Application Of Structural Equation Models In Medicine

Objective The medical model should be bio-psycho-social medical model, a large number of latent variables are involved in many medical scientific researches. The application of linear and nonlinear structural equation models in the occupational psychology and psychiatry had been explored in this paper. In order to describe developmental processes at both the inter- and intra-individual levels, latent growth model had been applied to analyze the longitudinal data. Consequently this paper had provided scientific method for the analysis of latent variable and longitudinal data in medicine.Methods Confirmatory factor analysis had been applied to evaluate the congeneric reliability and its 95% confidence interval, then the results had been compared with Cronbach's a coefficients. In view of many latent variables in occupational psychology, linear structural equation model had been utilized to explore the relationships between the occupational stress and work ability. However, models with interaction and nonlinear effects are often encountered in the social and behavioral sciences. For example, father's rearing styles and mother's rearing styles may have the interactive effects on the behavioral and emotional problems of adolescents, so the latent variable interaction modeling had been applied to test their relations. Latent growth model had been applied to the analysis of longitudinal data of clinical trial, and the result had been compared with that of analysis of variance forrepeated measurement.Results (1) The 95% confidence lower limits of congeneric reliability of occupational stress inventory were higher than 0.60. Cronbach's a coefficients were lower than the congeneric reliability indexes, but many of them were in the 95% confidence interval of congeneric reliability.(2) Role insufficiency, psychological strain, physical strain and vocational strain could influence self-rating work ability, physiological state and psychological state, each total effect of them was larger and negative. Rational/cognitive factor had positive effect on self-rating work ability, physiological state and psychological state. Furthermore, the social position directly influenced self-rating work ability, age and length of service had direct effect on physiological state. Else factors such as role ambiguity, physical environment, recreation and self-care had small influence to work ability, but people should attach importance to them.(3) There were interactive effects of father's rearing styles and mother's rearing styles on behavioral and emotional problems of adolescents, but the manners of influence were not the same for the different sex. For the male, father's warmth and understanding, overladen intervention, overprotection, mother's punishment, overladen intervention and protection, and interaction between father's overprotection and mother's overprotection were found to be related to the behavioral and emotional problems. But for the female, father's warmth and understanding, mother's warmth and understanding, overladen intervention and protection, and interaction between father's overladen intervention and mother's overladen intervention influenced the behavioral and emotional problems. In addition, other factors of rearing styles had effect on some factors of emotional problems. If father and mother simultaneously adopted the rearing styles of punishment, rejecting and denying, lack-of- warmth and understanding, the children were more likely to have problems.(4) The results of latent growth model and analysis of variance for repeated measurement both showed that there was no significant difference between the score of sleep dysfunction rating scale (SDRS) in two groups, but the scores of SDRS in different time points were statistically significant difference. Besides, latent growth model provided the developmental trajectory of SDRS score over times and indicated that instantaneous rate oftrue change after treatment was negatively associated with the initial level, but the curvature was positively associated with the initial level. This implied that those who had more serious sleep dysfunction were more likely to get better rapidly after treatment but there were more likelihood to rebound when completed treatment. Importantly, both the initial level and the change of SDRS score among the participants in two groups varied significantly across individuals.Conclusions The application of structural equation model in medicine had been illustrated at large in this paper. The reliability index evaluated with confirmatory factor analysis was more accurate, and this method could provide the 95% confidence interval of congeneric reliability. Linear structural equation model could detect the direct effect of the occupational stress on work ability, but also indirect effect. Nonlinear structural equation model indicated that the interactive effects of father's rearing styles and mother's rearing styles could influence the behavioral and emotional problems of adolescents. Compared to more traditional analysis of variance for repeated measurement, latent growth model appeared to be a much stronger analytic technique for studying growth over time.