Skin and respiratory symptoms among workers with suspected work-related disease.

BACKGROUND: Many workers are exposed to chemicals that can cause both respiratory and skin responses. Although there has been much work on respiratory and skin outcomes individually, there are few published studies examining lung and skin outcomes together. AIMS: To identify predictors of reporting concurrent skin and respiratory symptoms in a clinical population. METHODS: Patients with possible work-related skin or respiratory disease were recruited. An interviewer- administered questionnaire collected data on skin and respiratory symptoms, health history, smoking habits, workplace characteristics and occupational exposures. Predictors of concurrent skin and respiratory symptoms were identified using multiple logistic regression models adjusted for age, sex and atopy. RESULTS: In total, 204 subjects participated; 46% of the subjects were female and the mean age was 45.4 years (SD = 10.5). Most subjects (n = 167, 82%) had possible work-related skin disease, compared with 37 (18%) subjects with possible work-related respiratory disease. Subjects with a history of eczema (OR 3.68, 95% CI 1.7-7.8), those from larger workplaces (OR 2.82, 95% CI 1.8-7.4) and those reporting respirator use at work (OR 2.44, 95% CI 1.2-4.8) had significantly greater odds of reporting both work-related skin and respiratory symptoms. Current smoking was also associated with reporting concurrent skin and respiratory symptoms (OR 2.57, 95% CI 1.2-5.8). CONCLUSIONS: Workers reported symptoms in both systems, and this may be under-recognised both in the workplace and the clinic. The association between history of eczema and concurrent skin and respiratory symptoms suggests a role for impaired barrier function but needs further investigation.

Developmental studies of alertness and encoding effects of stimulus repetition.

The findings reviewed here suggest a broadened view of the stimulus-familiarization effect as one of a general class of phenomena resulting from repetition-induced changes in the processes of alterness and encoding. Cantor's original observation of slowed responding to familiarized stimuli can be attributed on this account to experimental conditions under which the magnitude of alterness decrement is greater than encoding facilitation. Exactly the opposite result can be obtained by arranging conditions so as to highlight the encoding facilitation effect relative to the alterness decrement effect. For example, faster responding to familiarized stimuli has been found under conditions in which (1) the imperative stimulus is preceded by a neutral warning signal or, (2) a delay is imposed between the familiarization and the test phases. Earlier, it was noted that the experimental technique of repeated stimulus presentation is widely used in the study of infant perception, with little concern for the mechanisms responsible for what is generically referred to as habituation. Posner and Rothbart (1980) made a similar observation and suggested, on the basis of Kraut's (1976) results, that Habituation in the infant can be viewed as a reduction in the flow of information from the recognition pathway [encoding] into the alerting system. Input is still processed along the recognition pathway, but its failure to activate the alerting system reduces the availability of the central processor and hence of nonhabitual responses. We have developed a model of attention that accounts for our findings and embodies Posner and Rothbart's general idea. It suggests that both the alertness and the encoding functions must reach separate threshold levels for a correct recognition response. The time required to get to each threshold level is changed as a function of stimulus repetition. Repetition slows alertness "rise time," but it speeds encoding "rise time." In comparing the responses to a familiarized color versus those to a novel color, the model can be seen in Fig. 1a. Because any response must await an appropriate level of alertness, the familiarized stimulus is responded to more slowly than the novel one, even though encoding rise time to the familiarized stimulus if fast. Either a delay between familiarization and test or a warning signal acts to mitigate the effects of familiarization on alertness. Alertness rise time for the familiarized stimulus is similar to that for the novel stimulus, but encoding rise time for the familiarized stimulus is faster than for the novel.(ABSTRACT TRUNCATED AT 400 WORDS)

An alertness decrement hypothesis of response inhibition to repeatedly presented stimuli.

Both inhibitory and facilitative effects of repeated stimulus presentation have been observed. Two-factor theory attributes both kinds of effects to changes in specific components of attention. The theory claims that repeated exposure (a) decreases the alerting capacity of a stimulus and (b) facilitates encoding. The purpose of the present research was to provide further evidence that alertness decrement underlies the inhibitory effects of stimulus repetition. Adults were exposed to 30 presentations of a colored circle prior to performing a choice-reaction time (RT) task on which the targets were the familiarized stimulus and a novel stimulus. A warning signal occurred at one of three intervals prior to target onset. It was predicted from the literature on the temporal characteristics of alertness that the relative speed of responding to the familiarized stimulus would vary as a function of the warning signal-target interval. As predicted, responses to the familiarized stimulus were (a) slower than to the novel stimulus at intervals of 0 and 2,500 ms, but (b) faster than to the novel stimulus at 450 ms. The convergence of these findings with the alertness literature suggests an alertness decrement interpretation of response decrements to repeatedly presented stimuli.

Stimulus repetition effects on attention to words and colors.

Mere observation of 30 presentations of a colored form results in slower reaction time responses to the familiarized stimulus than to a comparable novel stimulus. Prior research suggest that this result is due to two subsidiary effects of repetition: alertness decrement and encoding facilitation. Four experiments were conducted to compare the effects of stimulus repetition on colors and words. The two-factor theory of repetition was found to hold for words as well as for colors; for words, in contrast to colors, encoding facilitation was found to be stronger than alertness decrement.

A two-factor theory of stimulus-repetition effects.

It is a well-documented finding that children respond more slowly to a stimulus that has been presented repeatedly just before test than to a novel stimulus. The effect, for which a two-factor theory has recently been proposed, did not occur in the only previous study of adults using a comparable procedure. Experiment 1 demonstrated the effect with adults. The previous negative finding may have been the result of too few repetitions of the stimulus. Experiment 2 provided additional support for the two-factor theory. The theory suggests that the effect is the net result of partially counteracting changes in two attentional processes. One process, the alertness elicited by a stimulus, is held to decrease as a result of repeated presentation of the stimulus, while the second process, encoding, is facilitated. The hypothesis tested in Experiment 2 was that the alertness decrement dissipates over a brief passage of time, while the facilitation of encoding does not. Subjects exposed to a repeatedly presented color were tested either immediately thereafter or after a 15-min or 30-min interval. As predicted, the observed effect shifted from one of flower response to one of faster response to the repeated stimulus as the delay interval increased.