An Epidemiological Study of Lung Cancer and Selected Other Cancers among Namibian Uranium Workers

The Rössing Uranium Limited (RUL) open-cast uranium mine in Namibia has operated since 1976. Studies of underground uranium miners from Europe and North America have shown increased cancer risks (principally lung cancer). We explored the association between radiation doses and selected cancers in RUL mineworkers. Employees with at least one-year of continuous employment between 1976 and 2010 were included. Incident cancer cases [lung, extra-thoracic airways (ETA), leukemia, brain and kidney] occurring before the end of 2015 were identified from the Namibian and South African National Cancer Registries, and RUL's occupational health provider. Using a case-cohort design, data on exposure and confounding factors were collected for all cancer cases among the study cohort and a stratified random sample (sub-cohort) of the cohort, including cases. Radiation doses were estimated based on annual dose records held by RUL. In total, 76 cancer cases (32 lung, 18 ETA, 8 leukemia, 9 brain, 9 kidney) and a sub-cohort of 1,121 sampled from 7,901 RUL employees were included. A weighted Cox model, adjusted for available known confounders, produced a rate ratio (95% CI) for lung cancer of 1.42 (0.42, 4.77) and 1.22 (0.26, 5.68), respectively, for medium and higher cumulative lung dose categories compared to the lower category, and 1.04 (0.95, 1.13) for a dose increase of 10 mSv. This study faced considerable challenges with respect to case ascertainment, exposure estimates, and ensuring accuracy of key variables. Persuasive consistent evidence for elevated cancer risk was not found for radiation or other exposures studied at the Rössing uranium mine.

Phytoestrogen intake and other dietary risk factors for low motile sperm count and poor sperm morphology

BACKGROUND

Few potentially modifiable risk factors of male infertility have been identified, and while different diets and food groups have been associated with male infertility, evidence linking dietary factors including phytoestrogens and semen quality is limited and contradictory.

OBJECTIVES

To study the associations between phytoestrogen intake and other dietary factors and semen quality.

MATERIALS AND METHODS

A case-referent study was undertaken of the male partners, of couples attempting conception with unprotected intercourse for 12 months or more without success, recruited from 14 UK assisted reproduction clinics. A total of 1907 participants completed occupational, lifestyle and dietary questionnaires before semen quality (concentration, motility and morphology) were assessed. Food intake was estimated by a 65-item food frequency questionnaire (FFQ) covering the 12 months prior to recruitment. Analyses of dietary risk factors for low motile sperm concentration (MSC: <4.8 × 10⁶ /mL) and poor sperm morphology (PM: <4% normal morphology) used unconditional logistic regression, accounting for clustering of subjects within the clinics, first without, and then with, adjustment for confounders associated with that outcome.

RESULTS

High consumption of daidzein (≥13.74 μg/d), a phytoestrogen found in soy products, was a protective factor for MSC with an odds ratio (95%CI) of 0.58 (0.42-0.82) after adjustment for clustering and potential confounding. Dietary risk factors for PM after similar adjustment showed that drinking whole milk (OR 0.67, 95%CI 0.47-0.96) and eating red meat were protective with an OR 0.67 (0.46-0.99) for eating red meat >3 times/wk.

DISCUSSION

In this case-referent study of men attending an infertility clinic for fertility diagnosis, we have identified that low MSC is inversely associated with daidzein intake. In contrast, daidzein intake was not associated with PM but eating red milk and drinking whole milk were protective.

CONCLUSIONS

Dietary factors associated with semen quality were identified, suggesting that male fertility might be improved by dietary changes.

Scores Obtained from a Simple Cognitive Test of Visuospatial Episodic Memory Performed Decades before Death Are Associated with the Ultimate Presence of Alzheimer Disease Pathology

BACKGROUND

Community- or population-based longitudinal studies of cognitive ability with a brain donation end point offer an opportunity to examine relationships between pathology and cognitive state prior to death. Discriminating the earliest signs of dementing disorders, such as Alzheimer disease (AD), is necessary to undertake early interventions and treatments.

METHODS

The neuropathological profile of brains donated from The University of Manchester Longitudinal Study of Cognition in Normal Healthy Old Age, including CERAD (Consortium to Establish a Registry for Alzheimer's Disease) and Braak stage, was assessed by immunohistochemistry. Cognitive test scores collected 20 years prior to death were correlated with the extent of AD pathology present at death.

RESULTS

Baseline scores from the Memory Circle test had the ability to distinguish between individuals who developed substantial AD pathology and those with no, or low, AD pathology. Predicted test scores at the age of 65 years also discriminated between these pathology groups. The addition of APOE genotype further improved the discriminatory ability of the model.

CONCLUSIONS

The results raise the possibility of identifying individuals at future risk of the neuropathological changes associated with AD over 20 years before death using a simple cognitive test. This work may facilitate early interventions, therapeutics and treatments for AD by identifying at-risk and minimally affected (in pathological terms) individuals.

An Assessment of Radiation-Associated Risks of Mortality from Circulatory Disease in the Cohorts of Mayak and Sellafield Nuclear Workers

Mortality from circulatory disease (CD), ischemic heart disease (IHD) and cerebrovascular disease (CeVD) was investigated in relationship to cumulative doses of external gamma radiation and internal alpha radiation to the liver from deposited plutonium over long follow-up periods in two large cohorts of nuclear workers: the Russian Mayak Worker Cohort (MWC) and the UK Sellafield Worker Cohort (SWC). The MWC comprised 22,374 workers (74.6% males) with 5,123 CD deaths registered during 842,538 person-years of follow-up, while the SWC comprised 23,443 workers (87.8% males) with 2,322 CD deaths registered during 602,311 person-years of follow-up. Dose estimates for external gamma radiation and internal alpha radiation to the liver were calculated via a common methodology, in accordance with an agreed protocol. The mean cumulative external H_p(10) dose was 0.52 Sv for the MWC and 0.07 Sv for the SWC, while the mean cumulative internal dose was 0.19 Gy for the MWC and 0.01 Gy for the SWC. Categorical relative risks (RR) and excess relative risks (ERR) per unit dose were estimated for each cohort and for the pooled cohort when appropriate. The dose responses for CD, IHD and CeVD in relationship to internal alpha-particle dose did not differ significantly from the null for either the MWC, the SWC or the pooled plutonium worker cohort. The ERR/Sv estimates in relationship to external exposure were significantly raised for both cohorts (marginally so for the MWC) for CD and IHD (but not for CeVD), but differed significantly between the two cohorts, the estimate for the SWC being approximately ten times greater than that for the MWC. Examination of the ERR/Sv estimates for two periods of first employment at the two facilities revealed that the significant heterogeneity was confined to the earlier sub-cohorts, and that the estimates for the later sub-cohorts were compatible. The two sub-cohorts for the later first-employment periods were pooled, producing risk estimates that were raised, but not significantly so: ERR/Sv for CD, IHD and CeVD of 0.22 (95% CI: -0.01, 0.49), 0.22 (95% CI: -0.06, 0.57) and 0.24 (95% CI: -0.17, 0.80), respectively. The reasons for the complex pattern of results found in this study are unclear. Among potential explanations are the influence of differences in background CD mortality rates, an effect of other occupational factors, substantial uncertainties in doses, particularly during earlier periods of operations, as well as confounding and/or modifying factors that were not taken into account in the current analysis.

How serious is bias in effect estimation in randomised trials with survival data given risk heterogeneity and informative censoring?

It is often assumed that randomisation will prevent bias in estimation of treatment effects from clinical trials, but this is not true of the semiparametric Proportional Hazards model for survival data when there is underlying risk heterogeneity. Here, a new formula is proposed for estimation of this bias, improving on a previous formula through ease of use and clarity regarding the role of the mid-study cumulative hazard rate, shown to be an important factor for the bias magnitude. Informative censoring (IC) is recognised as a source of bias. Here, work on selection effects among survivors due to risk heterogeneity is extended to include IC. A new formula shows that bias in causal effect estimation under IC has two sources: one consequent on heterogeneity and one from the additional impact of IC. The formula provides new insights not previously shown: there may less bias under IC than when there is no IC and even, in principle, zero bias. When tested against simulated data, the new formulae are shown to be very accurate for prediction of bias in Proportional Hazards and accelerated failure time analyses which ignore heterogeneity. These data are also used to investigate the performance of accelerated failure time models which explicitly model risk heterogeneity ('frailty models') and G estimation. These methods remove bias when there is simple censoring but not with informative censoring when they may lead to overestimation of treatment effects. The new formulae may be used to help researchers judge the possible extent of bias in past studies. Copyright © 2017 John Wiley & Sons, Ltd.

Changes in selected metabolic parameters in patients over 65 receiving hydrochlorothiazide plus amiloride, atenolol or placebo in the MRC elderly trial

Background

Treatment of hypertension reduces incidence of stroke, myocardial infarction and heart failure perhaps partly by controlling different metabolic parameters. There is limited information regarding the changes in potassium, sodium, weight, cholesterol and glucose levels in patients using anti-hypertensives. This study aimed to determine changes in potassium, sodium, glucose, cholesterol, weight, urea and urate levels in patients using anti-hypertensives. Furthermore, to describe these changes and differences between the atenolol, hydrochlorothiazide plus amiloride and placebo arms of the Medical Research Council (MRC) elderly randomised controlled trial.

Methods

Patients were randomly allocated to one of the three treatment arms. Measurements were taken at baseline, end of year one and end of year two in 4396 subjects. Linear Mixed Models (LMM) were used to determine the longitudinal profiles of sodium, potassium, weight, cholesterol, glucose, urea and urate. Estimates of changes within groups and difference between groups were obtained.

Results

Patients randomised to receive hydrochlorothiazide + amiloride experienced a significantly greater mean reduction in potassium, sodium and weight compared to placebo at end of year one - mean differences in change −0.18 mmol/L, (95 % CI: −0.21, −0.15); −1.45 mmol/L, (95 % CI: −1.62, −1.29) and −0.46 kgs (95 % CI: −0.73, −0.20) respectively, and greater increases in cholesterol, urea and urate - mean differences in change 0.16 mmol/L, (95 % CI: 0.10,0.22); 0.77 mmol/L, (95 % CI: 0.68, 0.87) and 53.10 μmol/L, (95 % CI: 49.35, 56.85) respectively. Changes were in the same direction but smaller in the atenololarm except for potassium and weight (increases). No group differences in glucose were found.

Conclusion

Results were in line with expectation except for lack of change in glucose in the hydrochlorothiazide + amiloride arms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0368-2) contains supplementary material, which is available to authorized users.

Assessing the reliability of ordered categorical scales using kappa-type statistics

Methods for the analysis of reliability of ordered categorical scales are discussed, focussing on the limitation of the single summary-weighted kappa coefficients. A symmetric matrix of kappa-type coefficients is suggested as an alternative. The method is proposed as being suitable for ordinal scale where there is no underlying continuum. Their application is illustrated using two data sets from reliability studies. If, instead, distances between categories can be specified, a weighted mean of the matrix terms can be used as a summary measure. This is equal to a weighted kappa coefficient with squared weights, provided distances between adjacent categories are equal. When a study design corresponds to a one-way random effects model, estimates of precision of kappa-type coefficient, including the coefficients described here, can be obtained using the delta-method, bootstrap resampling by subjects or jack-knifing by subjects. In the case of interobserver reliability studies, where there may be systematic differences between observers, the investigator may wish to generalise to a population of observers and subjects. In this case, jack-knifing by observer and subject is suggested. Empirical comparisons are made between standard error estimates based on the delta-method, on jack-knifing by subjects and a two-way jack-knife by subjects and observers. The results suggest that standard errors based on the delta-method or jack-knifing by subject alone may be overly precise.

Gestational Age and Birth Weight and the Risk of Childhood Type 1 Diabetes: A Population-Based Cohort and Sibling Design Study

OBJECTIVE

We investigated the effects of gestational age, birth weight, small for gestational age (SGA), and large for gestational age (LGA) on risk of childhood type 1 diabetes.

RESEARCH DESIGN AND METHODS

We conducted a population-based cohort study of all singleton live births in Sweden between 1973 and 2009 and a sibling control study. Perinatal data were extracted from the Swedish Medical Birth Register. Children with type 1 diabetes diagnosis were identified from the Swedish National Patient Register. Log-linear Poisson regression and conditional logistic regression were used for data analysis.

RESULTS

The study cohort consisted of 3,624,675 singleton live births (42,411,054 person-years). There were 13,944 type 1 diabetes cases during the study period. The sibling control study consisted of 11,403 children with type 1 diabetes and 17,920 siblings. Gestational age between 33 and 36 weeks (relative risk [RR] 1.18 [95% CI 1.09, 1.28) and 37 and 38 weeks (RR 1.12 [95% CI 1.07, 1.17]) was associated with type 1 diabetes in the cohort study and remained significant in the sibling control study. SGA (RR 0.83 [95% CI 0.75, 0.93]) and LGA (RR 1.14 [95% CI 1.04, 1.24]) were associated with type 1 diabetes in the cohort study. The SGA association remained unchanged in the sibling study, while the LGA association disappeared. Very low birth weight was associated with a reduced risk of type 1 diabetes.

CONCLUSIONS

The findings suggest a small association between gestational age and type 1 diabetes that is not likely due to familial confounding factors. Gestational age and type 1 diabetes may be related to insulin resistance due to early life growth restriction or altered gut microbiota in preterm babies.

The impact of national-level interventions to improve hygiene on the incidence of irritant contact dermatitis in healthcare workers: changes in incidence from 1996 to 2012 and interrupted times series analysis

BACKGROUND

Reducing healthcare-associated infections (HCAI) has been a priority in the U.K. over recent decades and this has been reflected in interventions focusing on improving hygiene procedures.

OBJECTIVES

To evaluate whether these interventions coincided with an increased incidence of work-related irritant contact dermatitis (ICD) attributed to hand hygiene or/and other hygiene measures in healthcare workers (HCWs).

METHODS

A quasi-experimental (interrupted time series) design was used to compare trends in incidence of ICD in HCWs attributed to hygiene before and after interventions to reduce HCAI with trends in the same periods in control groups (ICD in other workers). Cases of ICD reported to a U.K. surveillance scheme from 1996 to 2012 were analysed. The time periods compared were defined objectively based on the dates of the publication of national evidence-based guidelines, the U.K. Health Act 2006 and the Cleanyourhands campaign.

RESULTS

The reported incidence of ICD in HCWs attributed to hygiene has increased steadily from 1996 to 2012 [annual incidence rate ratio (95% confidence interval): hand hygiene only 1.10 (1.07-1.12); all hygiene 1.05 (1.03-1.07)], whereas the incidence in other workers is declining. An increase in incidence of ICD in HCWs attributed to hand hygiene was observed at the beginning of the Cleanyourhands campaign.

CONCLUSIONS

The increasing incidence of ICD in HCWs combined with the popularity of interventions to reduce HCAI warrants increased efforts towards identifying products and implementing practices posing the least risk of ICD.

Trends in incidence of occupational asthma, contact dermatitis, noise-induced hearing loss, carpal tunnel syndrome and upper limb musculoskeletal disorders in European countries from 2000 to 2012

OBJECTIVES

The European Union (EU) strategy for health and safety at work underlines the need to reduce the incidence of occupational diseases (OD), but European statistics to evaluate this common goal are scarce. We aim to estimate and compare changes in incidence over time for occupational asthma, contact dermatitis, noise-induced hearing loss (NIHL), carpal tunnel syndrome (CTS) and upper limb musculoskeletal disorders across 10 European countries.

METHODS

OD surveillance systems that potentially reflected nationally representative trends in incidence within Belgium, the Czech Republic, Finland, France, Italy, the Netherlands, Norway, Spain, Switzerland and the UK provided data. Case counts were analysed using a negative binomial regression model with year as the main covariate. Many systems collected data from networks of 'centres', requiring the use of a multilevel negative binomial model. Some models made allowance for changes in compensation or reporting rules.

RESULTS

Reports of contact dermatitis and asthma, conditions with shorter time between exposure to causal substances and OD, were consistently declining with only a few exceptions. For OD with physical causal exposures there was more variation between countries. Reported NIHL was increasing in Belgium, Spain, Switzerland and the Netherlands and decreasing elsewhere. Trends in CTS and upper limb musculoskeletal disorders varied widely within and between countries.

CONCLUSIONS

This is the first direct comparison of trends in OD within Europe and is consistent with a positive impact of European initiatives addressing exposures relevant to asthma and contact dermatitis. Taking a more flexible approach allowed comparisons of surveillance data between and within countries without harmonisation of data collection methods.

Investigating work-related neoplasia associated with solar radiation

BACKGROUND

Both solar and non-solar exposures associated with occupation and work tasks have been reported as skin carcinogens. In the UK, there are well-established surveillance schemes providing relevant information, including when exposures took place, occupation, location of work and dates of symptom onset and diagnosis.

AIMS

To add to the evidence on work-related skin neoplasia, including causal agents, geographical exposure and time lag between exposure and diagnosis.

METHODS

This study investigated incident case reports of occupational skin disease originating from clinical specialists in dermatology reporting to a UK-wide surveillance scheme (EPIDERM) by analysing case reports of skin neoplasia from 1996 to 2012 in terms of diagnosis, employment, suspected causal agent and symptom onset.

RESULTS

The suspected causal agent was 'sun/sunlight/ultraviolet light' in 99% of the reported work-related skin neoplasia cases. Most cases reported (91%) were in males, and the majority (62%) were aged over 65 at the time of reporting. More detailed information on exposure was available for 42% of the cases, with the median time from exposure to symptom onset ranging from 44 (melanoma) to 57 (squamous cell carcinoma) years. Irrespective of diagnostic category, the median duration of exposure to 'sun/sunlight/ultraviolet light' appeared longer where exposures occurred in the UK (range 39-51 years) rather than outside the UK (range 2.5-6.5 years).

CONCLUSIONS

It is important to provide effective information about skin protection to workers exposed to solar radiation, especially to outdoor workers based outside the UK.

Pesticide exposure and screen-positive neuropsychiatric disease in British sheep farmers

BACKGROUND

Epidemiological evidence linking low dose pesticide exposure and chronic ill-health in UK sheep farmers is limited. Our aim was to examine whether neuropsychiatric disorders were associated with low dose chronic and/or more acute pesticide exposure in sheep farmers.

METHODS

A cohort of British farmers working in the 1970s was sent a screening questionnaire which asked about their health and work history. The prevalence of screen-positive depression, dementia, Parkinsonism and neuropathy was determined using a priori algorithms. Self-reported pesticide exposure was assessed by whether the participant had ever handled the pesticide concentrate (for low dose chronic exposure) or sought advice for pesticide poisoning (acute exposure) and participants categorised into those with only acute or chronic exposure, those with both acute and chronic exposure and those with neither acute nor chronic exposure. Associations between acute and chronic pesticide exposure, and screen-positive ill-health were determined after adjustment for demographic, lifestyle, occupation and somatic severity scores and other variables.

RESULTS

In those participants, who had never sought advice for pesticide poisoning, handling the pesticide concentrate for treating sheep was associated with elevated ORs for screen-positive neuropathy (ORadi 1.57 95%CI 0.97-2.54) and Parkinsonism (ORadj 1.56 95%CI 0.95-2.56) but not depression or dementia. In those participants who had handled the pesticide concentrate, seeking advice for pesticide poisoning was associated with screen-positive depression (Odds ratio, ORadj=9.97 95%CI 4.76-20.8 ), dementia (OR=6.94 95%CI 3.44-14.0), Parkinsonism (ORadj=4.77 95% 2.39-9.52), and neuropathy (ORadj=4.77 95%CI 2.39-9.52). Adjustment for somatic severity score modified little the associations with pesticide handling in those not acutely exposed but reduced the ORs for seeking advice for pesticide poisoning in those exposed chronically. Furthermore, stratification of results based upon somatic severity score indicated that the highest ORs for handling the pesticide concentrate associated with neuropathy and Parkinsonism were found in those participants whose somatic score was minimal.

CONCLUSIONS

Results are consistent with low-dose exposure to pesticides being associated with screen-positive neuropathy and Parkinsonism but the stronger associations between seeking advice for pesticide poisoning and screen-positive ill-health suggest that acute pesticide exposure remains an important determinant of ill-health. Further work is required to better delineate to what extent low dose exposures may contribute to ill-health in populations without acute exposures. Somatising tendency does not appear to play an important role in this population.

Occupation exposures and sperm morphology: a case-referent analysis of a multi-centre study

OBJECTIVE

We examined occupational exposures and sperm morphology to establish whether exposures implicated differed from those affecting motile sperm concentration.

METHODS

Computer aided sperm morphometric assessment was undertaken on morphology slides obtained as part of a multi-centre study in 1999-2002 of occupational factors in male infertility. Men attending 14 fertility clinics across the UK were recruited and gave a semen sample. Before results of the semen analysis were known, the men completed detailed questionnaires about their employment and lifestyle. Occupational exposures were assessed by occupational hygienists. Data were analysed using an unmatched case-referent design, allowing for clustering and for confounders. Three case definitions were used: poor morphology (normal morphology <4%), low motile sperm count (MSC) (<4.8×10(6)) and either condition.

RESULTS

Morphology results were available for 1861/2011 men employed at the time of recruitment. Of these 1861, 296 (15.9%) had poor morphology; of the 2011with sperm count, 453 (22.5%) had low MSC; 654/1981 (33.0%) had either condition. Poor morphology, adjusted for confounding, was related to self-reported lifetime exposure to lead (OR=1.33; 95% CI 1.00 to 1.75). Low MSC was also related to self-reported lead and to hygienist-assessed glycol ether exposure. Self-reported use of paint stripper (OR=1.47; 95% CI 1.07 to 2.03) and lead, but not glycol ether, were significantly related to the combined case definition.

CONCLUSIONS

While this study did not identify any occupational exposure uniquely related to sperm morphology, the capacity of the study to detect risk was increased by including morphology with sperm concentration and motility.

Long-term safety of unopposed estrogen used by women surviving myocardial infarction: 14-year follow-up of the ESPRIT randomised controlled trial

OBJECTIVE

To compare health outcomes during 14-year observational follow-up in women initially randomised to unopposed estrogen or placebo.

DESIGN

At recruitment to the Estrogen for the Prevention of Re-Infarction Trial (ESPRIT) women were assigned to estradiol valerate: 2 mg or placebo treatment for 2 years.

SETTING

Women were recruited from 35 hospitals in the northwest of England and Wales in July 1996-February 2000.

SAMPLE

Women aged 50-69 surviving their first myocardial infarction.

METHODS

All women were followed by data linkage to UK mortality and cancer records; mean follow-up 14.1 and 12.6 years, respectively. In an intention-to-treat analysis, hazard ratios (HRs) were computed, overall and stratified by age at recruitment.

OUTCOME MEASURES

Death (all-cause, cardiac disease, stroke or cancer) and cancer incidence (any, breast or endometrium).

RESULTS

There were 418 deaths in 1017 women randomised. The all-cause mortality HR of 1.07 (95% CI 0.88-1.29) indicated no significant difference between treatment groups. Women aged 50-59 years at recruitment had lower HRs than women aged 60-69 years for all outcomes except ischaemic heart disease. Among 149 incident cancers there were seven cases of breast cancer in the intervention arm and 15 in the placebo; HR 0.47 (95% CI 0.19-1.15). There were no deaths from endometrial cancer but three incident cases, one in the active arm and two in placebo.

CONCLUSIONS

These results suggest that unopposed estrogen may be used safely by women with an intact uterus surviving a first myocardial infarction.

Has the short-term effect of black smoke exposure on pneumonia mortality been underestimated because hospitalisation is ignored: findings from a case-crossover study

BACKGROUND

Short-term associations have been demonstrated between air pollution and respiratory mortality including pneumonia. Studies typically estimate exposure based only on place of residence, yet many are in hospital prior to death. This study investigates lag length and tests the hypothesis that the effect of 'black smoke' is greater when restricted to pneumonia deaths in the community - Community Deaths from Pneumonia.

METHODS

A time-stratified case-crossover design using conditional logistic regression estimated the daily percentage increase in risk of pneumonia mortality in relation to 'black smoke' in the preceding 30 days. Cases were pneumonia deaths in Edinburgh 1981-1996. Multiple 'control' periods, were defined using the same weekdays for the same month as the case death. Lag structure was investigated by a stratified lag model with five 6-day periods and by distributed lag models. Hospital admissions data, defined a community death as someone who had not been in hospital in any of the 30 days before death.

RESULTS

Of 14,346 subjects who died from pneumonia, 7,536 were community deaths. Larger estimated increases in risks were seen in the community for all lag periods. Both stratified and distributed lag methods suggested positive effect estimates for 18 days after exposure and negative thereafter; the average percent increase per day across the 18 days was 0.70% (95% C.I. 0.29-1.14) for community subjects and 0.30% (95% C.I. 0.03-0.59) for all subjects.

CONCLUSIONS

Studies which fail to account for hospitalisation may underestimate exposure effects as stronger pollution effects on mortality were evident in community based subjects.

A comparison of population air pollution exposure estimation techniques with personal exposure estimates in a pregnant cohort

There is increasing evidence of the harmful effects for mother and fetus of maternal exposure to air pollutants. Most studies use large retrospective birth outcome datasets and make a best estimate of personal exposure (PE) during pregnancy periods. We compared estimates of personal NOx and NO2 exposure of pregnant women in the North West of England with exposure estimates derived using different modelling techniques. A cohort of 85 pregnant women was recruited from Manchester and Blackpool. Participants completed a time-activity log and questionnaire at 13-22 weeks gestation and were provided with personal Ogawa samplers to measure their NOx/NO2 exposure. PE was compared to monthly averages, the nearest stationary monitor to the participants' home, weighted average of the closest monitor to home and work location, proximity to major roads, as well as to background modelled concentrations (DEFRA), inverse distance weighting (IDW), ordinary kriging (OK), and a land use regression model with and without temporal adjustment. PE was most strongly correlated with monthly adjusted DEFRA (NO2r = 0.61, NOxr = 0.60), OK and IDW (NO2r = 0.60; NOxr = 0.62) concentrations. Correlations were stronger in Blackpool than in Manchester. Where there is evidence for high temporal variability in exposure, methods of exposure estimation which focus solely on spatial methods should be adjusted temporally, with an improvement in estimation expected to be better with increased temporal variability.

Applying optimal model selection in principal stratification for causal inference

Noncompliance to treatment allocation is a key source of complication for causal inference. Efficacy estimation is likely to be compounded by the presence of noncompliance in both treatment arms of clinical trials where the intention-to-treat estimate provides a biased estimator for the true causal estimate even under homogeneous treatment effects assumption. Principal stratification method has been developed to address such posttreatment complications. The present work extends a principal stratification method that adjusts for noncompliance in two-treatment arms trials by developing model selection for covariates predicting compliance to treatment in each arm. We apply the method to analyse data from the Esprit study, which was conducted to ascertain whether unopposed oestrogen (hormone replacement therapy) reduced the risk of further cardiac events in postmenopausal women who survive a first myocardial infarction. We adjust for noncompliance in both treatment arms under a Bayesian framework to produce causal risk ratio estimates for each principal stratum. For mild values of a sensitivity parameter and using separate predictors of compliance in each arm, principal stratification results suggested that compliance with hormone replacement therapy only would reduce the risk for death and myocardial reinfarction by about 47% and 25%, respectively, whereas compliance with either treatment would reduce the risk for death by 13% and reinfarction by 60% among the most compliant. However, the results were sensitive to the user-defined sensitivity parameter.

Assessing the impact of national level interventions on workplace respiratory disease in the UK: part 2--regulatory activity by the Health and Safety Executive

OBJECTIVE

To investigate whether interventions implemented by the UK Health and Safety Executive addressing exposure to isocyanate-based spray paints in motor vehicle repair (MVR), flour dust in craft bakeries, rosin-based solder flux fume (RBSFF) in the electronics industry, metalworking fluids and wood dust coincided with a decline in incidence of work-related short latency respiratory disease (SLRD) or asthma in the target groups.

METHOD

Changes in the incidence of SLRD reported to a UK-based surveillance scheme were compared using a longitudinal, negative binomial regression model with β distributed random effects. An interrupted time series design was used and comparisons according to inclusion or exclusion in the target group were made by including a statistical interactions expressed as a ratio of incidence rate ratios (RIRRs) in the model.

RESULTS

The incidence of SLRD attributed to flour dust significantly increased relative to all other agents (RIRR: 1.10; 95% CI 1.06 to 1.16) whereas SLRD attributed to RBSFF significantly declined relative to all other agents (0.94; 0.90 to 0.99). No significant changes in the incidence of SLRD attributed to wood dust (1.03; 0.91 to 1.16) or spray paints (1.03; 0.95 to 1.11) relative to all other agents were observed. A higher proportion of reports originated from the industries targeted by the intervention for RBSFF (65/107; 61%) than spray painting (27/93; 27%) or wood dust (16/42; 38%).

CONCLUSIONS

These data support a beneficial effect of interventions to reduce exposure to RBSFF but an increase in SLRD attributed to flour dust may indicate increased exposure or increased awareness of the problem.

Advanced maternal age and adverse pregnancy outcome: evidence from a large contemporary cohort

BACKGROUND

Recent decades have witnessed an increase in mean maternal age at childbirth in most high-resourced countries. Advanced maternal age has been associated with several adverse maternal and perinatal outcomes. Although there are many studies on this topic, data from large contemporary population-based cohorts that controls for demographic variables known to influence perinatal outcomes is limited.

METHODS

We performed a population-based cohort study using data on all singleton births in 2004-2008 from the North Western Perinatal Survey based at The University of Manchester, UK. We compared pregnancy outcomes in women aged 30-34, 35-39 and ≥40 years with women aged 20-29 years using log-linear binomial regression. Models were adjusted for parity, ethnicity, social deprivation score and body mass index.

RESULTS

The final study cohort consisted of 215,344 births; 122,307 mothers (54.19%) were aged 20-29 years, 62,371(27.63%) were aged 30-34 years, 33,966(15.05%) were aged 35-39 years and 7,066(3.13%) were aged ≥40 years. Women aged 40+ at delivery were at increased risk of stillbirth (RR = 1.83, [95% CI 1.37-2.43]), pre-term (RR = 1.25, [95% CI: 1.14-1.36]) and very pre-term birth (RR = 1.29, [95% CI:1.08-1.55]), Macrosomia (RR = 1.31, [95% CI: 1.12-1.54]), extremely large for gestational age (RR = 1.40, [95% CI: 1.25-1.58]) and Caesarean delivery (RR = 1.83, [95% CI: 1.77-1.90]).

CONCLUSIONS

Advanced maternal age is associated with a range of adverse pregnancy outcomes. These risks are independent of parity and remain after adjusting for the ameliorating effects of higher socioeconomic status. The data from this large contemporary cohort will be of interest to healthcare providers and women and will facilitate evidence based counselling of older expectant mothers.

Time trends in the incidence of work-related mental ill-health and musculoskeletal disorders in the UK

OBJECTIVES

To determine UK trends (from 1996 to 2009) in incidence of work-related mental ill-health and musculoskeletal disorders, for all industry as well as for health and social care employees. Second, to investigate whether there may have been a recent shift from a physical to psychological perspective in how patients present their illness by comparing reporting trends for back pain and 'other work stress'.

METHODS

Multilevel models were used to investigate changes in incidence of work-related illness, as diagnosed by specialist physicians. The dependent variable comprised case reports to The Health and Occupation Research network. Comparisons were made between medical specialties, industry (health and social care vs all other employees), gender and diagnosis.

RESULTS

Trends for Occupational Physicians' (OP) reporting mental ill-health (average annual increase +3.7% (95% CI +2.2% to +5.2%)) differed significantly (p<0.001) from psychiatrists' reporting over the same time period (-5.9% (95% CI -7.6% to -4.2%)). For OPs' reporting, the rate of increase was greater for females and for health and social care employees. A fall in incidence of musculoskeletal disorders for OPs of -5.8% (95% CI -7.3% to -4.3%) and rheumatologists' reporting -6.6% (95% CI -8.3% to -4.8%) was found, with little variation by gender or industry. Within health and social care, an increase in incidence of 'other work stress' was accompanied by a similar decrease in 'spine/back pain'.

CONCLUSIONS

The evidence presented is consistent with a shift in the presentation of ill-health from a physical to psychological perspective, although changes in hazards, prevention measures and physician awareness should also be considered as explanations.

Increased risk of miscarriage and ectopic pregnancy among women with irritable bowel syndrome

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is the most commonly diagnosed gastrointestinal condition and is most prevalent in women of reproductive age. We investigated the effects of IBS on risk for adverse outcomes from pregnancy.

METHODS

We conducted a cohort study by using the United Kingdom General Practice Research Database. The study cohort consisted of 100,000 women selected by stratified random sampling from all women with a diagnosis of pregnancy from January 1, 1990, to December 31, 2008. Those with a recorded diagnosis of IBS before pregnancy were identified (n = 26,543). Outcome measures were spontaneous miscarriage, ectopic pregnancy, preeclampsia, and stillbirth. Odds ratios (ORs) and 95% confidence intervals (CIs) for the association between IBS and pregnancy outcomes were estimated by using logistic regression adjusted for several potential confounders.

RESULTS

Of women diagnosed with IBS before pregnancy, 6578 (7%) had a spontaneous miscarriage, 741 (0.74%) had an ectopic pregnancy, 425 (0.43%) developed preeclampsia, and 217 (0.22%) had a stillbirth. Maternal IBS was associated with a moderately increased risk of miscarriage (OR, 1.21; 95% CI, 1.13-1.30) and ectopic pregnancy (OR, 1.28%; 95% CI, 1.06-1.55). There did not appear to be an association between IBS and preeclampsia (OR, 1.09; 95% CI, 0.85-1.39) or stillbirth (OR, 1.00; 95% CI, 0.69-1.44).

CONCLUSIONS

IBS, a common disorder in women of reproductive age, appears to increase the risk of miscarriage and ectopic pregnancy. These findings indicate the importance of prenatal care for women with IBS.

Modifiable and non-modifiable risk factors for poor semen quality: a case-referent study

STUDY QUESTION

Are common lifestyle factors associated with low-motile sperm concentration (MSC)?

SUMMARY ANSWER

Common lifestyle choices make little contribution to the risk of low MSC.

WHAT IS KNOWN AND WHAT THIS PAPER ADDS

Reviews of male subfertility often highlight how aspects of men's adult lifestyle can significantly increase their risk of subfertility but the strength of supporting evidence is weak. In this study, although low MSC was associated with a history of testicular surgery, being in manual work, not wearing loose underwear and black ethnicity, no relation was found to consumption of alcohol, use of tobacco or recreational drugs or high body mass index (BMI). These results suggest that delaying assisted conception to make changes to lifestyle is unlikely to enhance conception.

DESIGN

Unmatched case-referent study with 939 cases and 1310 referents. Cases had a low-MSC relative to the time since last ejaculation (<12 × 10(6) for 3 days of abstinence). Exposures included self-reported exposures to alcohol, tobacco, recreational drugs as well as occupational and other factors.

PARTICIPANTS AND SETTING

Eligible men, aged 18 or above, were part of a couple who had been attempting conception without success following at least 12 months of unprotected intercourse and also had no knowledge of any semen analysis. They were recruited from 14 fertility clinics across the UK during a 37-month period from 1 January 1999.

MAIN RESULTS AND THE ROLE OF CHANCE

Risk factors for low MSC, after adjustment for centre and confounding factors, included a history of testicular surgery [odds ratio = 2.39, 95% confidence interval (CI): 1.75, 3.28], being in manual work [odds ratio (OR) = 1.28, 95% CI: 1.07, 1.53] or not working (OR = 1.78, 95% CI: 1.22, 2.59) and having black ethnicity (OR = 1.99, 95% CI: 1.10, 3.63). Conversely, men who wore boxer shorts (OR = 0.76, 95% CI: 0.64, 0.92) or who had a previous conception (OR = 0.71, 95% CI: 0.60, 0.85) were less likely to be a case. No significant association was found with smoking and alcohol consumption, the use of recreational drugs, a high BMI or having a history of mumps or fever.

BIAS, CONFOUNDING AND OTHER REASONS FOR CAUTION

Data were collected blind to outcome, and exposure information should not have been subject to reporting bias. Among men attending the various clinics less than half met the study eligibility criteria and among those who did, two out of five were not recruited. It is not known whether any of those who refused to take part did so because they had a lifestyle they did not want subjected to investigation. Although the power of the study was sufficient to draw conclusions about common lifestyle choices, it cannot comment on exposures that are perhaps rare and poorly reported: the finding that use of street drugs was unrelated to low MSC cannot be assumed to apply to all such drugs and all patterns of use. The case definition did not consider sperm morphology or sperm DNA integrity.

GENERALIZABILITY TO OTHER POPULATIONS

All participating clinics saw patients at no cost (under the UK National Health Service) and the study population may differ from those in countries without such provision. Even within the UK, low-income couples may choose not to undertake any investigation believing that they would subsequently be unable to afford treatment.

Work-related asthma in France: recent trends for the period 2001-2009

OBJECTIVE

Knowledge on the time-course (trends) of work-related asthma (WRA) remains sparse. The aim of this study was to describe WRA trends in terms of industrial activities and the main causal agents in France over the period 2001-2009.

METHOD

Data were collected from the French national network of occupational health surveillance and prevention (Réseau National de Vigilance et de Prévention des Pathologies Professionnelles (RNV3P)). Several statistical models (non-parametric test, zero-inflated negative binomial, logistic regression and time-series models) were used and compared with assess trends.

RESULTS

Over the study period, 2914 WRA cases were included in the network. A significant decrease was observed overall and for some agents such as isocyanates (p = 0.007), aldehydes (p = 0.01) and latex (p = 0.01). Conversely, a significant increase was observed for cases related to exposure to quaternary ammonium compounds (p = 0.003). The health and social sector demonstrated both a growing number of cases related to the use of quaternary ammonium compounds and a decrease of cases related to aldehyde and latex exposure.

CONCLUSIONS

WRA declined in France over the study period. The only significant increase concerned WRA related to exposure to quaternary ammonium compounds. Zero-inflated negative binomial and logistic regression models appear to describe adequately these data.

Occupation and work-related ill-health in UK construction workers

BACKGROUND

Construction workers are at increased risk of work-related ill-health (WRI) worldwide.

AIMS

To compare the incidence of medically reported WRI in occupations within the UK construction industry according to job title.

METHODS

We calculated standardized incidence rate ratios (SRRs) using WRI cases for individual job titles returned to The Health and Occupation Reporting network by clinical specialists and UK population denominators. We counted frequencies of reported causal exposures or tasks reported by clinical specialists, occupational physicians and general practitioners.

RESULTS

We found significantly increased incidence of WRI compared with other workers in the same major Standard Occupational Classification, i.e. workers with similar levels of qualifications, training, skills and experience, for skin neoplasia in roofers (SRR 6.3; 95% CI: 3.1-13.1), painters and decorators (2.1; 95% CI: 1.2-3.6) and labourers in building and woodworking trades (labourers, 6.6; 95% CI: 3.2-13.2); contact dermatitis in metal workers (1.4; 95% CI: 1.1-1.7) and labourers (1.6; 95% CI: 1.1-2.3); asthma in welders (3.8; 95% CI: 2.8-5.0); musculoskeletal disorders in welders (1.7; 95% CI: 1.1-2.8), road construction operatives (6.1; 95% CI: 3.8-9.6) and labourers (2.5; 95% CI: 1.7-3.7); long latency respiratory disease (mesothelioma, pneumoconiosis, lung cancer, non-malignant pleural disease) in pipe fitters (4.5; 95% CI: 3.2-6.2), electrical workers (2.7; 95% CI: 2.4-3.2), plumbing and heating engineers (2.3; 95% CI: 1.9-2.7), carpenters and joiners (2.7; 95% CI: 2.3-3.1), scaffolders (12; 95% CI: 8-18) and labourers (3.3; 95% CI: 2.6-4.1).

CONCLUSIONS

UK construction industry workers have significantly increased risk of WRI. These data in individual construction occupations can be used to inform appropriate targeting of occupational health resources.

Improving estimates of specialist-diagnosed, work-related respiratory and skin disease

BACKGROUND

Work-related skin and respiratory disease still constitute an important part of the work-related ill-health (WRIH) burden of Great Britain (GB). It is therefore important to be able to accurately quantify the true incidence of these two groups of disease.

AIMS

To improve the accuracy of the methodology to estimate clinical specialist incidence rates, with a focus on skin and respiratory disease. Specifically, we sought to estimate the number of additional cases not captured by voluntary surveillance through The Health and Occupation Reporting (THOR) network and provide a better estimation of the true incidence of work-related skin and respiratory disease in GB.

METHODS

Cases not captured by THOR in 2005-2007 due to non-participation of eligible clinical specialists and due to <100% response rates by THOR participants were estimated, and the numerator adjusted accordingly. Adjusted incidence rates were calculated using Labour Force Survey data as the denominator.

RESULTS

During 2005-2007, 62% of skin cases and 60% of GB respiratory cases were likely to have been captured by THOR. After adjustment, dermatologist-derived incidence rates for skin disease were raised from 9 to 14 per 100,000 employed, while those for respiratory disease were raised from 10 to 17 per 100,000 employed.

CONCLUSIONS

We have provided a significant improvement in the surveillance-based methodology used to estimate the number of cases of WRIH captured by THOR and hence enabled more accurate estimations of GB incidence rates for clinical specialist-reported WRIH.

Performance of statistical methods for analysing survival data in the presence of non-random compliance

Noncompliance often complicates estimation of treatment efficacy from randomized trials. Under random noncompliance, per protocol analyses or even simple regression adjustments for noncompliance, could be adequate for causal inference, but special methods are needed when noncompliance is related to risk. For survival data, Robins and Tsiatis introduced the semi-parametric structural Causal Accelerated Life Model (CALM) which allows time-dependent departures from randomized treatment in either arm and relates each observed event time to a potential event time that would have been observed if the control treatment had been given throughout the trial. Alternatively, Loeys and Goetghebeur developed a structural Proportional Hazards (C-Prophet) model for when there is all-or-nothing noncompliance in the treatment arm only. Whitebiet al. proposed a 'complier average causal effect' method for Proportional Hazards estimation which allows time-dependent departures from randomized treatment in the active arm. A time-invariant version of this estimator (CHARM) consists of a simple adjustment to the Intention-to-Treat hazard ratio estimate. We used simulation studies mimicking a randomized controlled trial of active treatment versus control with censored time-to-event data, and under both random and non-random time-dependent noncompliance, to evaluate performance of these methods in terms of 95 per cent confidence interval coverage, bias and root mean square errors (RMSE). All methods performed well in terms of bias, even the C-Prophet used after treating time-varying compliance as all-or-nothing. Coverage of the latter method, as implemented in Stata, was too low. The CALM method performed best in terms of bias and coverage but had the largest RMSE.

The incidence of medically reported work-related ill health in the UK construction industry

OBJECTIVE

Self-reported work-related ill health (SWI) data show a high incidence of occupational ill health and a high burden of cancer attributable to occupational factors in the UK construction industry. However, there is little information on the incidence of medically reported work-related ill health (WRI) within this industry. This study aims to examine the incidence of WRI within the UK construction industry.

METHOD

Standardised incidence rate ratios (SRRs) were used to compare incidence rates of reports of medically certified work-related ill health returned to The Health and Occupation Reporting network (THOR) within the UK construction industry with all other UK industries combined.

RESULTS

Male UK construction industry workers aged under 65 years had significantly raised SRRs for respiratory (3.8, 95% CI 3.5 to 4.2), skin (1.6, 1.4 to 1.8) and musculoskeletal disorders (MSD; 1.9, 1.6 to 2.2). These SRRs were further raised for those working within a construction trade. The increased SRRs for skin disease within male construction industry workers were due to contact dermatitis (1.4, 1.2 to 1.6) and neoplasia (4.2, 3.3 to 5.3). For respiratory disease, the increased SRRs were due to non-malignant pleural disease (7.1, 6.3 to 8.1), mesothelioma (7.1, 6.0 to 8.3), lung cancer (5.4, 3.2 to 8.9) and pneumoconiosis (5.5, 3.7 to 8.0), but the SRRs for asthma (0.09, 0.06 to 0.11) and mental ill health (0.3, 0.1 to 0.4) were significantly reduced.

CONCLUSION

The significantly raised SRRs for medically reported MSD and significantly reduced SRRs for mental ill health in construction workers confirm self-reported UK data. These SRRs provide a baseline of the incidence of WRI in the UK construction industry from which to monitor the effects of changes in policy or exposures.

Undiagnosed coeliac disease in a father does not influence birthweight and preterm birth

There is conflicting evidence regarding the effect of coeliac disease (CD) in the father on birthweight and preterm birth. We investigated the association between paternal CD and birthweight and preterm birth. Medical records of all singleton live-born children in Denmark between 1 January 1979 and 31 December 2004 were linked to information about parents' diseases. Fathers who were diagnosed with CD were then identified. Fathers with CD were considered treated if they were diagnosed before pregnancy and untreated if they were diagnosed after the date of conception. The outcome measures were: birthweight, small-for-gestational age (birthweight<10th centile for gestational age) and preterm birth (<37 weeks). We compared the offspring of men without CD (n = 1 472 352) and offspring of those with CD [untreated (n = 138) and treated (n = 473)]. There was no significant association between untreated CD in the father and birthweight (adjusted mean difference = -3 g; [95% CI -46, 40]) or preterm birth (adjusted odds ratio (OR) = 0.86, [95% CI 0.53, 1.37]) (compared with no CD). There was some evidence for an association between treated paternal CD and birthweight (adjusted mean difference = -81 g; [95% CI -161, -3]), but not preterm birth (adjusted OR = 1.76, [95% CI 0.95, 3.26]). Untreated paternal CD was not associated with an increased risk of reduced birthweight, or of preterm birth. There was some evidence that diagnosis and presumed treatment of paternal CD with a gluten-free diet is associated with reduced birthweight.

Medically reported work-related ill-health in the UK agricultural sector

BACKGROUND

Self-reported work-related ill-health (WRI) statistics suggest that agricultural workers in the UK are at an increased risk of musculoskeletal disorders (MSD), skin and respiratory disease. However, there is little comprehensive medically reported information on WRI in the UK agricultural sector.

METHODS

Cases of WRI within the UK from 2002 to 2008, as reported to The Health and Occupation Reporting (THOR) network by occupational physicians, clinical specialists and general practitioners, were analysed. Directly standardized incidence rate ratios (SRRs) for the agricultural sector versus all other sectors were calculated for dermatological, musculoskeletal, respiratory and psychological illness, using as the standard population the UK working population as estimated from the Labour Force Survey.

RESULTS

During 2002-08, 471 cases within the agricultural sector were reported to THOR (2% of all cases). Based on reports by clinical specialists, male agricultural workers aged <65 years had significantly raised SRRs for MSD (2.3, 95% CI 1.6-3.3), allergic alveolitis (32, 95% CI 19-51), asthma (1.9, 95% CI 1.2-3.0) and skin neoplasia (7.9, 95% CI 5.8-10.9) and a significantly reduced SRR for asbestos-related respiratory disease (0.4, 95% CI 0.2-0.7). Reports of mental ill-health in agricultural workers were low.

CONCLUSIONS

These medically reported incidence data provide information on WRI in the UK agricultural sector. Consistent with other sources, there are increased risks for asthma, allergic alveolitis and MSD and a reduced risk for mental ill-health. The raised incidence of skin cancer requires confirmation and further comparison with reliable estimates of the incidence in the UK workforce.

Intention to treat, per protocol, as treated and instrumental variable estimators given non-compliance and effect heterogeneity

We consider the behaviour of three approaches to efficacy estimation--using so-called 'as treated' (AT), 'per protocol' (PP) and 'instrumental variable' (IV) analyses--and of the Intention to Treat estimator, in a two-arm randomized treatment trial with a Normally distributed outcome when there is treatment effect heterogeneity and non-random compliance with assigned treatment. Formulae are derived for the bias of estimators when used either to estimate average treatment effect (ACE) or to estimate complier average treatment effect (CACE) under several models for the relationship between compliance and potential outcomes. These enable the expected values of AT, PP and IV estimators to be ranked in relation to ACE, and show that AT and PP estimators are generally biased for both ACE and CACE even under homogeneity. However, we show that the difference between any pair of (AT, PP, IV) estimates can be used to estimate the correlation between the latent variable determining compliance behaviour and one potential outcome. In the absence of measures that predict compliance, bounds for ACE can only be set given strong assumptions. Regarding the Intention to Treat estimator, while this is 'biased towards the null' if viewed as a measure of CACE, we show that it is not always so in relation to ACE. Finally we discuss the behaviour of the estimators under weak and strong null hypotheses.

The impact of maternal celiac disease on birthweight and preterm birth: a Danish population-based cohort study

BACKGROUND

Adverse pregnancy outcomes have been associated with maternal celiac disease (CD). In this study, we investigate the effect of treated and untreated maternal CD on infant birthweight and preterm birth.

METHODS

A population-based cohort study consisted of all singleton live births in Denmark between 1 January 1979 and 31 December 2004 was used. A total of 1,504,342 babies were born to 836,241 mothers during the study period. Of those, 1105 babies were born to women with diagnosed CD and 346 were born to women with undiagnosed CD. Women with diagnosed CD were considered as treated with a gluten free diet while women with undiagnosed CD were considered as untreated. The outcome measures were: birthweight, small for gestational age (SGA: birthweight <10th centile), very small for gestational age (VSGA: birthweight <5th centile) and preterm birth. We compared these measures in treated and untreated women with those of a reference group (no history of CD).

RESULTS

Women with untreated CD delivered smaller babies [difference = -98 g (95% CI: -130, -67)], with a higher risk of SGA infants [OR = 1.31 (95% CI: 1.06, 1.63)], VSGA infants [OR = 1.54 (95% CI: 1.17, 2.03)] and preterm birth [OR = 1.33 (95% CI: 1.02, 1.72)] compared with women without CD. Women with treated CD had no increased risk of reduced mean birthweight, risk of delivering SGA and VSGA infants or preterm birth compared with women without CD.

CONCLUSION

Untreated maternal CD increases the risk of reduced birthweight, the risk of delivering SGA and VSGA infants and preterm birth. Diagnosis and presumed treatment of maternal CD with a gluten-free diet appeared to result in a birthweight and preterm birth rate similar to those in women without CD.

Agreement in diagnosing occupational asthma by occupational and respiratory physicians who report to surveillance schemes for work-related ill-health

OBJECTIVES

To assess diagnostic agreement for occupational asthma, and to identify case and rater characteristics associated with this diagnosis.

METHODS

Summaries of possible occupational asthma cases were sent to 104 occupational and respiratory physicians. Raters assigned likelihood scores (0-100%) of occupational asthma based on case histories (phase 1), and on histories plus investigative procedures (phase 2). Interclass correlation coefficients were calculated as statistical measures of reliability for occupational asthma scores. Comparisons between mean scores were assessed for statistical significance using tests based on multilevel models. RRs were calculated to summarise effects of raters' demographics, and of supplying investigative procedures information.

RESULTS

Occupational asthma scores showed limited agreement within each group of (occupational or respiratory) physicians, but scores were not systematically different. The difference between mean overall scores was 2.1% (52.1% occupational physicians; 50.0% respiratory physicians) in phase 1 (95% CI -2.6 to 6.8, p=0.37). In phase 2, mean overall scores were 46.1% (occupational physicians) and 41.5% (respiratory physicians); the difference in mean overall scores was 4.6% (95% CI -3.5 to 12.5, p=0.27). Raters with General Medical Council registration > or =1986 were more likely to give a positive occupational asthma diagnosis. In phase 2, male raters were more likely to label cases as occupational asthma than female raters (RR 4.5, 95% CI 3.3 to 6.0).

CONCLUSIONS

The RR of a positive occupational asthma diagnosis was unaffected by clinical specialty. Further work on why physicians consider cases to be occupational asthma will assist better diagnosis and prevention of this disease.

Sex ratio at birth following prenatal maternal exposure to severe life events: a population-based cohort study

BACKGROUND

A reduction in the sex ratio at birth has been linked to maternal condition during and before pregnancy. A recent study reported an association between maternal exposure to severe life events and sex ratio at birth using the Danish national register. We attempted to replicate that study using a new Danish cohort.

METHODS

Mothers of all singleton live births (n = 1.35 million births) in Denmark, between 1 January 1980 and 31 December 2002, were linked to data on their children and partners. The old cohort consisted of babies born between 1980 and 1992 (n = 699 362), whereas the new cohort consisted of babies born between 1993 and 2002 (n = 633 451). We defined exposure as death or serious illness in older children and partners in the first trimester or in the 6 months before conception. Sex ratio at birth was defined as the proportion of male live births.

RESULTS

During the study period, there were 1,349,099 singleton live births (692,870 boys and 656,229 girls). The sex ratio at birth in the new cohort was 0.5134. In the new cohort, prenatal exposure to severe life events was not associated with a reduction in the sex ratio at birth [relative risk = 1.00 (95% confidence interval: 0.95-1.05)].

CONCLUSIONS

In the new cohort, we did not find strong evidence that, in a stable western population, prenatal exposure to severe life events is associated with a reduction in the sex ratio at birth.

The validity and reliability of diagnoses of work-related mental ill-health

OBJECTIVES

To establish the reliability and validity of work-related mental ill-health diagnoses.

BACKGROUND

A UK-based surveillance scheme for work-related ill-health involving occupational physicians (OPs) reporting suggests that mental ill-health incidence is increasing by around 13% per year, with anxiety, depression and "other work-related stress" being the most common diagnoses. There have been no studies of the validity and reliability of such diagnoses. Given the existence of a large network of psychiatrists (PSYs) also involved in surveillance of work-related ill-health, an opportunity arose to measure the concurrent validity and reliability of work-related mental ill-health diagnoses.

METHODS

100 anonymised summaries of cases previously reported by OPs or PSYs were collected; each was sent to 5 PSYs and 5 OPs, who assigned a diagnosis and judged whether the case was work-related. Concurrent validity of the ill-health aspect of the diagnoses, and of the opinion as to work-relatedness, was assessed by comparing the overall classifications of cases by OPs and PSYs. Reliability of the diagnostic classification was measured by kappa matrices.

RESULTS

Diagnostic proportions for PSYs and OPs demonstrated good agreement for anxiety, depression, anxiety plus depression and "stress" (11%, 34%, 27%, 14%) and (14%, 30%, 27%, 17%), respectively. In both groups, kappa coefficients were high for a psychotic diagnosis (0.78, 95% CI: 0.74 to 0.83), but not as high for anxiety (0.27, 95% CI: 0.23 to 0.32), depression (0.34, 95% CI: 0.29 to 0.38) and "stress" (0.15, 95% CI: 0.10 to 0.19). The odds ratio of classifying a case as work-related among PSYs compared to OPs was 2.39 (95% CI: 1.68 to 3.38), p<0.001.

CONCLUSIONS

The overall agreement between OPs and PSYs on mental ill-health diagnoses suggests that OP diagnoses are valid for epidemiological purposes. However, the within-group reliability of the diagnosis "stress" is low. Given differences in judgements about work-relatedness, further research is needed to investigate this aspect of a diagnosis.