Numbers of subjects having night-time wakening are shown.
* Values are the mean of three studies, and 95% CI, and p values 
in comparing “Before” and “After” shown.   NS = not significant.
** Signifcant decrease compared to number of Baseline study.

Values are the means of 40 subjects in each group, and 95% CI and P values in 
comparing “Baseline” and “Control film” or “Humorous Film” are shown. 
NS = not significant.
* Significant reduction compared to values of Baseline.

As shown in Table II, there was no difference of nocturnal salivary ghrelin levels at 23:00 h or at 00:50 h between healthy children and patients with AD at baseline (without viewing film). In contrast, nocturnal salivary ghrelin levels were significantly (P <0.01) elevated at 00:20 h in patients with AD in comparison with those at 23:00 h, while they were not elevated in healthy subjects at 02:00 h. Neither viewing control film nor humorous film had any effect on salivary ghrelin levels in healthy children at any time measured during the night. In contrast, viewing humorous film significantly reduced elevation of salivary ghrelin levels in AD patients at 02:00 h, while viewing control film failed to do so. This was not non-specific effect, since viewing humorous film had no effect on salivary ghrelin levels at 23:00 h or 05:00 h, and moreover, salivary amylase levels were not reduced at any time measured (Table III).

Values are the means of 40 subjects in each group, and 95% CI, and  P values in 
comparing “Baseline” and “Control film” or “Humorous film” are shown.  
NS = not significant.

We have demonstrated that salivary ghrelin levels at 02:00 h are elevated in AD patients compared to healthy children. This nocturnal elevation of salivary ghrelin may cause night-time wakening in AD patients, since viewing humorous film improved night-time wakening and reduced elevation of ghrelin levels. Although the effect of ghrelin on emotional responses remains to be elucidated, elevation of ghrelin levels were reported in sleep disturbance, anxiety and night-time wakening(3,4). Moreover, serum ghrelin levels were elevated in patients with epilepsy(12). Ghrelin injection in rats induces wakefulness(13). Stress increased ghrelin levels and patients with colicky pain had elevated serum ghrelin levels(6,7) Since AD patients are vulnerable to stress, it is tempting to speculate that chronic stress may elevate nocturnal salivary ghrelin levels, which in turn may cause night-time wakening(14).

It was reported that there was a inverse correlation between plasma ghrelin levels and IgE levels, in which plasma levels of ghrelin in allergic patients (AD or bronchial asthma) only at one point were measured(15). We have sequentially measured salivary ghrelin levels during night and found no difference of salivary ghrelin levels at baseline between healthy children and AD patients, except nocturnal elevation at 02:00 h in AD patients. More detailed study should be carried out to elucidate the relationship of ghrelin in allergic diseases.

We also demonstrated that viewing humorous film reduced elevation of nocturnal salivary ghrelin and improved night-time wakening in AD patients. This is not surprising. We have previously reported that viewing humorous film counteracts (i) stress-induced enhancement of allergic responses and neurotrophin production in AD patients, (ii) allergen-induced IgE production, and (iii) bronchial responsiveness to methacholine or allergen in patients with bronchial asthma(5,16,17). It is possible that relaxation caused by viewing humorous film may reduce elevation of nocturnal salivary ghrelin levels, which in turn may improve night-time wakening. Study is currently in progress to elucidate the mechanisms.

Nocturnal ghrelin secretion were higher in female adults compared to those in male adults (11). Thus, we also measured nocturnal ghrelin levels in female healthy children without night-time wakening or female AD patients with night-time wakening. Salivary ghrelin levels (mean [95% CI] fmol/mL) at 02:00 h in baseline study in female healthy children (n = 40, mean age 5 years) and female moderate AD patients (n = 40, mean age 5 years) were 32.4 [28.3-36.5] and 46.5 [41.2-51.8], respectively, which were higher than those in male children. After viewing humorous film, night-time wakening was improved in 37 AD patients out of 40, while night-time wakening was not improved in any AD patients after viewing control film. Moreover, salivary ghrelin levels in female healthy children were not reduced after viewing control film or humorous film: salivary ghrelin levels after viewing control film and humorous film were 33.4 [29.1-37.7] and 32.9 [29.0-36.8], respectively. In contrast, viewing humorous film significantly reduced salivary ghrelin levels in female AD patients, while viewing control film failed to do so: salivary ghrelin levels in female AD patients after viewing control film and humorous film were 47.4 [41.9-52.9] and 33.6 [29.1-38.1] (P<0.01) compared to 46.5 [41.2-51.8] at 02:00 h in baseline as above), respectively.

Collectively, it would be tempting to speculate that ghrelin may be involved in stress responses, and alleviation of stress by viewing humorous film may improve nocturnal elevation of ghrein production and night-time wakening in AD patients. Measure-ment of salivary ghrelin levels is non-invasive and useful in the study of ghrelin production, and viewing humorous film may be useful in the treatment of night-time wakening in AD patients.