Relationship of food allergy with quality of life and sleep in psychiatric patients

概要

（Purpose）
　It has been previously observed that food allergy (FA) is associated with depression and stress symptoms. However, few studies have thus far examined the relationship between FA and psychiatric disorders. We aimed to examine the possible relationship of FA with quality of life (QOL) and sleep in adult patients with psychiatric disorders.

（Methods）
　Subjects were 812 psychiatric patients (451 females, mean age: 42.7 ± 11.3 years) consisting of 430 patients with schizophrenia/schizoaffective disorder, 106 with depression, 124 with bipolar disorder, 40 with anxiety disorders, 38 with developmental disorders, 11 with eating disorders, and other 63 cases. We obtained information on FA and sleep disturbance via questionnaire. QOL was assessed with the MOS 8-Item Short-Form Health Survey (SF-8 Japanese version).

（Results）
　There were 126 patients (15.5%) who reported FA. SF-8 Physical component summary (PCS) and Mental component summary (MCS) scores were both significantly lower among individuals with FA than those without (p=0.001 and p=0.032, respectively). Also, PCS and MCS scores were found to decrease as the number of allergens increased (p=0.006 and p=0.043). Patients with sleep disturbance were common at 76.0% of the total. The proportion of people with sleep disturbance and that of nocturnal awakening were significantly higher in the group with FA than the group without (p=0.036, p=0.011). Additionally, the higher the number of allergens, the higher the proportions of people with sleep disturbance and nocturnal awakening (p=0.069, p=0.053).

（Discussion）
　In this study, for the first time, we have clarified the relationship of FA with QOL and sleep disturbance in a large sample of patients with psychiatric disorders. The mechanism of the relationship between food allergy and psychiatric disorders remains elusive, however, the following mechanisms are thought to be involved. When a food allergen enters the body, the allergen binds to the specific IgE antibody on the mast cells and activates the mast cells. Activated mast cells produce Th2 cytokines such as interleukin-4 (IL-4), IL-5 and IL-13, and chemokines, which induces inflammation by inflammatory cells, mainly eosinophils. In addition, a growing body of research suggests that mast cells play a crucial role in the pathogenesis of inflammation in central nervous system disorders. Zhou et al found that both ovalbumin (allergen)-specific IgG1 and ovalbumin-specific IgG2a in the cerebral cortex of food allergic mice were significantly increased compared to control mice. It is speculated that the increase in ovalbumin-specific IgG is due to entry into the brain via the blood-brain barrier (BBB) or the entry of peripheral IgG-secreting cells into the brain. The chymase level of the mast cell activation marker in the cerebral cortex of food allergic mice was also significantly increased compared to control mice. It was thus suggested that FA may cause an increase in allergic factors not only in peripheral organs but also in the brain. Furthermore, the number of total microglia and the ratio of activated microglia in both the cerebral cortex and the hippocampal CA1 region were also significantly increased in food-allergic mice, and the level of a proinflammatory cytokine Tumor Necrosis Factor-α (TNF-α) was increased. It is currently believed that activation of microglia releases inflammatory cytokines such as TNF-α and IL-6, causing an inflammatory response and exacerbating psychiatric disorders such as depression, schizophrenia, and autism. These mechanisms may underlie our findings that PCS, MCS were significantly lower in the FA group than in the non-FA group. To our knowledge, no research has been conducted on the mechanisms of FA and sleep disorders. Further basic and clinical research on this relationship is warranted.

（Conclusion）
　The results of this study indicate that FAs may reduce quality of life, especially sleep quality, in patients with psychiatric disorders. This suggests that for patients with mental illness, inquiring about their history of food allergies and allergens and avoiding exposure to these foods as much as possible in their diet may improve their quality of life and sleep. Further research is needed to clarify the mechanism by which food allergy is a risk factor for poor quality of life and sleep disorders.