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S C Stenton

Publications and source records attributed to S C Stenton.

At least 19 recordsLinked to original sources
PubMed2002

Apparent but not real increase in asthma prevalence during the 1990s.

The authors investigated changes in asthma prevalence and perception of bronchoconstriction over 6 yrs in adults of Newcastle-upon-Tyne. Postal questionnaires were sent to 6,000 subjects aged 20-44 yrs in 1992-1993 and 1998-1999. Random samples of 600 responders had assessments of atopy, airway responsiveness, and their ability to perceive methacholine-induced bronchoconstriction. The prevalences of asthmatic symptoms, physician-diagnosis, and medication use increased by an average of 4.4%, particularly in subjects aged <30 yrs (8.7 versus 2.7). Atopy prevalence increased from 25% to 31% but atopics and nonatopics had similar mean changes in questionnaire data (5.2 versus 3.4). The probability of a positive methacholine test decreased as did the mean methacholine dose/response slope (0.00527 to 0.00379), indicating lower levels of airway responsiveness. This can be largely explained by an increase in use of inhaled corticosteroids (5.0-9.3%). The proportion of subjects perceiving bronchoconstriction during methacholine tests increased from 63 to 77%. The authors conclude that current changes in asthma epidemiology in adults may result from increased awareness of symptoms (and/or an increased willingness to report them), and from an increased willingness of physicians to make the diagnosis and prescribe treatment, not from increased disease prevalence.

Adolescent↗
PubMed2001

Asthmagenicity of coal mine roof-bolting resins: an assessment using inhalation provocation tests.

Inhalation provocation tests were used to assess whether the volatile products of an activated resin had caused occupational asthma in a non-random sample of six asthmatic coal miners. The resin system uses the polymerization of polyester and styrene under the influence of the cross-linking agent dibenzoyl peroxide to secure roof, wall and floor bolts in mine tunnels. The tests were conducted sequentially in a double-blind fashion over a 'dose' range which extended just beyond the maximum likely to have been experienced occupationally during a single day's work. The tests were monitored by symptoms, changes in the forced expiratory volume in 1 s (FEV1) and changes in airway responsiveness. All subjects completed the series of tests without any significant decrements in FEV1 or significant increases in airway responsiveness. We conclude that the use of this resin system is not likely to have been the cause of the asthma in the test subjects, nor in the larger group of miners of which they were a sample, but neither possibility is fully excluded and the participants may not have been adequately representative of other asthmatic coal miners.

Asthma↗
PubMed1998

Age-dependent inaccuracy of asthma death certification in Northern England, 1991-1992.

Asthma mortality appeared to increase two-fold in the UK from the mid- 1970s to the early 1990s, but there is evidence of inaccuracy in asthma death certification and so a region-wide investigation was undertaken to assess whether this recorded statistical trend might have been partly or wholly artefactual. A total of 35 respiratory physicians, distributed in panels of three, systemically reviewed the hospital and general practice records of 210 subjects with physician-diagnosed asthma who died in 1991 and 1992. The death certificates indicated that asthma was considered to be the primary cause of death in 103 (group 1), a contributory cause in 70 (group 2) and not relevant in 37 (group 3). There was agreement within the panels that 43% of the subjects had probably never suffered from asthma. Discordance between the panels and the certifying physicians over the correct death certification category was high for group 1 (45% for those aged <65 yrs, 75% for those aged > or =65 yrs and 64% overall) and group 2 (67%), but much less for group 3 (22%). This study concludes that asthma death certification provides a markedly inaccurate picture of asthma mortality, particularly in elderly subjects. Thus, it is speculated that if the magnitude of this source of inaccuracy has increased over the last two decades, the apparent recent increase in asthma mortality may be largely artefactual.

Aged↗
PubMed1998

Perception of respiratory symptoms after methacholine-induced bronchoconstriction in a general population.

In an epidemiological study, methacholine-induced bronchoconstriction was used as a physical illustration of the sensations associated with asthma. The objective of this study was to assess whether familiarity with these sensations could be used as a measure of asthma prevalence. Eight hundred and seventy six subjects aged 20-44 yrs completed a respiratory questionnaire and a measurement of airway responsiveness (the provocative dose of methacholine causing a 20% fall in forced expiratory volume in one second (PD20)). Subjects were asked about their perception of, familiarity with and description of the respiratory sensations experienced at the time of maximal bronchoconstriction. The questionnaire-derived lifetime prevalences of wheeze, chest tightness and undue breathlessness were 43, 35 and 22% respectively. Asthma medication was used by 8% and the lifetime prevalence of diagnosed asthma was 12%. Quantifiable levels of airway responsiveness were measured in 34%, and airway responsiveness in the range considered to be consistent with untreated active asthma was present in 21%. Bronchoconstriction was perceived by 59%. Perception of bronchoconstriction was associated with the magnitude of bronchoconstriction, younger age, female sex and questionnaire-reported symptoms. Of subjects able to perceive bronchoconstriction, 58% reported previous experience of (familiarity with) the associated respiratory sensations. Familiarity with the sensations of bronchoconstriction was associated with questionnaire-reported symptoms, diagnosed asthma and increasing levels of airway responsiveness. There was poor agreement between the respiratory symptoms reported by questionnaire before the methacholine test and the words used to describe respiratory sensations induced by the test. Familiarity with the sensations of methacholine-induced bronchoconstriction has all the appropriate associations of a measure of asthma prevalence and may be a useful adjunct to symptom questionnaires and airway responsiveness measurements in epidemiological studies. A sizeable number of subjects can be identified with intermediate levels of airway responsiveness, who are able to perceive bronchoconstriction and are familiar with the sensations associated with it, yet who are not recognized to suffer from asthma.

Adult↗
PubMed1997

Occupational asthma in an isothiazolinone manufacturing plant.

A chemical plant operator developed asthma five months after starting work in an isothiazolinone manufacturing plant. He described symptoms of late asthmatic reactions after work with isothiazolinone. Airway responsiveness to methacholine improved tenfold when he was removed from the plant for 18 days. A workplace challenge study then resulted in a deterioration in airway responsiveness to its earlier level and in progressive falls in forced expiratory volume in one second (FEV1) over three days at work compared with control days, indicating statistically significant late asthmatic reactions of increasing severity.

Anti-Infective Agents↗
PubMed1996

Occupational tuberculosis and a failed postgraduate medical examination.

A 40 year old pathologist presented with a tuberculous pleural effusion approximately one year after performing an autopsy as part of a postgraduate medical examination. She had made a diagnosis of disseminated tuberculosis but was told that this was incorrect and failed the examination. Bladder tissue from the cadaver was subsequently found to have grown M tuberculosis though none was cultured from lung tissue. No particular precautions against airborne infection were taken at the time of the autopsy and we speculate not only that the pathologist's original diagnosis was correct but that she became infected with M tuberculosis during the examination.

Adult↗
PubMed1996

Asthma, airways responsiveness and air pollution in two contrasting districts of northern England.

BACKGROUND: To assess the possible magnitude of differences between normal populations an epidemiological investigation of asthma was conducted in two strongly contrasting districts of northern England--rural West Cumbria on the west coast and urban Newcastle upon Tyne on the east coast. METHODS: A cross sectional survey of randomly identified men aged 20-44 years was conducted in two phases: phase 1, a postal survey of respiratory symptoms and asthma medication in 3000 men from each district; and phase 2, a clinical assessment of 300 men from each district comprising investigator administered questionnaires, skin prick tests, spirometry, and methacholine challenge tests. RESULTS: The phase 1 (but not phase 2) study showed a small excess of "ever wheezed" in Newcastle (44% versus 40%), but neither phase showed differences between the two districts for recent wheeze or for other symptoms characteristic of asthma. There were also no differences with regard to diagnosed asthma, current asthma medication, spirometric parameters, or airways responsiveness. The prevalence of quantifiable airways responsiveness (PD20 < or = 6400 micrograms) was 27.7% in West Cumbria and 28.2% in Newcastle. Regression analyses showed that PD20 was negatively associated with atopy and positively with forced expiratory volume in one second (FEV1); that an association between PD20 and current smoking could be explained by diminished FEV1; and that PD20 was not related to geographical site of residence. CONCLUSIONS: Neither airways responsiveness nor the other parameters of diagnostic relevance to asthma varied much between the two study populations, despite the apparent environmental differences. The most obvious of these were the levels of outdoor air pollution attributable to vehicle exhaust emissions, the ambient levels of which were 2-10 fold greater in Newcastle. Our findings consequently shed some doubt over the role of such pollution in perceived recent increases in asthma prevalence. It is possible, however, that an air pollution effect in Newcastle has been balanced by asthmagenic effects of other agents in West Cumbria.

Adult↗
PubMed1996

An epidemiologic investigation of asthma in welders.

To clarify whether asthma may be caused by fume from welding mild steel and to evaluate the possible strength of such an effect, we quantified airway responsiveness among young shipyard workers with different levels of fume exposure. Clinical investigation comprised a cross-sectional survey of 19- to 27-yr-old workers who were completing 3 to 9 yr of employment in various trades, and a control group of 15- to 17-yr-old school leavers who were applying for apprenticeships within the same trades. Both groups were subdivided into negligible-, ambient-, or high-exposure subgroups according to expected levels of fume exposure. Actual exposures were assessed in a parallel environmental survey. Participants were investigated by questionnaire, skin prick tests, spirometry, and methacholine tests. Complete data sets were obtained from 1,024 of the 1,070 eligible subjects (96%). Among the workers but not the school leaver controls, there was an increasing prevalence of positive methacholine tests across the exposure subgroups-negligible 37%, ambient 44%, high 49% (p < 0.05). Regression analyses showed that in males after allowing for the effects of atopy, current smoking, and age, the estimated geometric mean level of airway responsiveness of regular welders was twice that of workers with negligible exposure after 5 yr of work. This implies that fume exposure may have been critical in causing asthma in about 1% of the welders. A lesser effect (though not significantly so) was noted among the workers with ambient exposure.

Adult↗
PubMed1995

Asthmatic symptoms, airway responsiveness and recognition of bronchoconstriction.

During an epidemiological investigation of asthma in an occupational setting, 1126 subjects completed a modified Medical Research Council respiratory questionnaire, then underwent airway responsiveness measurements as PD20FEV1 to methacholine. Previous experience of bronchoconstriction was assessed in the 481 subjects with measurable airway responsiveness (PD20FEV1 < 6400 g) by asking 'have you ever felt like this before' at the end of their methacholine challenge tests, i.e. when the subjects were bronchoconstricted by FEV1 decrements of at least 20%. The responses to this question bore no relationship to the previously administered questionnaire responses about wheezing, chest tightness, coughing, or breathlessness. However, there was an inverse relationship with PD20FEV1 measurements (P < 0.001), the positive response rate to the question falling from 92% among those with PD20FEV1 < 50 micrograms to 27% among those with PD20FEV1 in the highest measurable range (3200-6400 micrograms). This suggests that airway responsiveness measurements are a more reliable guide to subjects' previous experience of substantial bronchoconstriction (i.e. asthma) than are the responses to respiratory questionnaires.

Adult↗
PubMed1995

Acute severe bronchoconstriction precipitated by coal tar bandages.

We report the occurrence of severe symptomatic bronchoconstriction in an atopic asthmatic subject following the application of coal tar bandages. Investigations showed that this was likely to have been caused by inhalation of coal tar vapour. We suggest that coal tar preparations should be used with caution in asthmatic subjects.

Acute Disease↗
PubMed1995

Effects of diurnal variation and prolonged refractoriness on repeated measurements of airways responsiveness to methacholine.

BACKGROUND: A number of studies have suggested that diurnal variation in airways responsiveness underlies the circadian rhythm of ventilatory function in asthma. Measurements of airways responsiveness are therefore often performed at standardised times in order to avoid this possible effect, but this is not practical for epidemiological studies. Refractoriness to methacholine has also been reported and this, too, could confound the results of methacholine tests repeated over short intervals. This investigation was carried out to evaluate the possible magnitude of diurnal variation and refractoriness in repeated measures of airways responsiveness to methacholine. METHODS: To investigate diurnal variation in airways responsiveness, 24 asthmatic subjects aged 18-45 underwent five methacholine tests over three days which were not necessarily consecutive: day 1 at 08:00 hours; day 2 at 08:00 hours, 14:00 hours, 20:00 hours; day 3 at 20:00 hours. To investigate refractoriness a retrospective analysis was undertaken of all paired methacholine tests performed in individuals within our unit between 1984 and 1990 where there had been no intervention likely to affect the results. RESULTS: The first investigation revealed no diurnal change in airways responsiveness although there was a change in FEV1. Mean PD20 did, however, increase 1.57 fold from 08:00 hours on day 1 to 08:00 hours on day 2 for subjects studied on consecutive days. The second investigation confirmed that a test interval of up to 24 hours (but not of 48 or more hours) was associated with a refractory index (PD20 test 2/PD20 test 1) of > 1. CONCLUSIONS: No diurnal variation in airways responsiveness was detected for measurements made between 08:00 hours and 20:00 hours, but an interval between successive tests of up to 24 hours was associated with refractoriness. Diurnal variation is not likely to exert an important confounding effect on methacholine tests carried out between 08:00 hours and 20:00 hours, but confounding could result from refractoriness if tests are repeated at intervals up to 24 hours.

Adult↗
PubMed1995

Effect of dietary sodium on airways responsiveness and its importance in the epidemiology of asthma: an evaluation in three areas of northern England.

BACKGROUND: Although several investigations have shown a relationship between asthma (or its surrogate, airways responsiveness) and dietary or urinary sodium, others have not, and the matter remains controversial. This "salt effect" has been investigated during two recent epidemiological surveys of men in northern England. The first assessed the possible effect on airways responsiveness of occupational exposure to welding fumes, and the second characterised airways responsiveness in two geographically distinct residential areas. Thus, three separate study areas/populations were involved. METHODS: Investigation 1 involved 1059 shipyard workers aged 16-27 years who were exposed variously to welding fumes, and Investigation 2 involved 587 men aged 20-44 years who lived in rural West Cumbria or in urban Newcastle upon Tyne. In Investigation 1, a 24 hour urine specimen was requested from each subject with quantifiable airways responsiveness (PD20 < or = 6400 micrograms methacholine) and from an equal number of subjects without measurable airways responsiveness from the same occupational subgroup. In Investigation 2, every subject was asked to provide a 24 hour urine specimen. RESULTS: Of the men undergoing methacholine tests, satisfactory 24 hour urine specimens were obtained from 234 (22.1%) in Investigation 1 and 232 (39.5%) in Investigation 2. Analysis using multiple linear regression, multiple linear logistic regression, and multiple regression for censored data produced consistent results within each study population but conflicting results between them, such that there was no hint of a relationship between airways responsiveness and 24 hour urinary sodium excretion in the shipyard workers of Investigation 1 nor in the rural West Cumbrian population of Investigation 2, but an association was found in the urban Newcastle population of Investigation 2. All study populations were sufficiently large to demonstrate anticipated relationships between airways responsiveness and atopy, baseline FEV1, and (Newcastle only) age. CONCLUSIONS: If airways responsiveness is related to dietary sodium the relationship is not likely to be strong.

Adolescent↗