Quality adjusted survival analysis: A neglected application of the quality of well-being scale

Abstract

Background In survival analysis, those who are alive are statistically coded as 1.0 while those who are dead are coded as 0.0. Since everyone who remains alive is given the same score, a person confined to bed with an irreversible coma is alive and is counted the same as someone who is active and asymtomatic. The Quality of Well-being (QWB) scale defines levels of wellness on the continuum between death and optimum function and integrates morbidity and mortality into the same number. This paper demonstrates the effect of including mortality in QWB estimates for male adults with HIV infection.

Method This study involves follow-up of a cohort of 386 male adults participating in the San Diego HIV Neurobehavioral Research Center (HNRC). Patients were evaluated using the QWB at enrollment and at six month intervals. All patients were classified into three stages of HIV disease according to the Center for Disease Control (CDC) classification: CDC IV (symptomatic HIV disease), CDC II or III (asymptomatic infection) and uninfected male controls.

Results QWB scores were calculated with and without mortality included for men in each CDC class who completed a one year (N = 148) or two year follow-up (N = 60). At each evaluation, there were significant differences among CDC classes and inclusion of deaths increased the variance accounted for by CDC class at each evaluation.

Conclusions HIV infection has significant impacts upon both morbidity and mortality. Survival analysis captures only the mortality dimension, while quality adjusted survival analysis using the QWB includes both dimensions. We propose quality adjusted survival analysis as a more sensitive method for assessing outcome in HIV disease and other health conditions.     

When Are Thought Experiments Poor Ones?

A characteristic of contemporary analytic philosophy is its ample use of thought experiments. We formulate two features that can lead one to suspect that a given thought experiment is a poor one. Although these features are especially in evidence within the philosophy of mind, they can, surprisingly enough, also be discerned in some celebrated scientific thought experiments. Yet in the latter case the consequences appear to be less disastrous. We conclude that the use of thought experiments is more successful in science than in philosophy. This revised version was published online in August 2006 with corrections to the Cover Date.     

Categories,subcategories, and the attenuation of proactive inhibition in free recall

In two experiments, “proactive inhibition” was observed in the free recall of a succession of 15-word lists. Recall performancc declined across lists when all lists were drawn from the same taxonomic category (e.g., occupations). But this decline did not appear when the successive lists were drawn from discrete subcategories (such as “professional” and “skilled manual” occupations). The findings clarify the conditions in which proactive inhibition effects in free recall are likely to occur. Specifically, when the set of items on any one list is more homogeneous than the set of items from all lists taken together, “proactive inhibition” will be attenuated.     

A stochastic model for rote serial learning

A model for the acquisition of responses in an anticipatory rote serial learning situation is presented. The model is developed in detail for the case of a long intertrial interval and employed to fit data where the list length is varied from 8 to 18 words. Application of the model to the case of a short intertrial interval is considered; some predictions are derived and checked against experimental data.The author wishes to thank Professors C. J. Burke and W. K. Estes for advice and assistance in carrying out this research.     

MATERNAL SELF‐REPORTED DEPRESSIVE SYMPTOMS AND MATERNAL CORTISOL LEVELS INTERACT TO PREDICT INFANT CORTISOL LEVELS

Three basic findings have emerged from research on maternal depressive symptoms and offspring hypothalamic–pituitary–adrenal functioning: (a) Mothers’ depressive symptoms are positively associated with their offsprings’ cortisol stress response, (b) numerous individual and interpersonal maternal characteristics moderate this association, and (c) maternal and infant cortisol levels are highly correlated. In combination, these findings have suggested that maternal cortisol levels may moderate the relation between maternal depressive symptoms and infant cortisol responsivity; the current study assessed this hypothesis. Participants were 297 mother–infant dyads who were recruited from the community. Maternal depressive symptoms were assessed via self‐report. Dyads participated in two differentially stressful infant challenges when infants were 16 and 17 months old. Mother and infant salivary cortisol was collected before and after challenges. Results indicate that maternal cortisol levels moderated associations between maternal depressive symptoms and infant cortisol levels across both challenges. Infants showed higher cortisol levels if their mothers had both higher depressive symptoms and higher cortisol levels, as compared to infants of mothers with higher depressive symptoms and lower cortisol, and to infants of mothers with lower depressive symptoms and either higher or lower cortisol levels. We discuss findings in relation to environmental and biological factors that may contribute to the intergenerational transmission of depressive symptoms.