Influence of errors in job codes on job exposure matrix-based exposure assessment in the register-based occupational cohort DOC*X.

Objective Job-exposure matrices (JEM) may be efficient for exposure assessment in occupational epidemiological studies, but they rely on valid job information. We evaluated the agreement between JEM-based exposure estimates according to self-reported job titles converted to DISCO-88 codes and according to register-based DISCO-88 codes in the Danish Occupational Cohort with eXposure data (DOC*X). Furthermore, we evaluated the agreement between these two sets of DISCO-88 codes. Methods We used JEM regarding wood dust, lifting, standing/walking, arm elevation >90°, and noise from DOC*X. Participants from previous questionnaire studies were assigned JEM-based exposure estimates using (i) self-reported job titles converted to DISCO-88 codes and (ii) DISCO-88 codes registered in DOC*X, in four time periods (1976-78: N=7707; 1981-83: N=2193; 1991-94: N=2664; 2004: N=11 782). Agreement between the exposure estimates and between the DISCO-88 codes (four-digit levels, 1-4) was evaluated by kappa (κ) statistics. Sensitivities were calculated using the self-reported observation as the gold standard. Results We found substantial agreement (κ>0.60) between exposure estimates for all types of job-exposures and all time periods except for one κ. Low sensitivity (30-65%) was found for the period 1981-83, but for the other time periods the sensitivities varied between 60-91%. For individual 4-digit DISCO-88 codes, the sensitivities varied substantially and overall the sensitivities increased by lower digit level of DISCO-88. Conclusion The validity of the DISCO-88 codes in DOC*X was generally high. Substantial agreement was found for the JEM-based exposure estimates and the DISCO-88 codes per se, although the DISCO-88 code-specific agreement varied across digit levels and time periods.

Acute myocardial infarction in relation to physical activities at work: a nationwide follow-up study based on job-exposure matrices.

Objective This study aimed to evaluate sex-specific risks of acute myocardial infarction (AMI) according to lifting and standing/walking at work. Methods The study population included 1.15 million Danish wage earners. Annual job codes from 1976 onwards were linked to specific exposures using job-exposure matrices (JEM). Cases of AMI during follow-up 1996-2016 were retrieved from national registers. Incidence rate ratios (IRR) were computed by Poisson regression adjusting for demographic and JEM-assessed lifestyle factors. Models addressed physical activities at work the previous 0-2 years (short-term risk) and cumulative physical activities (long-term risk). Results During 21.4 million person-years of follow-up, 22 037 AMI occurred in men and 6942 in women. Exposure-response relationships between recent physical activities at work and AMI were not evident. In men, the fully adjusted long-term IRR for the highest of five exposure categories compared to the lowest were 1.09 [95% confidence interval (CI) 1.03-1.15] for lifting and 1.01 (95% CI 0.96-1.07) for standing/walking. In women, the corresponding figures were 1.27 (95% CI 1.15-1.40) and 1.18 (95% CI 1.07-1.30). The latter risk estimate was strongly attenuated, and the trend became insignificant when adjusted for lifting. Findings were only partially supported by sensitivity analyses. Conclusion The study provides limited support to the hypothesis that long-term lifting and standing/walking at work is related to increased risk of AMI. Possible effects of acute physical exertion are not addressed and bias towards the null because of crude exposure assignment cannot be ruled out.

Salivary cortisol and sleep problems among civil servants.

OBJECTIVE: The present study used information from a field study conducted among 4489 civil servants (70% women) in Denmark in 2007. The purpose was to examine the association between sleep problems and salivary cortisol by using a cross-sectional design with repeated measures in a subsample three-month later. METHODS: Sleep problems during the past night and the past 4 weeks were assessed by a self-administered questionnaire on overall sleep quality, disturbed sleep, sleep length and awakening problems. Saliva samples were collected in a single day, using cotton tubes, 30 min after awakening and again at 2000 h. A subsample of 387 participants collected saliva samples three-month later at awakening, +20 min and +40 min after awakening and at 2000 h. We adjusted for confounders related to sampling time, life style and personal characteristics, socioeconomic status and work aspects. RESULTS: Sleep problems during the past four weeks were associated with low morning and evening saliva cortisol concentrations: [-3.1% per score of disturbed sleep (p=.009); and -4.7% per score of awakening problems (p<.001)]. Whereas sleep problems were not related with slope (the morning to evening change in cortisol levels). Awakening problems predicted lower cortisol (-7.51% per score; p=.003) three-month later. Cortisol awakening response (CAR) and slope three-month later were significantly associated with disturbed sleep (-7.84% and -8.24%) and awakening problems (-6.93). Area under the curve (AUC(morning)) increased with disturbed sleep (3.77%). CONCLUSION: Surprisingly, low morning cortisol was associated with increased sleep problems during a four-week period prior to sampling among 4066 Danish civil servants. At follow-up three-month later, those with sleep problems had a flattened cortisol profile. Those with awakening problems also had low salivary cortisol in general.