Danish Nurse Cohort Research Articles

Long-term exposure to air pollution, road traffic noise, and heart failure incidence: the Danish Nurse Cohort

BACKGROUND AND AIM: Air pollution has been recognized as a risk factor for ischemic and coronary cardiovascular disease, while evidence on heart failure (HF) is more limited and novel. Moreover, no studies considered possible combined effects of co-exposure to air pollution and noise on HF, as high exposure to one pollutant may make the body more susceptible to the hazardous effects of another pollutant. We examined the association of long-term exposure to air pollution and road traffic noise with incident HF. METHODS: Using data on female nurses from the Danish Nurse Cohort ( 44 years), we investigated associations between 3-year mean exposures to air pollution and road traffic noise and incident HF using Cox regression models, adjusting for relevant confounders. Incidence of HF was defined as the first hospital contact (inpatient, outpatient, or emergency) between cohort baseline (1993 or 1999) and December 31, 2014, based on the Danish National Patient Register. Annual mean levels of particulate matter with a diameter 2.5 µm (PM2.5) since 1990, and nitrogen dioxide (NO2) and road traffic noise (Lden) since 1970 were estimated at participants' residences. RESULTS:Of the 22,189 nurses, 484 developed HF. We detected associations with all three pollutants, with hazard ratios (HR) and 95% confidence intervals (95% CI) of 1.35 (1.09-1.67), 1.09 (0.98-1.22), and 1.11 (0.99-1.26) per increase of 5.1 µg/m3 in PM2.5, 8.6 µg/m3 in NO2 and 9.3 dB in Lden, respectively. In mutually adjusted models, associations with PM2.5 remained most robust. Combination of exposure to high levels (75th vs. ≤75th percentile) of all three pollutants led to enhanced associations with HF incidence, with an HR of 1.46 (1.03-2.07). Former smokers and nurses with hypertension showed the strongest associations with PM2.5. CONCLUSIONS:We found that long-term exposures to air pollution and road traffic noise were independently and synergistically associated with HF. KEYWORDS: air pollution, cohort study, heart failure, morbidity, road traffic noise

Long-Term Exposure to Road Traffic Noise and Air Pollution, and Incident Atrial Fibrillation in the Danish Nurse Cohort

Background:Associations between long-term exposure to air pollution and road traffic noise have been established for ischemic heart disease, but findings have been mixed for atrial fibrillation (AF).Objectives:The goal of the study was to examine associations of long-term exposure to road traffic noise and air pollution with AF.Methods:Time-varying Cox regression models were used to estimate associations of 1-, 3-, and 23-y mean road traffic noise and air pollution exposures with AF incidence in 23,528 women enrolled in the Danish Nurse Cohort (age at baseline in 1993 or 1999). AF diagnoses were ascertained via the Danish National Patient Register. Annual mean weighted 24-h average road traffic noise levels () at the nurses’ residences, since 1970, were estimated using the Nord2000 model, and annual mean levels of particulate matter with a diameter () and nitrogen dioxide () were estimated using the DEHM/UBM/AirGIS model.Results:Of 23,528 nurses with no prior AF diagnosis at the cohort baseline, 1,522 developed AF during follow-up. In a fully adjusted model (including ), the estimated risk of AF was 18% higher [hazard ratio (HR); 95% confidence interval (CI): 1.18; 1.02, 1.36] in nurses with residential 3-y mean levels vs. , with similar findings for 1-y mean exposures. A increase in 3-y mean was associated with incident AF before and after adjustment for concurrent exposure to road traffic noise (HR 1.09; 95% CI: 1.00, 1.20 and 1.08; 95% CI: 0.97, 1.19, respectively). Associations with 1-y mean exposures were positive but closer to the null and not significant. Associations with were null for all time periods before and after adjustment for road traffic noise and inverse when adjusted for concurrent .Conclusion:Our analysis of prospective data from a cohort of Danish female nurses followed for up to 14 y provided suggestive evidence of independent associations between incident AF and 1- and 3-y exposures to road traffic noise and . https://doi.org/10.1289/EHP8090

Long-term exposure to road traffic noise and incident myocardial infarction: A Danish Nurse Cohort study.

Evidence of nonauditory health effects of road traffic noise exposure is growing. This prospective cohort study aimed to estimate the association between long-term exposure to road traffic noise above a threshold and incident myocardial infarction (MI) in Denmark. In the Danish Nurse Cohort study, we used data of 22,378 women, at recruitment in 1993 and 1999, who reported information on MI risk factors. The participants' first hospital contact or out-of-hospital death due to MI were followed-up until 2014. We investigated a relationship between residential exposures to road traffic noise levels (Lden) up to 23 years and incident MI (overall, nonfatal, and fatal) using time-varying Cox regression models adjusting for potential confounders and air pollutants. We estimated thresholds of road traffic noise (53, 56, and 58 dB) associated with incident MI in a piece-wise linear regression model. Of the 22,378 participants, 633 developed MI, 502 of which were nonfatal. We observed a non-linear relationship between the 23-year running mean of Lden and incident MI with a threshold level of 56 dB, above which hazard ratios (95% confidence intervals) were 1.30 (0.97, 1.75) for overall and 1.46 (1.05, 2.03) for nonfatal MI per 10 dB. The association with nonfatal MI attenuated slightly to 1.34 (0.95, 1.90) after adjustment for fine particles. We found that long-term exposure to road traffic noise above 56 dB may increase the risk of MI. The study findings suggest that road traffic noise above 56 dB may need regulation in addition to the regulation of ambient pollutants.

Shift work and incidence of psychiatric disorders: The Danish Nurse Cohort study

BackgroundResearch on health effects of shift work has especially focused on somatic diseases, such as breast cancer and cardiometabolic disease, while less attention has been given to the association between shift work and mental health. MethodsWe used information on 19 964 female nurses (≥44 years) from the Danish Nurse Cohort, who reported current work schedule (day, evening, night, or rotating) at recruitment (1993/1999). In 5102 nurses who participated in both cohort waves, we defined persistent night shift work as working night shift in 1993 and 1999. We used Cox regression models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for relevant confounders.Through linkage of cohort participants to national registers, we defined incidence of mood and neurotic disorders as first hospital contact or redeemed prescription until November 2018. ResultsWe found association between night shift work with mood disorders (HR = 1.31; 95%CI = 1.17–1.47) and neurotic disorders (1.29; 1.17–1.42), compared to day work. Associations were enhanced in nurses with persistent night shift work (1.85; 1.43–2.39 and 1.62; 1.26–2.09 for mood and neurotic disorders, respectively) and in nurses with specialist confirmed mood (1.69; 1.24–2.29) and neurotic (1.72; 1.22–2.44) disorders. Nurses with preexisting psychiatric disorders and full-time work seemed most susceptible. ConclusionsNight shift work is associated with increased risk of major psychiatric disorders. The novel suggestive findings of vulnerable groups, including nurses with a history of psychiatric disorders and full-time workers, are based on a limited number of cases, and further research is needed to confirm the results.

Long-term air pollution and road traffic noise exposure and COPD: the Danish Nurse Cohort.

While air pollution has been linked to the development of chronic obstructive pulmonary disease (COPD), evidence on the role of environmental noise is just emerging. We examined the associations of long-term exposure to air pollution and road traffic noise with COPD incidence. We defined COPD incidence for 24 538 female nurses from the Danish Nurse Cohort (age >44 years) as the first hospital contact between baseline (1993 or 1999) and 2015. We estimated residential annual mean concentrations of particulate matter with an aerodynamic diameter <2.5 µm (PM2.5) since 1990 and nitrogen dioxide (NO2) since 1970 using the Danish Eulerian Hemispheric Model/Urban Background Model/Air Geographic Information System modelling system, and road traffic noise (Lden) since 1970 using the Nord2000 model. Time-varying Cox regression models were applied to assess the associations of air pollution and road traffic noise with COPD incidence. 977 nurses developed COPD during a mean of 18.6 years' follow-up. We observed associations with COPD for all three exposures with HRs and 95% CIs of 1.19 (1.01-1.41) per 6.26 µg·m-3 for PM2.5, 1.13 (1.05-1.20) per 8.19 µg·m-3 for NO2 and 1.15 (1.06-1.25) per 10 dB for Lden. Associations with NO2 and Lden attenuated slightly after mutual adjustment, but were robust to adjustment for PM2.5. Associations with PM2.5 were attenuated to null after adjustment for either NO2 or Lden. No potential interaction effect was observed between air pollutants and noise. Long-term exposure to air pollution, especially traffic-related NO2, and to road traffic noise were independently associated with COPD.

Breast cancer rate after oophorectomy: A Prospective Danish Cohort Study.

The association between oophorectomy and risk of breast cancer in the general population is uncertain. The aim of our study was to determine the breast cancer rate in women from the general population after oophorectomy (performed before/after menopause), and whether this varies by use of hormone replacement therapy (HRT), hysterectomy, body mass index (BMI) and shift work. The study included 24 409 female nurses (aged ≥45 years) participating in the Danish Nurse Cohort. Nurses were followed from cohort entry until date of breast cancer, death, emigration or end of follow-up at 31 December 2018, whichever came first. Poisson regression with log-transformed person-years as the offset examined the association between oophorectomy and breast cancer (all ages and stratified by menopausal status at time of oophorectomy). The potential modifying effect of HRT use, hysterectomy, BMI and shift work on the associations was estimated. During 502 463 person-years of follow-up, 1975 (8.1%) nurses were diagnosed with breast cancer. Bilateral oophorectomy was associated with a reduced breast cancer rate compared to nurses with preserved ovaries, adjusted rate ratio (95% confidence interval): 0.79 (0.64; 0.99). Similar associations (magnitude and direction) were detected for unilateral oophorectomy and when stratifying according to menopausal status at time of oophorectomy, but without statistical significance. Unilateral and bilateral oophorectomy is associated with a reduced breast cancer rate in women from the general population. This association is not modified by use of HRT, hysterectomy, BMI or shift work.

Long-term exposure to ambient air pollution and road traffic noise and asthma incidence in adults: The Danish Nurse cohort

BackgroundAmbient air pollution is likely a risk factor for asthma, and recent evidence suggests the possible relevance of road traffic noise. ObjectivesWe examined the associations of long-term exposure to air pollution and road traffic noise with adult-asthma incidence. MethodsWe followed 28,731 female nurses (age > 44 years) from the Danish Nurse Cohort, recruited in 1993 and 1999, for first hospital contact for asthma from 1977 until 2015. We estimated residential annual mean concentrations of particulate matter with diameter < 2.5 µm (PM2.5) since 1990 and nitrogen dioxide (NO2) since 1970 with the Danish DEHM/UBM/AirGIS modeling system, and road traffic noise (Lden) since 1970 with the Nord2000 model. Time-varying Cox regression models were used to associate air pollution and road traffic noise exposure with asthma incidence. ResultsDuring 18.6 years’ mean follow-up, 528 out of 23,093 participants had hospital contact for asthma. The hazard ratios (HR) and 95% confidence intervals for asthma incidence associated with 3-year moving average exposures were 1.29 (1.03, 1.61) per 6.3 µg/m3 for PM2.5, 1.16 (1.07, 1.27) per 8.2 µg/m3 for NO2, and 1.12 (1.00, 1.25) per 10 dB for Lden. The HR for NO2 remained unchanged after adjustment for either PM2.5 or Lden, while the HRs for PM2.5 and Lden attenuated to unity after adjustment for NO2. ConclusionsLong-term exposure to air pollution was associated with adult-asthma incidence independently of road traffic noise, with NO2 most relevant. Road traffic noise was not independently associated with adult-asthma incidence.

Outdoor light at night and breast cancer incidence in the Danish Nurse Cohort

BackgroundKnowledge of the role of melatonin, xenograft experiments, and epidemiological studies suggests that exposure to light at night (LAN) may disturb circadian rhythms, possibly increasing the risk of developing breast cancer. ObjectivesWe examined the association between residential outdoor LAN and the incidence of breast cancer: overall and subtypes classified by estrogen (ER) and progesterone (PR) receptor status. MethodsWe used data on 16,941 nurses from the Danish Nurse Cohort who were followed-up from the cohort baseline in 1993 or 1999 through 2012 in the Danish Cancer Registry for breast cancer incidence and the Danish Breast Cancer Cooperative Group for breast cancer ER and PR status. LAN exposure data were obtained from the U.S. Defense Meteorological Satellite Program (DMSP) available for 1996, 1999, 2000, 2003, 2004, 2006, and 2010 in nW/cm2/sr unit, and assigned to the study participants’ residence addresses during the follow-up. Time-varying Cox regression models were used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between LAN and breast cancer, adjusting for individual characteristics, road traffic noise, and air pollution. ResultsOf 16,941 nurses, 745 developed breast cancer in total during 320,289 person-years of follow-up. We found no association between exposure to LAN and overall breast cancer. In the fully adjusted models, HRs for the highest (65.8–446.4 nW/cm2/sr) and medium (22.0–65.7 nW/cm2/sr) LAN tertiles were 0.97 (95% CI: 0.77, 1.23) and 1.09 (95% CI: 0.90, 1.31), respectively, compared to the lowest tertile of LAN exposure (0–21.9 nW/cm2/sr). We found a suggestive association between LAN and ER-breast cancer. ConclusionThis large cohort study of Danish female nurses suggests weak evidence of the association between LAN and breast cancer incidence.

Night work and incidence of Parkinson’s disease in the Danish Nurse Cohort

ObjectivesEvidence on the association between night work and Parkinson’s disease (PD) is sparse and conflicting, calling for more definitive studies.MethodsWe included 20 138 female nurses from the Danish Nurse Cohort...

Long-term exposure to road traffic noise and cause-specific mortality: a Danish Nurse Cohort Study

Background. There is growing evidence on the adverse effect of road traffic noise exposure on cardio- and cerebrovascular disease and diabetes morbidity, with limited data on mortality. We investigated whether long-term exposure to road traffic noise was associated with all-cause and cause-specific mortality. Methods. We linked 24,698 female nurses from the Danish Nurse Cohort, who at recruitment in 1993 or 1999 reported information on lifestyle, to the Danish Register of Causes of Death until the end of 2013. Road traffic noise levels in 1970-2013 were estimated by Nord2000 model as the annual mean of a weighted 24h average (Lden). We examined the associations between up to 23-year mean exposure to Lden and mortality using time-varying Cox regression models, adjusting for individual characteristics and particulate matter with diameter &lt; 2.5 µg/m3 (PM2.5). Results. During the mean follow-up of 17.5 years, 3,779 nurses died in total: 882 from cardiovascular disease (CVD), 277 from stroke, 76 from diabetes, 222 from dementia, 323 from respiratory disease (RD), and 1594 from cancer. Compared to a 5-year mean Lden &lt; 48 dB, fully adjusted hazard ratios (95% confidence intervals) for all-cause mortality were 1.13 (1.02-1.25) and 1.14 (1.02-1.28) for exposure levels between 48-58 dB and &gt; 58 dB, respectively. Corresponding estimates for CVD mortality were 1.23 (0.99-1.54) and 1.30 (1.02-1.67), for stroke mortality 2.01 (1.27-3.18) and 1.94 (1.17-3.22), for diabetes mortality 1.15 (0.54-2.48) and 1.53 (0.65-3.57), for dementia mortality 1.38 (0.84-2.26) and 1.36 (0.79-2.36), for RD mortality 1.20 (0.82-1.74) and 1.20 (0.79-1.84), and cancer mortality 1.01 (0.87-1.17) and 1.04 (0.88-1.24), respectively. HRs with 23-year mean of Lden were enhanced for all-cause and diabetes mortality, but attenuated for CVD, stroke, RD and dementia mortality. Conclusion: Long-term exposure to road traffic noise may increase risk of premature mortality independent of air pollution.

Outdoor Light at Night and Diabetes Incidence in the Danish Nurse Cohort Study

Background/Aim: Recent animal studies suggested that light-at-night (LAN) may impair glucose tolerance in rats and disturb glucose homeostasis. We aimed to evaluate the association between exposure to residential outdoor LAN and diabetes incidence in Denmark. Methods: In the nationwide Danish Nurse Cohort consisting of 23,797 nurses, recruited in 1993 or 1999, we identified 1,065 diabetes incident cases through National Diabetes Register up to 2012. The LAN data was estimated using Global Radiance Calibrated products of the Defense Meteorological Satellite Program (DMSP) for 1996, 1999, 2000, 2002, 2004, 2005, and 2010. The full residential address histories were obtained and the LAN exposure was assigned based on the 1996 data for addresses before 1997, and based on the most recent measure for addresses after 1997. Time-varying Cox regression models were used to estimate hazard ratios (HR) (95% confidence intervals (CI)) for the associations of LAN and diabetes incidence, adjusting for individual anthropometric, lifestyle and environmental covariates, such as residential air pollution (PM2.5 and NO2), and night-time road traffic noise determined by validated models. Results: The estimated HR based on a fully adjusted model for incident diabetes with an interquartile range (IQR) (75.6 nW/cm2/sr) increase in cumulative average outdoor LAN was 1.13 (95% CI: 1.05, 1.21). Based on the fully adjusted model of LAN exposure divided into quintiles, where LAN quintile 1 was reference, we found an increase in diabetes incidence at higher LAN levels: LAN quintile 2: HR: 1.04 (95% CI: 0.86-1.27, p = 0.66), LAN quintile 3: HR: 1.04 (95% CI: 0.85-1.26, p = 0.71), LAN quintile 4: HR: 0.99 (0.81-1.20, p = 0.91), and LAN quintile 5: HR: 1.21 (95% CI: 1.0-1.46, p = 0.053). Conclusion: We found suggestive evidence that outdoor LAN exposure may be associated with diabetes incidence, independent of air pollution and road traffic noise.

Long-term exposure to road traffic noise and incident heart failure ina Danish Nurse Cohort

Objectives: Evidence of the non-auditory effects of road traffic noise exposure on health is growing. We examined the association between long-term exposure to road traffic noise and incident heart failure (HF) using various exposure windows and thresholds of the road traffic noise. Methods: We used the Danish Nurse Cohort with 22,304 female nurses who at recruitment in 1993 and 1999 reported information on HF risk factors, and linked them to the Danish National Patient and Cause of Death Registries for the first hospital contact or out-of hospital death due to HF until 2014. Road traffic noise levels in 1970-2013 were estimated by Nord2000 model as the annual mean of a weighted 24h average (Lden). We examined the associations between multi-year (up to 23 years) exposures to Lden and HF incidence using time-varying Cox regression models and estimated the effects at or above the thresholds using piece-wise linear regression models after controlling for individual covariates and air pollution levels. Results: We observed a non-linear relationship between incident HF incidence (n=438) and road traffic noise. Notably, in models adjusting for individual covariates, the hazard ratio (HR) (95% confidence intervals [CI]) of incident HF was 1.22 (95% CI: 1.05, 1.42) per 10 dB of 23-year exposures at or above 37 dB. After controlling for PM2.5, the association was attenuated (HR:1.13 [95% CI: 0.96, 1.33]), but it remained robust to adjustment for NO2 (HR:1.21 [95% CI: 1.01, 1.46]). Associations were weaker with shorter exposure windows (1- and 3-year running mean of Lden). Conclusion: Long-term exposure to road traffic noise may increase the risk of HF.

Long-term Exposure to Low Concentration of PM2.5 and Mortality: A Danish Nurse Cohort Study

Background/Aim. The association between air pollution and mortality is well established, yet studies in areas with low levels of air pollution, below EU limit values, with adjustment for road traffic noise, are sparse. We examined the association of long-term exposure to fine particulate matter (PM2.5) with mortality due to cardiovascular disease (CVD), respiratory disease (RD), and diabetes as well as all-cause natural mortality.Methods. We used data on 24,541 female nurses from the Danish Nurse Cohort who, at recruitment in 1993 or 1999, reported information on risk factors. Data on death were obtained from the Danish Register of Causes of Death until the end of 2013. Annual mean concentrations of PM2.5 in 1990-2013 at the nurses’ residences were estimated using the Danish air pollution dispersion modeling system. We examined associations between the 3-year running mean of PM2.5 with all-cause natural and cause-specific mortality by using time-varying Cox Regression models, adjusting for individual characteristics.Results. During the study time-period, 3,708 nurses died, and of these, 843 were due to CVD, 310 due to RD, and 64 due to diabetes. The mean level of PM2.5 at the baseline was 20.5 µg/m3. In the fully adjusted models, including road traffic noise, we found positive associations of 3-year running mean of PM2.5 with all-cause natural (hazard ratio; 95% confidence interval: 1.06; 1.01-1.11), CVD (1.14; 1.03-1.26), and diabetes mortality (1.41; 1.05-1.90), per interquartile range of 4.39 μg/m3. In subjects exposed to low levels of PM2.5 (&lt; 20 µg/m3), we found even stronger association with all-cause natural (1.19; 1.11-1.27), CVD (1.27; 1.01-1.46), RD (1.27; 1.00-1.60), and diabetes mortality (1.44; 0.83-2.48).Conclusion. In a Danish cohort of female nurses, long-term exposures to low-levels of PM2.5 were associated with all-cause mortality, strongest for diabetes, and CVD, which persisted at the levels below the current EU limit values.

Outdoor Light at Night and Breast Cancer Incidence in the Danish Nurse Cohort Study

Introduction: Breast cancer is the most common cancer type, and the most common reason for cancer-related deaths among women worldwide. Animal and epidemiologic studies suggest that exposure to light at night may contribute to increased breast cancer risk through circadian disruption, which involves a decrease in the nocturnal secretion of melatonin followed by disturbed estrogen regulation, however, epidemiological evidence is limited. In this study, we examined the association between exposure to residential outdoor light at night (LAN) and breast cancer incidence in the Danish Nurse Cohort Study. Methods: We followed 20,404 Danish nurses from 1993 or 1999 through 2012. LAN exposure was estimated using the US Defense Meteorological Satellite Program's (DMSP) Operational Linescan System. We collected LAN data (nW/cm2/sr) for 1996, 1999, 2000, 2002, 2004, 2005, and 2010, assigned at the subject's residence during the follow-up. Data on the incidence of breast cancer was obtained from the Danish Cancer Registry. We used time-varying Cox regression models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for reproductive, lifestyle and environmental factors such as residential air pollution, road traffic noise, and greenspace. Results: Of the 20,490 women, 1,081 developed breast cancer in total during 339,633 person-years of follow-up. Based on the fully adjusted model of LAN exposure divided into quintiles, where the lowest LAN quintile was reference (0-13.6 nW/cm2/sr), we found an increase in breast cancer incidence at higher LAN levels: HR: 1.01 (95% CI: 0.83-1.23, p = 0.92), 1.08 (95% CI: 0.88-1.33, p = 0.44), 1.04 (0.83-1.30, p = 0.74), and 0.87 (95% CI: 0.66-1.15, p = 0.32) for the 2nd, 3rd, 4th, and 5th quintiles, respectively. Conclusion: There was a tendency, that higher levels of exposure to LAN were associated with a higher risk of breast cancer although the statistical significance was not observed.

Long-Term Exposure to Air Pollution and Road Traffic Noise and Incidence of Chronic Obstructive Pulmonary Disease: The Danish Nurse Cohort

Background: While air pollution has been linked to the development of chronic obstructive pulmonary disease (COPD), evidence on the role of environmental noise is just emerging. We examined the association of long-term exposure to air pollution and road traffic noise with COPD incidence. Methods: We defined COPD incidence for 24,538 female nurses from the Danish Nurse Cohort (age > 44 years) as the first hospital contact between baseline (1993 or 1999) and 2015. We estimated residential annual mean concentrations of particulate matter with diameter < 2·5 µm (PM2·5) since 1990 and nitrogen dioxide (NO2) since 1970 by the Danish DEHM/UBM/AirGIS modeling system, and road traffic noise (Lden) since 1970 by the Nord2000 model. Time-varying Cox regression models were applied to assess the associations of air pollution and noise with COPD incidence. Findings: 977 nurses developed COPD during 18·6 years’ mean follow-up. We observed associations with COPD for all three exposures with hazard ratios (HRs) and 95% confidence intervals (CIs) of 1·19 (1·01, 1·41) per 6·26 µg/m3 for PM2·5, 1·13 (1·05, 1·20) per 8·19 µg/m3 for NO2, and 1·15 (1·06, 1·25) per 10 dB for Lden. Associations with NO2 and Lden attenuated slightly after adjustment for each other, but were robust to adjustment for PM2·5. Associations with PM2·5 were attenuated to null after adjustment for either NO2 or Lden. Interpretation: Long-term exposures to traffic-related NO2 and road traffic noise were associated with COPD, independent of each other. Funding Statement: Danish Council for Independent Research, Novo Nordisk Foundation, and China Scholarship Council. Funding Statement: This work was supported by the Danish Council for Independent Research [DFF-4183-00353], the Novo Nordisk Foundation Challenge Programme [NNF17OC0027812], and the China Scholarship Council [No. 201806010406]. Declaration of Interests: We declare that we have no conflicts of interest. Ethics Approval Statement: The establishment of the cohort was approved by the Scientific and Ethical Committee of Copenhagen and Frederiksberg Municipalities, and the Danish Data Protection Agency.

Long-term exposure to low levels of air pollution and mortality adjusting for road traffic noise: A Danish Nurse Cohort study

BackgroundThe association between air pollution and mortality is well established, yet some uncertainties remain: there are few studies that account for road traffic noise exposure or that consider in detail the shape of the exposure–response function for cause-specific mortality outcomes, especially at low-levels of exposure. ObjectivesWe examined the association between long-term exposure to particulate matter [(PM) with a diameter of <2.5 µm (PM2.5), <10 µm (PM10)], and nitrogen dioxide (NO2) and total and cause-specific mortality, accounting for road traffic noise. MethodsWe used data on 24,541 females (age > 44 years) from the Danish Nurse Cohort, who were recruited in 1993 or 1999, and linked to the Danish Causes of Death Register for follow-up on date of death and its cause, until the end of 2013. Annual mean concentrations of PM2.5, PM10, and NO2 at the participants’ residences since 1990 were estimated using the Danish DEHM/UBM/AirGIS dispersion model, and annual mean road traffic noise levels (Lden) were estimated using the Nord2000 model. We examined associations between the three-year running mean of PM2.5, PM10, and NO2 with total and cause-specific mortality by using time-varying Cox Regression models, adjusting for individual characteristics and residential road traffic noise. ResultsDuring the study period, 3,708 nurses died: 843 from cardiovascular disease (CVD), 310 from respiratory disease (RD), and 64 from diabetes. In the fully adjusted models, including road traffic noise, we detected associations of three-year running mean of PM2.5 with total (hazard ratio; 95% confidence interval: 1.06; 1.01–1.11), CVD (1.14; 1.03–1.26), and diabetes mortality (1.41; 1.05–1.90), per interquartile range of 4.39 μg/m3. In a subset of the cohort exposed to PM2.5 < 20 µg/m3, we found even stronger association with total (1.19; 1.11–1.27), CVD (1.27; 1.01–1.46), RD (1.27; 1.00–1.60), and diabetes mortality (1.44; 0.83–2.48). We found similar associations with PM10 and none with NO2. All associations were robust to adjustment for road traffic noise. DiscussionLong-term exposure to low-levels of PM2.5 and PM10 is associated with total mortality, and mortality from CVD, RD, and diabetes. Associations were even stronger at the PM2.5 levels below EU limit values and were independent of road traffic noise.

Shift work and incidence of dementia: A Danish Nurse Cohort study.

A few studies suggest that working night and rotating shifts increase the risk of dementia. We examined the association between shift work and the incidence of dementia in a cohort of female Danish nurses. We linked Danish Nurse Cohort participants, who reported work schedules (day, evening, night, rotating shifts) in 1993 and/or 1999 and their duration in 2009, to Danish registers to obtain information on dementia hospitalizations and prescription medication until November 2018. Among 6048 nurses who reported work schedules in 1993 and 1999, nurses working night shifts ≥6 years had higher dementia incidence (hazard ratio: 2.43, 95% confidence interval: 1.39 to 4.23) than those working day shifts ≥6 years. Among 8059 nurses who reported shift work duration, nurses working night shifts ≥6 years had higher dementia incidence than those working night shifts <1 year (1.47, 1.06 to 2.06). Persistent night shift work may increase the risk of dementia.

Smoking cessation prolongs survival in female cancer survivors - the Danish nurse cohort.

To explore smoking cessation between cancer survivors and cancer-free women, and the potential survival benefits from smoking cessation in cancer surviving women. We pooled 46,334 responses from the Danish Nurse Cohort. The cohort consists of female nurses, who were invited for surveys in 1993, 1999 and 2009. Participants were linked to nationwide registries on hospitalization, cause of death and migration through 2016. Odds for smoking cessation by cancer diagnosis were computed in propensity score matched logistic regression models, while survival by postdiagnosis smoking cessation was estimated in cox proportional hazards models. Eligible for analysis were 7841 women (mean age=56.7 years, SD±7.2), who were smokers at baseline and survived to the next follow-up survey. Of these, 545 women were diagnosed with cancer and matched by propensity score (1:2) with 1090 cancer-free women. Odds for smoking cessation were significantly higher in cancer-diagnosed women compared to their cancer-free peers (OR=1.31, 95% CI: 1.06-1.61). Moreover, mortality risk was significantly lower among cancer survivors who stopped smoking (HR=0.64, 95% CI: 0.46-0.91), compared to persistent smokers. The results suggest considerable survival benefits from smoking cessation in cancer surviving female nurses, and that the time surrounding cancer diagnosis may serve as a teachable moment for smoking cessation. However, due to substantial methodological limitations embedded in the study, careful interpretation of the presented results is warranted. Future studies are needed to demonstrate the effects of diagnosis on smoking cessation as well as the effects of smoking cessation on survival in female cancer populations.

Long-term exposure to air pollution and stroke incidence: A Danish Nurse cohort study

Ambient air pollution has been linked to stroke, but few studies have examined in detail stroke subtypes and confounding by road traffic noise, which was recently associated with stroke. Here we examined the association between long-term exposure to air pollution and incidence of stroke (overall, ischemic, hemorrhagic), adjusting for road traffic noise. In a nationwide Danish Nurse Cohort consisting of 23,423 nurses, recruited in 1993 or 1999, we identified 1,078 incident cases of stroke (944 ischemic and 134 hemorrhagic) up to December 31, 2014, defined as first-ever hospital contact. The full residential address histories since 1970 were obtained for each participant and the annual means of air pollutants (particulate matter with diameter < 2.5 µm and < 10 µm (PM2.5 and PM10), nitrogen dioxide (NO2), nitrogen oxides (NOx)) and road traffic noise were determined using validated models. Time-varying Cox regression models were used to estimate hazard ratios (HR) (95% confidence intervals (CI)) for the associations of one-, three, and 23-year running mean of air pollutants with stroke adjusting for potential confounders and noise. In fully adjusted models, the HRs (95% CI) per interquartile range increase in one-year running mean of PM2.5 and overall, ischemic, and hemorrhagic stroke were 1.12 (1.01–1.25), 1.13 (1.01–1.26), and 1.07 (0.80–1.44), respectively, and remained unchanged after adjustment for noise. Long-term exposure to ambient PM2.5 was associated with the risk of stroke independent of road traffic noise.

Long-Term Exposure to Air Pollution and Incidence of Myocardial Infarction: A Danish Nurse Cohort Study.

Background:Air pollution exposure has been linked to coronary heart disease, although evidence on and myocardial infarction (MI) incidence is mixed.Objectives:This prospective cohort study aimed to investigate associations between long-term exposure to air pollution and MI incidence, adjusting for road traffic noise.Methods:We used data from the nationwide Danish Nurse Cohort on 22,882 female nurses ( of age) who, at recruitment in 1993 or 1999, reported information on cardiovascular disease risk factors. Data on MI incidence was collected from the Danish National Patient Register until the end of 2014. Annual mean concentrations of particulate matter (PM) with a diameter (), , nitrogen dioxide (), and nitrogen oxides () at the nurses’ residences since 1990 ( and ) or 1970 ( and ) were estimated using the Danish Eulerian Hemispheric Model/Urban Background Model/AirGIS (DEHM/UBM/AirGIS) dispersion model. We used time-varying Cox regression models to examine the association between 1- and 3-y running means of these pollutants, as well as 23-y running means of and , with both overall and fatal incident MI. Associations were explored in three progressively adjusted models: Model 1, adjusted for age and baseline year; Model 2, with further adjustment for potential confounding by lifestyle and cardiovascular disease risk factors; and Model 3, with further adjustment for road traffic noise, modeled as the annual mean of a weighted 24-h average ().Results:Of the 22,882 women, 641 developed MI during a mean follow-up of 18.6 y, 121 (18.9%) of which were fatal. Reported hazard ratios (HRs) were based on interquartile range increases of 5.3, 5.5, 8.1, and for , , , and , respectively. In Model 1, we observed a positive association between a 3-y running mean of and an overall incident MI with an (95% CI: 1.07, 1.35), which attenuated to (95% CI: 0.92, 1.23) in Model 2. In Model 1 for incident fatal MI, we observed a strong association with a 3-y running mean of , with an (95% CI: 1.33, 2.13), which attenuated to (95% CI: 1.01, 1.81) in Model 2. Similar associations were seen for , with 3-y, Model 2 estimates for overall and fatal incident MI of (95% CI: 0.91, 1.23) and (95% CI: 1.01, 1.81), respectively. No evidence of an association was observed for or . For all pollutants, associations in Model 2 were robust to further adjustment for road traffic noise in Model 3 and were similar for a 1-y running mean exposure.Conclusions:We found no association between long-term exposure to , , , or and overall MI incidence, but we observed positive associations for and with fatal MI. We present novel findings that the association between PM and MI incidence is robust to adjustment for road traffic noise. https://doi.org/10.1289/EHP5818