PubMed · 13507014
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G LINDGREN. 1957-11-29. [Alcohol & work].. https://pubmed.ncbi.nlm.nih.gov/13507014/
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This paper investigates generalized estimating equations for association parameters, which are frequently of interest in family studies, with emphasis on covariance estimation. Separate link functions are used to connect the mean, the scale, and the correlation to linear predictors involving possibly different sets of covariates, and separate estimating equations are proposed for the three sets of parameters. Simulations show that the robust 'sandwich' variance estimator and the jackknife variance estimator for the correlation parameters are generally close to the empirical variance for the sample size of 50 clusters. The results contradict Ziegler et al. and Kastner and Ziegler, where the 'sandwich' estimator obtained from the software MAREG was shown to be unsuitable for practical usage. The problem appears to arise because the MAREG variance estimator does not account for variability in estimation of the scale parameters, but may be valid with fixed scale. We also find that the formula for the approximate jackknife variance estimator in Ziegler et al. is deficient, resulting in systematic deviations from the fully iterated jackknife variance estimator. A general jackknife formula is provided and performs well in numerical studies. Data from a study on the genetics of alcoholism is used to illustrate the importance of reliable variance estimation in biomedical applications.
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OBJECTIVES: To determine whether caffeine (CA) clearance and salivary paraxanthine (PX)/CA ratio were altered in alcohol-dependent subjects and also whether salivary PX/CA ratio was affected by arylamine-N-acetylation 2 ( NAT-2) genotypes. METHODS: Of 30 male individuals recruited in assessing PX/CA ratio and CA clearance by ingestion of CA, 13 were healthy control, 10 were alcohol-dependent subjects with abnormal liver function tests and 7 were alcohol-dependent subjects with normal liver function. CA and PX levels were analysed by means of high-performance liquid chromatography. CA clearance was calculated from concentrations of CA in saliva at various time intervals. In another study, PX/CA ratios were assessed in 46 healthy male subjects. Their NAT2 status was genotyped using polymerase chain reaction with restriction fragment length polymorphism assay. RESULTS: Salivary CA clearance was well correlated with plasma and salivary PX/CA ratios in a wide range of the clearance. Correlation between salivary PX/CA ratio and CA clearance was considered high from the first hour after CA ingestion and continued so for at least 9 h (r=0.94-0.96, P<0.001). PX/CA ratio in saliva was also well correlated with plasma PX/CA ratio (r=0.98, P<0.001). Salivary CA clearance in the control group was significantly higher than that of patients with abnormal liver function tests, i.e. (mean+/-SEM; 95% confidence limits; l/h/kg) 0.094+/-0.013 (0.064-0.124) and 0.044+/-0.019 (0.002-0.091), respectively, and not different from that of patients with normal liver function tests [0.107+/-0.017 (0.066-0.149)]. Similarly, the same is true for PX/CA ratio. NAT2 genotype status did not apparently affect PX/CA ratio. CONCLUSION: Saliva-based PX/CA ratio was a convenient and robust method for assessment of CYP1A2 activity and liver function and it was shown to be altered in alcohol-dependent patients with mild abnormal liver function test.