The objective of this study was to examine the experience of spouses caregiving for their spouse with Parkinson's disease (PD) and to determine whether their experiences differed by stage of disease. By using a cross-sectional design and mail questionnaire data from 380 spouse caregivers across 23 sites of the Parkinson Study Group, key caregiver variables were examined by stage of PD. Three categories of variables--caregiver role strain (10 measures), caregiver situation (four measures), and caregiver characteristics (four measures)--were analyzed by using t tests with Bonferroni correction. Specific types and amounts of role strain accumulated as the disease progressed, and they differed significantly between stages (p < 0.05). In the caregiving situation, the mean number of caregiving tasks tripled by stage 4/5. Negative changes in lifestyle plus decreases in predictability in caregivers' lives increased significantly in late-stage disease (p < 0.05). Caregiver characteristics of physical health and preparedness did not significantly differ across stages of disease. Depression was significantly higher by stage 4/5. Mutuality, the positive quality of the relationship as perceived by the caregiving spouse, declined beginning at stage 2. Caregiver strain is experienced across all stages of PD and accumulates significantly as the disease progresses. This study defines types and amounts of strain by stage of disease, which will be helpful in designing formal intervention trials to provide more effective help for spouse caregivers.

Metals are an important and emerging class of carcinogens. At least three metals, specifically nickel, chromium, and arsenic, are confirmed human carcinogens, and several more are suspected to have carcinogenic potential in man. Considering that the list of known human carcinogens of any type is very small, it becomes clear that metals make up a substantial portion of the list. Furthermore, many metals are very potent carcinogens in laboratory animals. Despite this, relatively little attention has been given to the topic of metal carcinogenesis. The reasons for this relative lack of attention are not clear but perhaps are fostered by a perception that, because metals are the simplest of molecules, their mechanism of action must also be simple. This could not be farther from the truth and, although no clear mechanisms have emerged in the area of metal carcinogenesis, it has become apparent that they are anything but simple. Metal carcinogens possess several unique characteristics including a remarkable target site specificity. Detection of the mechanism, or mechanisms, of metal carcinogenesis has, however, proven elusive, in part because of a wide diversity of metallic carcinogenic agents and the intricate nature of metal interactions in biologic systems. The following review explores this broad topic, with special emphasis on toxicological principles including dose-response relationships and potential mechanisms, using cadmium as an example.

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