A nationwide follow-up study of occupational organic dust exposure and risk of chronic obstructive pulmonary disease (COPD).

OBJECTIVES: To study exposure-response relations between cumulative organic dust exposure and incident chronic obstructive pulmonary disease (COPD) among subjects employed in the Danish farming and wood industry. METHODS: We studied exposure-response relations between cumulative organic dust exposure and incident COPD (1997-2013) among individuals born during 1950-1977 in Denmark ever employed in the farming or wood industry (n=1 75 409). Industry-specific employment history (1964-2007), combined with time-dependent farming and wood industry-specific exposure matrices defined cumulative exposure. We used logistic regression analysis with discrete survival function adjusting for age, sex and calendar year. Adjustment for smoking status was explored in a subgroup of 4023 with smoking information available. RESULTS: Cumulative organic dust exposure was inversely associated with COPD (adjusted rate ratios (RRadj (95% CIs) of 0.90 (0.82 to 0.99), 0.76 (0.69 to 0.84) and 0.52 (0.47 to 0.58) for intermediate-low, intermediate-high and high exposure quartiles, respectively, compared with the lowest exposure quartile). Lagging exposure 10 years was not consistently suggestive of an association between cumulative exposure and COPD; RRadj (95% CI): 1.05 (0.94 to 1.16), 0.92 (0.83 to 1.02) and 0.63 (0.56 to 0.70). Additional stratification by duration of employment showed no clear association between organic dust exposure and COPD except for the longer exposed (15-40 years) where an inverse association was indicated. Subgroup analyses showed that smoking had no impact on exposure-response estimates. CONCLUSIONS: Our findings show no increased risk of COPD with increasing occupational exposure to organic dust in the farming or wood industry. Potential residual confounding by smoking can, however, not be ruled out.

Testing the association between psychosocial job strain and adverse birth outcomes--design and methods.

BACKGROUND: A number of studies have examined the effects of prenatal exposure to stress on birth outcomes but few have specifically focused on psychosocial job strain. In the present protocol, we aim to examine if work characterised by high demands and low control, during pregnancy, is associated with the risk of giving birth to a child born preterm or small for gestational age. METHODS AND DESIGN: We will use the Danish National Birth Cohort where 100.000 children are included at baseline. In the present study 49,340 pregnancies will be included. Multinomial logistic regression will be applied to estimate odds ratios for the outcomes: preterm; full term but small for gestational age; full term but large for gestational age, as a function of job-strain (high strain, active and passive versus low strain). In the analysis we control for maternal age, Body Mass Index, parity, exercise, smoking, alcohol use, coffee consumption, type of work (manual versus non-manual), maternal serious disease and parents' heights as well as gestational age at interview. DISCUSSION: The prospective nature of the design and the high number of participants strengthen the study. The large statistical power allows for interpretable results regardless of whether or not the hypotheses are confirmed. This is, however, not a controlled study since all kinds of 'natural' interventions takes place throughout pregnancy (e.g. work absence, medical treatment and job-redesign). The analysis will be performed from a public health perspective. From this perspective, we are not primarily interested in the effect of job strain per se but if there is residual effect of job strain after naturally occurring preventive measures have been taken.

A comparison of conventional and computer-assisted semen analysis (CRISMAS software) using samples from 166 young Danish men.

The aim of the present study was to compare assessments of sperm concentration and sperm motility analysed by conventional semen analysis with those obtained by computer-assisted semen analysis (CASA) (Copenhagen Rigshospitalet Image House Sperm Motility Analysis System (CRISMAS) 4.6 software) using semen samples from 166 young Danish men. The CRISMAS software identifies sperm concentration and classifies spermatozoa into three motility categories. To enable comparison of the two methods, the four motility stages obtained by conventional semen analysis were, based on their velocity classifications, divided into three stages, comparable to the three CRISMAS motility categories: rapidly progressive (A), slowly progressive (B) and non-progressive (C+D). Differences between the two methods were large for all investigated parameters (P < 0.001). CRISMAS overestimated sperm concentration and the proportion of rapidly progressive spermatozoa and, consequently, underestimated the percentages of slowly progressive and non-progressive spermatozoa, compared to the conventional method. To investigate whether results drifted according to time of semen analysis, results were pooled into quarters according to date of semen analysis. CRISMAS motility results appeared more stable over time compared to the conventional analysis; however, neither method showed any trends. Apparently, CRISMAS CASA results and results from the conventional method were not comparable with respect to sperm concentration and motility analysis. This needs to be accounted for in clinics using this software and in studies of determinants of these semen characteristics.

Fetal loss and maternal serum levels of 2,2',4,4',5,5'-hexachlorbiphenyl (CB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) exposure: a cohort study in Greenland and two European populations.

BACKGROUND: In the present study, the aim is to examine the risk of fetal loss related to environmental 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) or 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) exposure. METHODS: We related LC/MS/MS measurements of CB-153 and p,p'-DDE in serum samples to interview-data on previous fetal loss in populations of pregnant women from Poland, Ukraine and Greenland. RESULTS: In total, 1710 women were interviewed, and 678 of these had at least one previous pregnancy. The risk of ever experiencing a fetal loss increased at higher levels of CB-153 and p,p'-DDE exposure, with an adjusted odds ratio (OR) of 2.4; confidence interval (CI) (1.1-5.5) for CB-153>200 ng/g lipid compared to 0-25 ng CB-153/g lipid and OR of 2.5 CI (0.9-6.6) for p,p'-DDE>1500 ng/g lipid compared to 0-250 ng DDE/g lipid. However, no clear dose response associations were observed. The results further suggest that high level of organochlorine serum concentrations may be related to repeated loss. CONCLUSIONS: The risk of fetal loss may increase at higher levels of CB-153 and p,p'-DDE exposure, although lack of dose response and inconsistencies between countries did not allow for firm conclusions.

Maternal use of oral contraceptives and risk of fetal death.

Intrauterine exposure to artificial sex hormones such as oral contraceptives may be associated with an increased risk of fetal death. Between 1996 and 2002, a total of 92 719 women were recruited to The Danish National Birth Cohort and interviewed about exposures during pregnancy. Outcome of pregnancy was identified through linkage to the Civil Registration System and the National Discharge Registry. The authors analysed the risk of fetal death after recruitment to the cohort by using proportional hazards regression models with gestational age as the underlying time scale. In total, 1102 (1.2%) women took oral contraceptives during pregnancy. Use of combined oestrogen and progesterone oral contraceptives (COC) or progesterone-only oral contraceptives (POC) during pregnancy was not associated with increased hazard ratios of fetal death compared with non-users, HR 1.01 [95% CI 0.71, 1.45] and HR 1.37 [95% CI 0.65, 2.89] respectively. Neither use of COC nor POC prior to pregnancy was associated with fetal death. Stratification by maternal age and smoking showed elevated risks of fetal death for women <30 years and smokers using oral contraception during pregnancy, but the interactions were not significant. In conclusion, there was no evidence that oral contraceptive use before or during pregnancy is associated with an increased risk of fetal death.

Secondary healthcare contacts after multiphasic preventive health screening: a randomized trial.

AIM: To analyze the consequence of preventive health screenings and discussions on the utilization of secondary healthcare. METHODS: All 30- to 49-year-old residents registered with a general practitioner in the district of Ebeltoft, Denmark, were included (n = 3,464) in a randomized controlled trial with eight years' follow-up. A random sample of 2,030 subjects was selected for invitation (Invited). The remaining 1,434 persons were never contacted and served as external control group (Non-Invited). Persons accepting participation were randomly divided into one internal control group (Questionnaire) and two intervention groups. One intervention group was offered three health screenings (Health Screening) during the five years. The other intervention group were in addition offered a yearly health discussion with their general practitioner (Health Screening and Discussion). RESULTS: The rate ratio for hospital admissions was 0.97 (95% confidence interval 0.80 to 1.18) in the Invited group compared with the Non-Invited. The annual admission rates showed a significant trend (p = 0.0003) with a decrease four and five years after intervention launch for the Invited group compared with the Non-Invited. A similar trend was found when comparing the internal control group with intervention groups (p = 0.0016). CONCLUSIONS: A 30- to 49-year-old general population's utilization of secondary healthcare did not increase in response to a general health promotion offer. During the observation period a significant decline in annual hospital admission rates was seen.

Semen quality and exposure to persistent organochlorine pollutants.

BACKGROUND: Inconsistent results have been found in previous human studies on male reproductive toxicity of persistent organochlorine pollutants. The majority of studies have been conducted among selected populations of infertility clients or among occupational cohorts including a limited number of participants. METHODS: We conducted a cross-sectional study of semen quality and serum concentration of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE) among 763 men. We included men from all regions in Greenland (n = 194), fishermen from Sweden (n = 185), inhabitants of the city of Kharkiv, Ukraine (n = 195), and inhabitants of the city of Warsaw, Poland (n = 189). Blood samples were analyzed for CB-153 and p,p'-DDE using gas chromatography-mass spectrometry and adjusted for serum lipids. RESULTS: Sperm concentration was not impaired with increasing serum CB-153 or p,p'-DDE levels in any of the separate groups or overall. Similarly, the proportion of morphologically normal sperm was not associated with either CB-153 or p,p'-DDE blood concentration. However, sperm motility was inversely related to CB-153 concentration in Greenland and the Swedish fishermen population. Across all 4 regions, the sperm motility decreased on average by 3.6% (95% confidence interval = 1.7% to 5.6%) per one-unit increase in the log of blood CB-153 (ng/g lipid). The concentration of p,p'-DDE was negatively associated with sperm motility in the Greenlandic population and in the compiled dataset. CONCLUSION: Adult exposure to persistent organochlorine pollutants within the ranges observed in the present study is not likely to cause reduction in sperm concentration or morphology. However, higher exposure may be associated with impaired sperm motility.