A cross-sectional study to collect risk factors associated with stillbirths in pig herds

The aim of this study was to identify risk factors for stillborn piglets at herd level in commercial pig herds. A written questionnaire, containing semi-open questions directly or indirectly related to stillborn piglets, was sent to 250 randomly selected pig herds (>150 sows) in northern Belgium. In total 111/250 questionnaires were returned (response rate of 44.4%) and 107 were valid for analysis. The average reported frequency of stillbirth was 7.5% (S.D. 2.8%). The relationship between risk factors and stillbirths was evaluated with a generalized linear effects model with the percentage of stillborn piglets as outcome variable. Type of breed used on the farm was significantly (P < 0.01) associated with the percentage of stillborn piglets. A high temperature in the farrowing unit (≥22 °C compared to <22 °C) was associated with significantly (P < 0.01) more stillbirths, whereas showering sows with warm water before parturition resulted in significantly less stillbirths (5.8%) than no showering (7.7%) (P < 0.01) and was not significantly different from showering with cold water (7.0%) (P = 0.26). When supervision of farrowing was performed occasionally, significantly more stillbirths (8.1%) were observed in comparison with no attending to farrowing (6.5%) (P < 0.01) or frequent supervision of farrowing (6.9%) (P < 0.01). Significant interactions were found between breed and showering sows prior parturition or supervision of sows at parturition, and between temperature in the farrowing unit at parturition and showering procedure of the sows. In conclusion, this study has clearly demonstrated that breed is a major factor involved in the frequency of stillbirth. Additionally, some management practices before or at parturition may reduce the number of stillborn piglets.     

A large cross-sectional community-based study of newborn care practices in southern Tanzania

Despite recent improvements in child survival in sub-Saharan Africa, neonatal mortality rates remain largely unchanged. This study aimed to determine the frequency of delivery and newborn-care practices in southern Tanzania, where neonatal mortality is higher than the national average. All households in five districts of Southern Tanzania were approached to participate. Of 213,220 female residents aged 13-49 years, 92% participated. Cross-sectional, retrospective data on childbirth and newborn care practices were collected from 22,243 female respondents who had delivered a live baby in the preceding year. Health facility deliveries accounted for 41% of births, with nearly all non-facility deliveries occurring at home (57% of deliveries). Skilled attendants assisted 40% of births. Over half of women reported drying the baby and over a third reported wrapping the baby within 5 minutes of delivery. The majority of mothers delivering at home reported that they had made preparations for delivery, including buying soap (84%) and preparing a cloth for drying the child (85%). Although 95% of these women reported that the cord was cut with a clean razor blade, only half reported that it was tied with a clean thread. Furthermore, out of all respondents 10% reported that their baby was dipped in cold water immediately after delivery, around two-thirds reported bathing their babies within 6 hours of delivery, and 28% reported putting something on the cord to help it dry. Skin-to-skin contact between mother and baby after delivery was rarely practiced. Although 83% of women breastfed within 24 hours of delivery, only 18% did so within an hour. Fewer than half of women exclusively breastfed in the three days after delivery. The findings suggest a need to promote and facilitate health facility deliveries, hygienic delivery practices for home births, delayed bathing and immediate and exclusive breastfeeding in Southern Tanzania to improve newborn health.     

Sero-prevalence of anti-Leptospira antibodies and associated risk factors in rural Rwanda: A cross-sectional study

BackgroundLeptospirosis is a zoonotic disease transmitted through the urine of wild and domestic animals, and is responsible for over 50,000 deaths each year. In East Africa, prevalence varies greatly, from as low as 7% in Kenya to 37% in Somalia. Transmission epidemiology also varies around the world, with research in Nicaragua showing that rodents are the most clinically important, while studies in Egypt and Chile suggest that dogs may play a more important role. There are no published studies of leptospirosis in Rwanda.Methods & findingsWe performed a cross-sectional survey of asymptomatic adults recruited from five occupational categories. Serum samples were tested using ELISA and Microscopic Agglutination Test (MAT). We found that 40.1% (151/377) of asymptomatic adults had been exposed to Leptospira spp. Almost 36.3% of positive subjects reported contact with rats (137/377) which represent 90.7% among positive leptospira serology compared with 48.2% of negative subjects (182/377) which represent 80.5% among negative leptospira serology (OR 2.37, CI 1.25–4.49) and 1.7 fold on prevalence ratio and 2.37 of odd ratio. Furthermore, being a crop farmer was significantly associated with leptospirosis (OR 2.06, CI 1.29–3.28). We identified 6 asymptomatic subjects (1.6%) who met criteria for acute infection.ConclusionsThis study demonstrates a high prevalence of leptospiral antibodies infection among asymptomatic adults in rural Rwanda, particularly relative to neighboring countries. Although positive subjects were more likely to report rat contact, we found no independent association between rats and leptospirosis infection. Nonetheless, exposure was high among crop farmers, which is supportive of the hypothesis that rats together with domestic livestock might contribute to the transmission.Further studies are needed to understand infecting Leptospira servers and elucidate the transmission epidemiology in Rwanda and identify means of host transmitters.     

A cross-sectional study of people with epilepsy and neurocysticercosis in Tanzania: clinical characteristics and diagnostic approaches

Neurocysticercosis (NCC) is a major cause of epilepsy in regions where pigs are free-ranging and hygiene is poor. Pork production is expected to increase in the next decade in sub-Saharan Africa, hence NCC will likely become more prevalent. In this study, people with epilepsy (PWE, n=212) were followed up 28.6 months after diagnosis of epilepsy. CT scans were performed, and serum and cerebrospinal fluid (CSF) of selected PWE were analysed. We compared the demographic data, clinical characteristics, and associated risk factors of PWE with and without NCC. PWE with NCC (n=35) were more likely to be older at first seizure (24.3 vs. 16.3 years, p=0.097), consumed more pork (97.1% vs. 73.6%, p=0.001), and were more often a member of the Iraqw tribe (94.3% vs. 67.8%, p=0.005) than PWE without NCC (n=177). PWE and NCC who were compliant with anti-epileptic medications had a significantly higher reduction of seizures (98.6% vs. 89.2%, p=0.046). Other characteristics such as gender, seizure frequency, compliance, past medical history, close contact with pigs, use of latrines and family history of seizures did not differ significantly between the two groups. The number of NCC lesions and active NCC lesions were significantly associated with a positive antibody result. The electroimmunotransfer blot, developed by the Centers for Disease Control and Prevention, was more sensitive than a commercial western blot, especially in PWE and cerebral calcifications. This is the first study to systematically compare the clinical characteristics of PWE due to NCC or other causes and to explore the utility of two different antibody tests for diagnosis of NCC in sub-Saharan Africa.     

Some factors associated with condom use among bar maids in Tanzania

Some socioeconomic and demographic factors contributing to the use of condoms among bar maids were studied in selected urban areas in Tanzania. Bar maids were classified according to whether or not they use condoms, and logistic regression was used in the analysis. Of the demographic variables studied, age, marital status, education level, use of alcohol and wage rate showed a significant relationship at the 1% level between individual factors and use of condoms. The odds ratios show that girls aged 10-14 are over 18,000 times more likely not to use condoms compared with women aged 30 and above. Those who drink are 6.6 times (1/0.165) less likely to use condoms compared with those who do not drink. In other words, alcohol consumption can be a stimulus for an individual not to use condoms. It is clear that young girls who drink are at the highest risk of contracting HIV/AIDS in comparison with older females. A multiple logistic regression model shows all the aforementioned factors to be significant at the 1% level. A policy recommendation is made that the government should impose restrictions as far as employment of bar maids is concerned.     

Health-related quality of life and associated factors among Onchocerciasis patients in southeast Nigeria: A cross-sectional comparative study

IntroductionOnchocerciasis, a neglected tropical disease of public health importance, causes chronic morbidity and severe disability that may impact on health-related quality of life (HRQoL) of the infected people. This study assessed the HRQoL and associated factors among onchocerciasis patients in southeast Nigeria.MethodsThis was a community-based cross-sectional comparative study. Using a multistage sampling technique, 340 onchocerciasis patients were selected and matched for age and gender with the healthy population in the same neighbourhood. The respondents were interviewed using the short-form-36 (SF-36) questionnaire to determine their HRQoL. WHO Disability Assessment Schedule 2.0 tool (WHODAS 2.0) was used to assess disability in persons with onchocerciasis. Means were compared with independent student t-test while Chi-square test was used to compare proportions. Also, correlation analysis and logistic regression were used in the analyses.ResultsA significantly lower proportion of people living with onchocerciasis had a good quality of life when compared with the healthy subjects (69.4% vs 93.5%, p<0.001). Also, an inverse relationship was seen between disability and quality of life in the onchocerciasis group (r = -0.647, p<0.001). Predictors of poor quality of life among respondents with onchocerciasis were: respondents aged ≥48 years (AOR = 2.5, 95% CI: 1.4–5.0), those with some disability associated with onchocerciasis (AOR = 3.33, 95%CI: 1.4–5.0) and respondents who perceived themselves as a burden to people (AOR = 10, 95%CI: 2.5–20).ConclusionOnchocerciasis impacted negatively on HRQoL of persons with onchocerciasis when compared with the healthy population. The quality of life of persons affected with onchocerciasis reduces with increasing disability. There is the need to increase community awareness on onchocerciasis to ensure early diagnosis and prompt treatment as this will reduce disability among those affected with the disease thus enhancing their HRQoL.     

Prevalence of and risk factors associated with alcohol abuse in Moshi, northern Tanzania

This study aimed to assess the prevalence of and risk factors associated with alcohol abuse among women and men in Moshi in northern Tanzania. Alcohol abuse was measured by a CAGE score of 2-4, versus 0-1 for no alcohol abuse (Ewing, 1984). Crude and adjusted logistic regression models determined odds ratios (OR) and 95% confidence intervals (95% CI) of alcohol abuse by characteristics of, respectively, women with partners (n=1200), women without partners (n=614) and men (n=788) (women's partners). Prevalence of alcohol abuse was 7.0% (95% CI: 5.6-8.4) among women with partners, 9.3% (95% CI: 7.0-11.6) among women without partners, and more than double among men at 22.8% (95% CI: 19.9-25.8). In general, Christians had higher alcohol abuse than Muslims or other religions, as did Chagga men compared with men of other ethnic groups. Other socio-demographic characteristics, such as education or income, were not significant. Sexual behaviours were significant predictors of alcohol abuse. For example, women without partners who reported more than two partners in the last year had higher alcohol abuse compared with women reporting no partners (OR=8.75; 95% CI: 2.37-32.31), as did men reporting it is 'OK to hit a partner' for any reason (OR=1.79; 95% CI: 1.16-2.77) compared with men who did not. HIV-1 infection was not significantly associated with alcohol abuse by women or men. The Christian Church in Moshi should consider raising awareness about the harmful effects of high alcohol use among its adherents. Comprehensive programmes focusing on reducing number of partners and alcohol use, particularly by men, are needed in this community.     

A Japanese cross-sectional multicentre study of biomarkers associated with cardiovascular disease in smokers and non-smokers

Abstract

We performed a cross-sectional, multicentre study in Japan to detect the differences in biomarkers of exposure and cardiovascular biomarkers between smokers and non-smokers. Several clinically relevant cardiovascular biomarkers differed significantly between smokers and non-smokers, including lipid metabolism (high-density lipoprotein cholesterol concentrations – lower in smokers), inflammation (fibrinogen and white blood cell count – both higher in smokers), oxidative stress (8-epi-prostaglandin F_2α – higher in smokers) and platelet activation (11-dehydro-thromboxane B₂ – higher in smokers) (p ≤ 0.0001). These results provide further evidence showing that cardiovascular biomarkers can discriminate smokers from non-smokers, and could be used to evaluate the risks associated with tobacco products.     

Factors associated with self-rated health status of older people with multimorbidity in Colombia: A cross-sectional study

Background and objectiveIn Colombia, older adults (60 years and older) are expected to represent 15.5% of the overall population by 2025. Consequently, the demand for social and healthcare services will increase, especially because of the numerous medical conditions associated with aging. The purpose of the present study was to determine the patient's self-rated health status of older adults with multimorbidity and its determining factors based on gender in an insurance company of the Colombian health system.MethodologyA cross-sectional study was performed to analyze the sociodemographic and clinical characteristics of 438 patients older than 75 years as well as their self-rated health status (EQ-5D-3L questionnaire) during the first geriatric consultation of a comprehensive healthcare program. A multivariate linear regression analysis was performed to identify factors determining their self-rated health status.ResultsWomen had a worse self-rated health status than men [mean (standard deviation) EQ-5D index score: 0.77 (0.20) vs. 0.65 (0.18); p < 0.001]. In all sample, factors independently associated with self-rated health status were self-perception of weakness and dependency. In men, additional factors related to EQ-5D index were low levels of physical activity, recurrent falls, fecal incontinence, and auditory and visual disorders. In women, other health-determining factors were decrease in walking speed, and a medical history of depression/anxiety.ConclusionsFactors associated with the self-rated health status of older adults who were part of a comprehensive healthcare program in Colombia varied according to gender. This study will help in approaching health interventions in healthcare programs for older adults in a differentiated manner.     

Prevalence of exclusive breastfeeding and associated factors among mothers in rural Bangladesh: a cross-sectional study

Background

Exclusive breastfeeding (EBF) means that the infant receives only breast milk for the first six months of life after birth. In Bangladesh, the prevalence of EBF remained largely unchanged for nearly two decades and was 43% in 2007. However, in 2011, a prevalence of 64% was reported, an increase by 21 percentage points. The reasons for this large change remain speculative at this point. Thus to investigate the issue further, this study was conducted. The objective was to assess the prevalence of EBF and associated factors among mothers having children aged 0–6 months in rural Bangladesh.

Methods

A cross-sectional study was conducted in Mirzapur Upazilla (sub district) among 121 mothers of infants aged 0–6 months. Eligible mothers were identified and randomly selected using the demographic surveillance system’s computerized database that is updated weekly. A semi-structured questionnaire was used for interviews that inquired information on socio-demographic characteristics, obstetric, health service, breastfeeding related factors (initiation of breastfeeding, prelacteal feeding and colostrum feeding) and economic factors. EBF prevalence was calculated using 24 hour recall method. In multivariate analysis, a logistic regression model was developed using stepwise modeling to analyze the factors associated with EBF.

Results

The prevalence of EBF in the last 24 hours preceding the survey was 36%. Bivariate and multivariate analysis revealed no significant association between EBF and its possible predictors at 0.05 level of alpha. However, there was some evidence of an association between EBF and having a caesarean delivery (OR?=?0.47, 95% CI: 0.21, 1.06). In multivariate analysis, type of delivery: caesarean (AOR?=?0.45, 95% CI: 0.19, 1.03) and wealth quintile: richer (AOR?=?2.40, 95% CI: 0.94, 6.16) also showed some evidence of an association with EBF.

Conclusion

The prevalence of EBF in Mirzapur (36%) is lower than the national figure (64%). Prelacteal feeding was not uncommon. These findings suggest that there is a need for breastfeeding support provided by health services. Hence, promotion of EBF during the first six months of life needs to be addressed and future breastfeeding promotion programmes should give special attention to those women who are not practicing EBF.

     

Environmental factors and hygiene behaviors associated with facial cleanliness and trachoma in Kongwa,Tanzania

BackgroundHaving a clean face is protective against trachoma. In the past, long distances to water were associated with unclean faces and increased trachoma. Other environmental factors have not been extensively explored. We need improved clarity on the environmental factors associated with facial cleanliness and trachoma prevalence, especially when the disease burden is low.Methodology/Principle findingsA cross-sectional survey focusing on household environments was conducted in all 92 villages in Kongwa, Tanzania, in a random selection of 1798 households. Children aged 0–5 years in these households were examined for facial cleanliness. In each of the 50 randomly-selected villages, 50 children aged 1–9 years were randomly selected and examined for trachoma. In a multivariate model adjusting for child age, we found that children were more likely to have clean faces if the house had a clean yard (OR 1.62, 95% CI 1.37–1.91), an improved latrine (OR 1.11, 95% CI 1.01–1.22), and greater water storage capacity (OR 1.02, 95% CI 1.00–1.04), and if there were clothes washed and drying around the house (OR 1.30, 95% CI 1.09–1.54). However, measures of crowding, wealth, time spent on obtaining water, or the availability of piped water was not associated with clean faces. Using a cleanliness index (clean yard, improved latrine, washing clothes, ≥1 child in the household having a clean face), the community prevalence of trachoma decreased with an increase in the average value of the index (OR 2.28, 95% CI 1.17–4.80).Conclusions/SignificanceAccess to water is no longer a significant limiting factor in children’s facial cleanliness in Kongwa. Instead, water storage capacity and the way that water is utilized are more important in facial cleanliness. A household cleanliness index with a holistic measure of household environment is associated with reduced community prevalence of trachoma.     

Spatial and management factors associated with exposure of smallholder dairy cattle in Tanzania to tick-borne pathogens

A cross-sectional study of serum antibody responses of cattle to tick-borne pathogens (Theileria parva, Theileria mutans,Anaplasma marginale, Babesia bigemina and Babesia bovis) was conducted on smallholder dairy farms in Tanga and Iringa Regions of Tanzania. Seroprevalence was highest for T. parva (48% in Iringa and 23% in Tanga) and B. bigemina (43% in Iringa and 27% in Tanga) and lowest for B. bovis (12% in Iringa and 6% in Tanga). We use spatial and non-spatial models, fitted using classical and Bayesian methods, to explore risk factors associated with seroprevalence. These include both fixed effects (age, grazing history and breeding status) and random effects (farm and local spatial effects). In both regions, seroprevalence for all tick-borne pathogens increased significantly with age. Animals pasture grazed in the 3 months prior to the start of the sampling period were significantly more likely to be seropositive for Theileria spp. and Babesia spp. Pasture grazed animals were more likely to be seropositive than zero-grazed animals for A. marginale, but the relationship was weaker than that observed for the other four pathogens. This study did not detect any significant differences in seroprevalence associated with other management-related variables, including the method or frequency of acaricide application. After adjusting for age, there was weak evidence of localised (<5 km) spatial correlation in exposure to some of the tick borne diseases. However, this was small compared with the 'farm-effect', suggesting that risk factors specific to the farm were more important than those common to the local neighbourhood. Many animals were seropositive for more than one pathogen and the correlation between exposure to the different pathogens remained after adjusting for the identified risk factors. Identifying the determinants of exposure to multiple tick-borne pathogens and characterizing local variation in risk will assist in the development of more effective control strategies for smallholder dairy farms.     

Dog ownership during pregnancy, maternal activity, and obesity: a cross-sectional study

The Avon Longitudinal Study of Parents and Children (ALSPAC) is an observational study of 14,273 UK pregnant singleton mothers in 1990/1991. We examined outcomes of self report of strenuous activity (hours per week) at 18 and 32 weeks of gestation, hours spent in leisure-time physical activities and types, and pre-pregnancy body mass index (BMI); overweight status was defined as pre-pregnancy BMI≥25 and obesity BMI≥30. Pet ownership and activity data were reported for 11,466 mothers. Twenty-five percent of mothers owned at least one dog. There was a positive relationship between participation in activity at least once a week and dog ownership (at 18 weeks, Odds ratio 1.27, 95% confidence interval 1.11-1.44, P<0.001). Dog owners were 50% more likely to achieve the recommended 3 hours activity per week, equivalent to 30 minutes per day, most days of the week (1.53, 1.35-1.72, P<0.001). Dog owners were also more likely to participate in brisk walking activity than those who did not have a dog (compared to no brisk walking 2-6 hrs per week 1.43, 1.23 to 1.67, P<0.001; 7+ hrs per week 1.80, 1.43 to 2.27, P<0.001). However, no association was found with any other types of activities and there was no association between dog ownership and weight status. During the time period studied, pregnant women who had dogs were more active, through walking, than those who did not own dogs. As walking is a low-risk exercise, participation of pregnant women in dog walking activities may be a useful context to investigate as part of a broader strategy to improve activity levels in pregnant women.     

Thrombus size is associated with etiology of deep venous thrombosis--a cross-sectional study

The aim of this study was to evaluate the impact of risk factors for deep vein thrombosis (DVT) on thrombus sizes in lower extremities. The size and extent of thrombus was scored according to International Consensus Committee for venous disease classification. After the diagnosis of DVT was established and its size scored, predominant risk factors for DVT in each patient were identified (malignant disease, thrombophilia, postoperative state, hormonal therapy, heredity, limb trauma, immobilization, others and unknown risk factors). The average thrombus score was 6 (95% CI 5.47-6.53). The analysis of thrombus size indicated that the largest thrombi were found in patients with malignancy. Their average score was 8.5 (95% CI 7-10) and was significantly higher than in patients with other risk factors for deep vein thrombosis. There was no significant correlation between numbers of days from the onset of symptoms to the moment of DVT diagnosis and thrombus score (r = -0.08, p = 0.38). Age was very slightly correlated to thrombus size (r = 0.19; p = 0.046), while the gender did not have significant impact on thrombus score (p = 0.074). The conclusion of our study was that etiology of thrombosis and particularly malignant diseases has the largest impact on venous thrombus size.     

Association of iron metabolism markers,socioeconomic and lifestyle factors with endometriosis: A cross-sectional study

BackgroundEvidence on the link between iron metabolism markers and endometriosis is limited. We aimed to investigate the associations of iron metabolism markers, including serum ferritin level and transferrin saturation, with endometriosis.MethodsThis study involved 6551 participants from the National Health and Nutrition Examination Survey (NHANES). Univariable and multivariable logistic regression analyses were used to examine the linear relationships between iron metabolism markers and endometriosis. Furthermore, restricted cubic splines were used to identify the non-linear dose-response associations.ResultsUnivariable analysis showed that the factors associated with endometriosis included age, race, education level, and smoking status. In multivariable model, compared with lowest quartile, highest quartile of serum ferritin level was positively associated with endometriosis (OR: 2.11, 95% confidence intervals [CI]: 1.31, 3.40, P = 0.004), and third quartile of transferrin saturation positively associated with endometriosis (OR: 1.55, 95% CI: 1.05, 2.29, P = 0.033). The restricted cubic splines showed the non-linear (inverted U-shape) associations between serum ferritin level and transferrin saturation and endometriosis (all P for non-linear＜0.01), indicating that the ORs of endometriosis increased with serum ferritin level and transferrin saturation up to the turning point and thereafter the ORs of endometriosis did not significantly increase with the increasing serum ferritin and transferrin saturation.ConclusionsOur findings suggests that serum ferritin level and transferrin saturation were positively associated with endometriosis. Serum ferritin and transferrin saturation may be an important marker for endometriosis. Future prospective and longitudinal studies are necessary to better understand these findings.     

Prevalence and associated factors of elder mistreatment in a rural community in People's Republic of China: a cross-sectional study

Background

Current knowledge about elder mistreatment is mainly derived from studies done in Western countries, which indicate that this problem is related to risk factors such as a shared living situation, social isolation, disease burden, and caregiver strain. We know little about prevalence and risk factors for elder mistreatment and mistreatment subtypes in rural China where the elder population is the most vulnerable.

Methods

In 2010, we conducted a cross-sectional survey among older adults aged 60 or older in three rural communities in Macheng, a city in Hubei province, China. Of 2245 people initially identified, 2039 were available for interview and this was completed in 2000. A structured questionnaire was used to collect data regarding mistreatment and covariates. Logistic regression analysis was used to identify factors related to elder mistreatment and subtypes of mistreatment.

Results

Elder mistreatment was reported by 36.2% (95% CI: 34.1%–38.3%) of the participants. Prevalence rates of psychological mistreatment, caregiver neglect, physical mistreatment, and financial mistreatment were 27.3% (95% CI: 25.3%–29.2%), 15.8% (95% CI: 14.2%–17.4%), 4.9% (95% CI: 3.9%–5.8%) and 2.0% (95% CI: 1.3%–2.6%), respectively. The multivariate logistic regression analysis revealed that depression, being widowed/divorced/single/separated, having a physical disability, having a labor intensive job, depending solely on self-made income, and living alone were risk factors for elder mistreatment. Different types of elder mistreatment were associated with different risk factors, and depression was the consistent risk factor for the three most common mistreatment subtypes.

Conclusion

Older adults in rural China self-report a higher rate of mistreatment than their counterparts in Western countries. Depression is a main risk factor associated with most subtypes of mistreatment. Our findings suggest that prevention and management of elder mistreatment is a challenge facing a rapidly aging Chinese population.     

Pilot study of factors associated with exacerbations in chronic bronchitis

The factors associated with exacerbations of chronic bronchitis were investigated in a pilot study of 23 male patients over a period of 29 months. There were 63 exacerbations—56 were fully investigated and in seven only serological studies were possible. Evidence of the presence of an infective agent was sought in the early stages of the exacerbations and during relative quiescence. Significantly more potential pathogens, both bacterial (pneumococci and Haemophilus influenzae) and viral and mycoplasmal, were found during exacerbations than in quiescent periods. It was not possible to demonstrate that atmospheric pollution or low temperature influenced exacerbations, but the data are insufficient to exclude a small effect.It is emphasized that the value of future work on these lines would be increased if agreement could be reached on the definition of an exacerbation.