Altered interoceptive awareness in anorexia nervosa: Effects of meal anticipation, consumption and bodily arousal

Abstract

Objective: Impaired interoceptive awareness (IA), the subjective perception of internal body sensations, has been proposed as a vulnerability or maintaining factor in anorexia nervosa (AN). We examined whether IA of heartbeat and breathing sensations was impaired in AN across a range of arousal levels, and whether it was influenced by meal anticipation and consumption.

Method: IA was assessed using randomized, double-blinded, bolus intravenous infusions of isoproterenol, a peripheral beta-adrenergic sympathetic agonist, and saline. Fifteen women with AN and 15 age-, and sex- matched healthy comparisons (HC) were evaluated before and after consumption of a 1,000 Calorie meal. During each infusion participants rated their moment-to-moment intensity of heartbeat and breathing sensations with a dial. To measure IA we evaluated interoceptive detection thresholds, retrospective ratings of palpitation and dyspnea intensity, and interoceptive accuracy via correlations between subjective dial ratings and observed heart rate responses.

Results: Contrary to prediction the AN group was more likely to report detection of interoceptive sensations across all conditions, an effect driven by false discriminations at low arousal levels. Concordant with prediction, meal anticipation was associated with intensified interoceptive sensations, particularly dyspnea. There were no differences in interoceptive accuracy.

Discussion: This represents the first demonstration of interoceptive prediction errors in AN. Although IA is unimpaired at high arousal levels in AN, prediction signals are abnormal at low arousal levels, especially during meal anticipation. Altered interoceptive prediction signaling during meal anticipation could contribute to phenotypes of high anxiety in AN or alternatively, might be explained by enhanced meal associated anxiety.

Keywords: anorexia nervosa; anxiety; arousal; autonomic; eating; heartbeat; interoception; interoceptive awareness; isoproterenol; respiration.

Figure 1. Interoceptive detection rates during bolus isoproterenol infusions, before and after consumption of a 1000 Calorie meal

The AN group demonstrated abnormal detection at low arousal levels, as evidenced by increased detection rates at the saline, 0.1 and 0.25 mcg doses (*p < .05). AN = anorexia nervosa. HC = healthy comparison.

Figure 2. Interoceptive symptom magnitude during bolus isoproterenol infusions, before and after consumption of a 1000 Calorie meal

Participants concurrently rated the overall intensity of heartbeat and breathing sensations by rotating a dial during infusions. Ratings were measured by summating the area under the curve (AUC) of dial ratings generated during each infusion. Participants also provided retrospective ratings of dyspnea and palpitation symptom intensity after each infusion. A. Pre meal and post meal cardiorespiratory intensity. A significant group x meal interaction was observed (**p < .01; see table 2). B. Pre meal and most meal dyspnea intensity. A significant group x meal interaction was observed (*p < .05) as well as a significant group effect (##p < .01; see table 2). C. Pre and post meal palpitation intensity. Figures represent group means. Error bars are SE. Axis markers for the 0.1, 0.25 and 0.75 mcg doses have been omitted to improve figure clarity. AN = anorexia nervosa. HC = healthy comparison.

Figure 3. Interoceptive accuracy during bolus isoproterenol infusions, before and after consumption of a 1000 Calorie meal

A. Pre meal and post meal zero order cross correlation between interoceptive dial rating and heart rate response. B. Pre and post meal maximum cross correlation between interoceptive dial rating and heart rate response. There were no significant between group differences in these measures, but there was a significant effect of meal on both zero and maximum cross correlation (*p < .05, ** p < .01; see table 2). Figures represent group means. Error bars are SE. Axis markers for the 0.1, 0.25 and 0.75 mcg doses have been omitted to improve figure clarity. AN = anorexia nervosa. HC = healthy comparison.