Recent work on the social environment and psychological disorder has emphasized the multiple, bidirectional interactions between stressors, symptoms, and social support. However, even the few existing studies using prospective methods often have not adequately addressed important issues involving methodological and conceptual overlap of the parameters in the model. The current article presents one approach for isolating associations between life events, social support, and depressive symptoms. For a sample of married women who initially were relatively asymptomatic and reported nonconflicted marital relationships (n = 473), life events and social support were significant prospective predictors of depressive symptomatology (assessed 1 year later). In contrast, identical analyses performed on the full, unselected sample (N = 709) yielded discrepant, likely misleading, results. The theoretical relevance of these findings is discussed, along with the implications for the longitudinal study of dynamically interactive processes.Although research on the mental health implications of social support has become a topic of active empirical inquiry over the past decade, conceptualizations of the processes involved have expanded rapidly from simple models, involving one or two variables, to highly complex and interactive multivariate repre-

The association of occupational lead exposure with neuropsychiatric functioning was evaluated using data collected in 1982 in eastern Pennsylvania from 288 lead-exposed workers and 181 nonexposed subjects. Both current and cumulative exposure indices were used. After controlling for age, education, and income, few meaningful differences between exposed and control workers were found on either neuropsychologic or psychosocial variables. Dose-response analyses indicated that among lead-exposed workers, cumulative and current exposure were unrelated to neuropsychologic performance. The only meaningful associations occurred between exposure and level of conflict in interpersonal relationships. The results thus give evidence against hypotheses suggesting adverse neuropsychologic effects.

Recent community studies have suggested that low level lead exposure is significantly associated with blood pressure in the general population. This finding is inconsistent with the results of recent occupational studies of lead exposed workers, although the occupational studies contained serious methodological weaknesses. The present study examined the relation between occupational lead exposure and diastolic and systolic blood pressure in randomly selected samples of 270 exposed and 158 non-exposed workers. Four exposure indicators were examined: employment at a lead battery plant v a control plant, current blood lead value, current zinc protoporphyrin value, and time weighted average blood lead value. After controlling for other known risk factors such as age, education, income, cigarette usage, alcohol consumption, and exercise, the associations between exposure and blood pressure were small and non-significant. In the absence of a biologically feasible hypothesis regarding the mechanism by which low level lead exposure would influence blood pressure the present findings challenge the validity of the general population association.The relation between lead exposure and rises in blood pressure has recently received a great deal of attention because of the implication that mortality from cardiovascular and cerebrovascular disease might be reduced by lowering lead values in the environment.'1 Early reports focused on workers in the lead industries and described hypertension and nephritis as frequent manifestations of lead exposure.23 More recently, Dingwall-Fordyce and Lane showed an excess mortality from cerebrovascular disease in lead exposed workers with 25 years of exposure occurring before 1961.4 The excess mortality was greater for workers dying between 1926 and 1950 than for workers dying between 1951 and 1961. With one exception5 studies conducted since the classic research of Dingwall-Fordyce and Lane have confirmed the original findings.6-9 It should be noted that these studies were conducted in plants with extremely high levels of exposure to lead, and the study that failed to find an excess in mortality' was conducted after exposure had been substantially reduced. Because of these extremely high exposures and the almost inevitable nephrotoxicity, the most parsimonious explanation of the excess cardiovascular and cerebrovascular mortality is hypertension secondary to renal disease rather than primary hypertension.Two studies have directly examined the relation

Background Prone ventilation redistributes lung inflation along the gravitational axis; however, localized, nongravitational effects of body position are less well characterized. The authors hypothesize that positional inflation improvements follow both gravitational and nongravitational distributions. This study is a nonoverlapping reanalysis of previously published large animal data. Methods Five intubated, mechanically ventilated pigs were imaged before and after lung injury by tracheal injection of hydrochloric acid (2 ml/kg). Computed tomography scans were performed at 5 and 10 cm H2O positive end-expiratory pressure (PEEP) in both prone and supine positions. All paired prone–supine images were digitally aligned to each other. Each unit of lung tissue was assigned to three clusters (K-means) according to positional changes of its density and dimensions. The regional cluster distribution was analyzed. Units of tissue displaying lung recruitment were mapped. Results We characterized three tissue clusters on computed tomography: deflation (increased tissue density and contraction), limited response (stable density and volume), and reinflation (decreased density and expansion). The respective clusters occupied (mean ± SD including all studied conditions) 29.3 ± 12.9%, 47.6 ± 11.4%, and 23.1 ± 8.3% of total lung mass, with similar distributions before and after lung injury. Reinflation was slightly greater at higher PEEP after injury. Larger proportions of the reinflation cluster were contained in the dorsal versus ventral (86.4 ± 8.5% vs. 13.6 ± 8.5%, P < 0.001) and in the caudal versus cranial (63.4 ± 11.2% vs. 36.6 ± 11.2%, P < 0.001) regions of the lung. After injury, prone positioning recruited 64.5 ± 36.7 g of tissue (11.4 ± 6.7% of total lung mass) at lower PEEP, and 49.9 ± 12.9 g (8.9 ± 2.8% of total mass) at higher PEEP; more than 59.0% of this recruitment was caudal. Conclusions During mechanical ventilation, lung reinflation and recruitment by the prone positioning were primarily localized in the dorso-caudal lung. The local effects of positioning in this lung region may determine its clinical efficacy. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New