Weighted Likelihood Estimation Method Based on the Multidimensional Nominal Response Model

The Monte Carlo study evaluates the relative accuracy of Warm＇s （1989） weighted likelihood estimate （WLE） compared to the maximum likelihood estimate （MLE） using the nominal response model. And the results indicate that WLE was more accurate than MLE.

Evaluation of latent links between irritable bowel syndrome and sleep quality

AIM:To examine the links between quality of sleep and the severity of intestinal symptoms in irritable bow-el syndrome(IBS).METHODS:One hundred and forty-two outpatients(110female,32 male)who met the Rome Ⅲ criteria for IBS with no psychiatric comorbidity were consecutively en-rolled in this study.Data on age,body mass index(BMI),and a set of life-habit variables were recorded,and IBS symptoms and sleep quality were evaluated using the questionnaires IBS Symptom Severity Score(IBS-SSS)and Pittsburgh Sleep Quality Index(PSQI).The associa-tion between severity of IBS and sleep disturbances was evaluated by comparing the global IBS-SSS and PSQI score(Pearson's correlation and Fisher's exact test)and then analyzing the individual items of the IBS-SSS and PSQI questionnaires by a unitary bowel-sleep model based on item response theory(IRT).RESULTS:IBS-SSS ranged from mild to severe(120-470).The global PSQI score ranged from 1 to 17(median 5),and 60 patients were found to be poor sleepers(PSQI>5).The correlation between the global IBS-SSS and PSQI score indicated a weak association(r=0.2 and 95% CI:-0.03 to 0.35,P<0.05),which becomes stronger using our unitary model.Indeed,the IBS and sleep disturbances severities,estimated as latent variables,resulted significantly high intra-subject cor-relation(posterior mean of r=0.45 and 95% CI:0.17 to 0.70,P<0.05).Moreover,the correlations between patient features(age,sex,BMI,daily coffee and alcohol intake)and IBS and sleep disturbances were also ana-lyzed through our unitary model.Age was a signif icant regressor,with patients≤50 years old showing more severe bowel disturbances(posterior mean=-0.38,P<0.05)and less severe sleep disturbances(posterior mean=0.49,P<0.05)than older patients.Higher daily coffee intake was correlated with a lower sever-ity of bowel disturbances(posterior mean=-0.31,P<0.05).Sex(female)and daily alcohol intake(modest)were correlated with less severe sleep disturbances.CONCLUSION:The unitary bowel-sleep model based on IRT revealed a strong positive correlation between the severity of IBS symptoms and sleep disturbances.