Catherine Linaker

Personal exposure to nitrogen dioxide (NO2) and the severity of virus-induced asthma in children

n Summaryn n Backgroundn A link between exposure to the air pollutant nitrogen dioxide (NO2) and respiratory disease has been suggested. Viral infections are the major cause of asthma exacerbations. We aimed to assess whether there is a relation between NO2 exposure and the severity of asthma exacerbations caused by proven respiratory viral infections in children.n n n Methodsn A cohort of 114 asthmatic children aged between 8 and 11 years recorded daily upper and lower respiratory-tract symptoms, peak expiratory flow (PEF), and measured personal NO2 exposures every week for up to 13 months. We took nasal aspirates during reported episodes of upper respiratory-tract illness and tested for infection by common respiratory viruses and atypical bacteria with RT-PCR assays. We used generalised estimating equations to assess the relation between low (<7·5 μg/m3), medium (7·5–14 μg/m3), and high (>14 μg/m3) tertiles of NO2 exposure in the week before or after upper respiratory-tract infection and the severity of asthma exacerbation in the week after the start of an infection.n n n Findingsn One or more viruses were detected in 78% of reported infection episodes, and the medians of NO2 exposure were 5 (IQR 3·6–6·3), 10 (8·7–12·0), and 21 μg/m3 (16·8–42·9) for low, medium, and high tertiles, respectively. There were significant increases in the severity of lower respiratory-tract symptom scores across the three tertiles (0·6 for all viruses [p=0·05] and >2 for respiratory syncytial virus [p=0·01]) and a reduction in PEF of more than 12 L/min for picornavirus (p=0·04) for high compared with low NO2 exposure before the start of the virus-induced exacerbation.n n n Interpretationn High exposure to NO2 in the week before the start of a respiratory viral infection, and at levels within current air quality standards, is associated with an increase in the severity of a resulting asthma exacerbation.n n

Personal exposure to nitrogen dioxide and risk of airflow obstruction in asthmatic children with upper respiratory infection

BACKGROUND Several studies have linked air pollution by nitrogen dioxide (NO2) with increased hospital admissions for asthma in children. Exacerbations of asthma in children are often precipitated by upper respiratory infections. It is therefore possible that NO2increases the risk of airways obstruction when asthmatic children develop upper respiratory infections. METHODS To test this hypothesis a sample of 114 asthmatic children aged 7–12 years were followed for a total of up to 13 months. Probable upper respiratory infections were identified by consensus review of daily symptom diaries, and episodes of airways obstruction from serial records of peak expiratory flow (PEF). Personal exposures to NO2 were measured with Palmes tubes that were changed weekly. Generalised estimating equations were used to assess the relative risk (RR) of an asthmatic exacerbation starting within seven days of an upper respiratory infection according to estimated NO2 exposure during the one week period from two days before to four days after the onset of the infection. RESULTS The children were followed for an average of 34 weeks during which 318 upper respiratory infections and 224 episodes of reduced PEF were diagnosed. PEF episodes were much more likely to occur in the seven days following the onset of an upper respiratory infection than at other times. Estimated exposures to NO2 at the time of infections were generally low (geometric mean 10.6u2009μg/m3). Compared with exposures of ⩽8u2009μg/m3, exposures of >28u2009μg/m3 were associated with a RR of 1.9 (95% confidence interval 1.1 to 3.4) for the development of an asthmatic episode within seven days of an infection. CONCLUSIONS The findings give some support to the hypothesis that NO2increases the risk of asthmatic exacerbations following respiratory infections, even at relatively low levels of exposure. Further studies in populations with higher exposures would be useful.

Reliability of the Southampton examination schedule for the diagnosis of upper limb disorders in the general population

Background: Epidemiological research in the field of soft tissue neck and upper limb disorders has been hampered by the lack of an agreed system of diagnostic classification. In 1997, a United Kingdom workshop agreed consensus definitions for nine of these conditions. From these criteria, an examination schedule was developed and validated in a hospital setting. Objective: To investigate the reliability of this schedule in the general population. Methods: Ninety seven adults of working age reporting recent neck or upper limb symptoms were invited to attend for clinical examination consisting of inspection and palpation of the upper limbs, measurement of active and passive ranges of motion, and clinical provocation tests. A doctor and a trained research nurse examined each patient separately, in random order and blinded to each others findings. Results: Between observer repeatability of the schedule was generally good, with a median κ coefficient of 0.66 (range 0.21 to 0.93) for each of the specific diagnoses considered. Conclusion: As expected, the repeatability of tests is poorer in the general population than in the hospital clinic, but the Southampton examination schedule is sufficiently reproducible for epidemiological research in the general population.

Distribution and determinants of personal exposure to nitrogen dioxide in school children.

OBJECTIVES: To assess the distribution of personal exposures to nitrogen dioxide (NO2) in school children, and to investigate factors that might influence personal exposure. METHODS: NO2 exposures were assessed by use of passive diffusion tubes for 46 children aged 9-11 years, selected from two Southampton schools. The tubes were worn for seven days, and parallel measurements were made with static samplers in the childs kitchen, living room, classroom, and playground. Information about potential exposures was collected by questionnaire. RESULTS: Personal exposures to NO2, averaged over seven days, ranged from 11 to 257 micrograms/m3 (6 to 137 ppb) with a geometric mean of 36 micrograms/m3 (19 ppb). Exposures correlated with concentrations of NO2 recorded in the home, but the relation was far from exact. Factors associated with increased personal exposure included the use of gas appliances in the home, living with one or more smokers, and travel to school by means other than a car. However, together these variables only explained a small part of the variation in personal exposures. CONCLUSIONS: These findings reinforce the need for personal monitoring of exposure in studies investigating potential health effects of NO2 in children.

Does knee pain in the community behave like a regional pain syndrome? Prospective cohort study of incidence and persistence

Objectives: To investigate whether knee pain in the community behaves like a regional pain syndrome, determined by its association with mental health, self-rated health (SRH) and beliefs about prognosis. Methods: An 18-month postal follow-up was conducted in 1798 working-aged subjects, sampled from the community. At baseline questions were asked about pain in the knee lasting ⩾1 day in the previous 12 months, mental health (Short-Form 36), somatising tendency (elements of the Brief Symptom Inventory), SRH and concern about 12-month prognosis. At follow-up we asked about knee pain during the last 4 weeks, and whether it had been present for ⩾14 days or prescription-treated. Associations with incidence and persistence were explored using logistic regression. Results: The 1256 participants (70% response) comprised 468 with knee pain at baseline and 788 without. Among the former, 49% had persistent knee pain at follow-up, while among the latter, 15% reported new symptoms. Incident prescription-treated knee pain was strongly associated with all of the mental health variables and with SRH. The odds of knee pain persisting were significantly raised in the least versus most favourable bands of somatising tendency and SRH, and persistence was also significantly more common among those who at baseline were concerned that they would still have a problem in 12 months. Conclusions: Our observations support the hypothesis that knee pain in the community shares risk factors in common with other non-specific regional pain syndromes.

Personal exposures of children to nitrogen dioxide relative to concentrations in outdoor air

OBJECTIVES To investigate the relation between fluctuations in personal exposure to nitrogen dioxide (NO2) in school children and changes in outdoor NO2 concentrations. METHODS 114 Asthmatic school children aged 7–12 years were recruited from the Southampton area. Weekly average personal exposures to NO2 were measured over a 13 month period with passive diffusion tubes. At the same time, outdoor NO2 concentrations were monitored at a fixed site in the centre of Southampton. Correlations between weekly personal exposures and mean outdoor concentrations during the same periods were examined. RESULTS Mean duration of follow up was 32 weeks. Measurements of weekly mean personal NO2 exposures were generally low and ranged from 0.7 to 496 μg/m3 with a geometric mean of 17 μg/m3. Substantial variation in personal exposures occurred between children and more especially within individual children from week to week. Daily outdoor concentrations of NO2 ranged from 4.3 to 29.8 μg/m3, with a geometric mean of 12.3 μg/m3. There was no evidence of seasonal variation in outdoor concentrations. No significant correlation was found between each childs weekly mean personal exposures to NO2 and mean outdoor concentrations for the corresponding periods. CONCLUSION At low outdoor NO2 concentrations, fluctuations in NO2in outdoor air as measured at a central monitoring station do not contribute importantly to variations in personal exposure when averaged over a week.

O34-2 Insomnia and the older worker: findings from the health and employment after fifty (HEAF) study

Background Sleep disturbance is highly prevalent among people of working age, and has been linked with negative occupational outcomes including impaired productivity, absenteeism, risk of injuries, and health-related job loss. We aimed to describe the epidemiology of insomnia in HEAF, a cohort study of 50–64 year-olds from 24 English general practices, and to explore the relative importance of different occupational risk factors for insomnia. Methods Data came from the baseline questionnaire of the HEAF study. Participants reported on four problems with their sleep in the past 3 months, and insomnia was defined as having at least one severe problem. Socio-demographic variables, employment conditions and feelings about work were also ascertained. Analysis was restricted to those who answered the question on sleep disturbance (N = 8,067) and for the occupational analyses, to those in work (N = 5,470). Associations were assessed by logistic regression with adjustment for age and sex, and population attributable fractions (PAFs) were also computed. Results Insomnia was reported by 18.8% of the participants. It was more common among women, current smokers, manual social classes, and in those with lower educational level, living alone, experiencing financial hardship and who were obese. It was less prevalent among older people and those socialising with friends. Unemployed people tended to report more insomnia (OR = 3.1, 95% CI: 2.6–3.8), as did those in shift work (OR = 1.4, 95% CI: 1.2–1.7), dissatisfied with their job (OR = 3.9, 95% CI: 3.1–4.9), and rarely feeling appreciated (OR = 2.5, 95% CI: 2.1–3.1), or feeling unfairly criticised at work (OR = 4.2, 95% CI: 3.0–6.1). Population burden of insomnia was associated particularly with difficulties in coping with work demands, job insecurity and difficult colleagues (PAFs 17–33%). Conclusions Our data suggest that insomnia may be linked to several workplace elements that are potentially avoidable through better employment practices and policies.