aversion and their deleterious effects on food intake. This would be consistent with findings of the study in elderly patients with terminal cancer noted earlier (23). Furthermore, the aversionprotein intake relationship was particularly strong for elderly patients with good appetite and better nutritional status at admission, making them susceptible to potential onset of malnutrition during the course of hospitalization. In support of this idea, other research has noted that patients' feelings of aversion may arise in hospital settings where meals are eaten in the presence of other patients with feeding tubes or who exhibit inappropriate feeding behaviors (25). Thus, our results suggest that interventions designed to monitor and curb feelings of aversion by ensuring an appropriate social environment at mealtime, for example, may help to prevent malnutrition.
Finally, questions arise about the drives' effects being observed more strongly on protein intake compared with energy intake. These results may be tied to the fact that protein is particularly sensitive to mechanisms regulating short-term human feeding behavior (43), which may also make it especially sensitive to drives. In addition, our findings could also be tied to results of studies that have found animal protein to be a privileged target for learned food aversions in humans (44).
In the current study, we identified population segments for whom the careful tailoring of interventions to modulate hunger and aversion to improve food intake might be particularly beneficial. These segments included patients for whom aversion was most strongly associated with intakes (i.e., men, patients with light cognitive deficits, and those in relatively better clinical condition at admission, as indicated by normal appetite, good nutritional status, greater functional independence, and lower levels of impairment). Further quantitative studies are needed to test the existence of these segments in a larger population sample.
Conclusion
Our results underscore the need to enrich current nutrition practice in treating malnutrition in hospitalized geriatric patients with a more systematic consideration of interventions that aim to modulate hunger and aversion as an intrinsic part of nutritional care. Because drives are influenced by the quality of the immediate subjective experience (45), careful design of sensorial, environmental, and social components surrounding the meal are likely to improve food intake. Indeed, results from recent studies of the influence of specific interventions on food intake in elderly people are consistent with this notion (23,46). We hope that our findings will foster further practice and research development in this direction.
| Acknowledgments |
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Laurette Dubé is a Canadian Institute of Health Research/Social Sciences and Humanities Research Council of Canada career scientist.
Received March 17, 2003
Accepted August 11, 2003
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