Danish Nurse Cohort Research Articles

Long-term exposure to air pollution and lung cancer incidence in the Danish Nurse Cohort

Long-term exposure to air pollution and lung cancer incidence in the Danish Nurse Cohort

Long-term exposure to air pollution and lung cancer survival in the Danish Nurse Cohort

Long-term exposure to air pollution and lung cancer survival in the Danish Nurse Cohort

Long-term exposure to road traffic noise and acute lower respiratory infections in the Danish Nurse Cohort

BackgroundLong-term exposure to road traffic noise is associated with cardiovascular disease, but the evidence on respiratory diseases is just emerging. We aimed to examine the association between long-term exposure to road traffic noise and the incidence of acute lower respiratory infections (ALRIs) in adults. MethodsWe followed 23,141 female nurses (age ≥ 44 years) from the Danish Nurse Cohort from baseline (1993 or 1999) to their first hospital contact (inpatient, outpatient, or emergency room) for ALRI, death, emigration or the end of 2015. The residential annual mean levels of road traffic noise (Lden) during the follow-up were estimated using the Nord2000 model. We applied time-varying Cox models to estimate the association of 3-year mean exposure to Lden with ALRIs incidence and piecewise analysis to estimate the threshold of Lden. We examined the robustness of the results by adjusting for residential exposure to air pollution, and the effect modification by attained age, socioeconomic status (SES), comorbidity, and lifestyle. ResultsDuring 18.5 years of follow-up, 2,004 nurses developed ALRIs. In a linear model, we detected a statistically significant positive association between Lden and ALRI, with a hazard ratio (HR) of 1.11 (95 % confidence interval (CI): 1.04, 1.17) per 9.2 dB (interquartile range, IQR). We observed non-linear association with a threshold at 57 dB, above which the HR was 1.25 (95 % CI: 1.09, 1.43) per IQR. Further adjustment for PM2.5 reduced the HRs slightly to 1.21 (95 % CI: 1.04, 1.40). The associations were stronger for nurses with asthma, and in those with lowest SES. ConclusionWe present novel findings in support of the association between long-term exposure to road traffic noise and ALRIs, independent of air pollution, suggesting noise as a risk factor for infectious respiratory diseases.

Long-term exposure to air pollution and road traffic noise and incidence of dementia in the Danish Nurse Cohort.

We examined the association of long-term exposure to air pollution and road traffic noise with dementia incidence in the Danish Nurse Cohort. Female nurses were followed for dementia incidence (hospital contact or medication prescription) from 1993/1999 to 2020. Air pollution and road traffic noise levels were estimated at nurses' residences, and their associations with dementia were examined using Cox regression models. Of 25,233 nurses 1409 developed dementia. Particulate matter with a diameter of ≤2.5µm (PM2.5) was associated with dementia incidence, after adjusting for lifestyle, socioeconomic status, and road traffic noise (hazard ratio [95% confidence interval] 1.35 [1.15-1.59] per interquartile range of 2.6µg/m3). There was no association of PM2.5 with dementia in physically active nurses. Association with road traffic noise diminished after adjusting for PM₂.₅ (1.02 [0.93-1.11] per 7.6dB). Long-term exposure to air pollution increases risk of dementia, and physical activity may moderate this risk. Long-term exposure to air pollution was associated with increased risk of dementia among female nurses from the Danish Nurse Cohort. Association of air pollution with dementia was independent of road traffic noise. Association of road traffic noise with dementia diminished after adjusting for air pollution. Physical activity moderated adverse effects of air pollution on dementia.

Long-Term Exposure to Air Pollution and Risk of Acute Lower Respiratory Infections in the Danish Nurse Cohort.

Rationale: Air pollution is a major risk factor for chronic cardiorespiratory diseases, affecting the immune and respiratory systems' functionality, but epidemiological evidence in respiratory infections remains sparse. Objectives: We aimed to assess the association of long-term exposure to ambient air pollution with the risk of developing new and recurrent acute lower respiratory infections (ALRIs), characterized by persistently severe symptoms necessitating hospital contact, and identify the potential susceptible populations by socioeconomic status, smoking, physical activity status, overweight, and comorbidity with chronic lung disease. Methods: We followed 23,912 female nurses from the Danish Nurse Cohort (age >44 yr) from baseline (1993 or 1999) until 2018 for incident and recurrent ALRIs defined by hospital contact (inpatient, outpatient, and emergency room) data from the National Patient Register. Residential annual mean concentrations of fine particulate matter, nitrogen dioxide (NO2), and black carbon were modeled using the Danish Eulerian Hemispheric Model/Urban Background Model/Air Geographic Information System. We used marginal Cox models with time-varying exposures to assess the association of 3-year running mean air pollution level with incident and recurrent ALRIs and examined effect modification by age, socioeconomic status, smoking, physical activity, body mass index, and comorbidity with asthma or chronic obstructive pulmonary disease (COPD). Results: During a 21.3-year mean follow-up, 4,746 ALRIs were observed, of which 2,553 were incident. We observed strong positive associations of all three pollutants with incident ALRIs, with hazard ratios and 95% confidence intervals of 1.19 (1.08-1.31) per 2.5 μg/m3 for fine particulate matter, 1.17 (1.11-1.24) per 8.0 μg/m3 for NO2, and 1.09 (1.05-1.12) per 0.3 μg/m3 for black carbon, and slightly stronger associations with recurrent ALRIs. Associations were strongest in patients with COPD and nurses with low physical activity. Conclusions: Long-term exposure to air pollution at low levels was associated with risks of new and recurrent ALRIs, with patients with COPD and physically inactive subjects most vulnerable.

Long-term exposure to air pollution and risk of acute lower respiratory infections: The Danish Nurse Cohort

Long-term exposure to air pollution and risk of acute lower respiratory infections: The Danish Nurse Cohort

Associations between air pollution, road traffic noise and incidence of dementia in the Danish Nurse Cohort

Associations between air pollution, road traffic noise and incidence of dementia in the Danish Nurse Cohort

Associations between residential distance to green or blue space and hospitalization for cardiovascular disease: a Danish Nurse Cohort study

Associations between residential distance to green or blue space and hospitalization for cardiovascular disease: a Danish Nurse Cohort study

Depression in Mid- and Later-Life and Risk of Dementia in Women: A Prospective Study within the Danish Nurses Cohort.

Depression and dementia confer substantial global health burdens, particularly in women. Understanding the association between depression and dementia may inform new targets for prevention and/or early intervention. To investigate the association between depression in mid- and later-life and dementia (all-cause, Alzheimer's disease (AD) or vascular dementia (VaD)) in women. A prospective study design. Nurses were followed from age 60 years or entry into the cohort, whichever came last, until date of dementia, death, emigration, or end of follow-up, whichever came first. Cox regression models with age as the underlying timeline were used to estimate the associations between time-varying depression and incident dementia. The study included 25,651 female Danish nurses (≥45 years) participating in the Danish Nurse Cohort. During an average of 23 years of follow-up, 1,232 (4.8%) nurses developed dementia and 8,086 (31.5%) were identified with at least two episodes of treated depression. In adjusted analyses, nurses with depression were at a statistically significant 5.23-fold higher risk of all-cause dementia (aHR 5.23:95% CI, 4.64-5.91) compared to those with no history of depression. The differential effects of depression were greater for VaD (aHR 7.96:95% CI, 5.26-12.0) than AD (aHR 4.64:95% CI, 3.97-5.42). Later life depression (>60 years) (aHR 5.85:95% CI, 5.17-6.64) and recurrent depression (aHR 3.51:95% CI, 2.67-4.61) elevated dementia risk. Severe depression tripled the risk of all cause dementia (aHR 3.14:95% CI, 2.62-3.76). Both later life and severe depression substantially increase dementia risk in women, particularly VaD.

Risk of Fracture After Bilateral Oophorectomy.

Fragility fractures, resulting from low-energy trauma, occur in approximately 1 in 10 Danish women aged 50 years or older. Bilateral oophorectomy (surgical removal of both ovaries) may increase the risk of fragility fractures due to loss of ovarian sex steroids, particularly estrogen. We investigated the association between bilateral oophorectomy and risk of fragility fracture and whether this was conditional on age at time of bilateral oophorectomy, hormone therapy (HT) use, hysterectomy, physical activity level, body mass index (BMI), or smoking. We performed a cohort study of 25,853 female nurses (≥45 years) participating in the Danish Nurse Cohort. Nurses were followed from age 50 years or entry into the cohort, whichever came last, until date of first fragility fracture, death, emigration, or end of follow-up on December 31, 2018, whichever came first. Cox regression models with age as the underlying time scale were used to estimate the association between time-varying bilateral oophorectomy (all ages, <51/≥51 years) and incident fragility fracture (any and site-specific [forearm, hip, spine, and other]). Exposure and outcome were ascertained from nationwide patient registries. During 491,626 person-years of follow-up, 6600 nurses (25.5%) with incident fragility fractures were identified, and 1938 (7.5%) nurses had a bilateral oophorectomy. The frequency of fragility fractures was 24.1% in nurses who were <51 years at time of bilateral oophorectomy and 18.1% in nurses who were ≥51 years. No statistically significant associations were observed between bilateral oophorectomy at any age and fragility fractures at any site. Neither HT use, hysterectomy, physical activity level, BMI, nor smoking altered the results. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Role of shift work in dietary changes among Danish nurses.

Research indicates that shift work is associated with dietary changes and the development of chronic diseases. To assess if moving from day work into shift work is associated with dietary changes in Danish nurses. Binary variables of changes in food consumption were created using data from the 1993 and 1999 surveys of the Danish Nurse Cohort. Analyses were carried out using multiple logistic regression in SPSS to assess how dietary practices changed in nurses who moved from day work into shift work compared with those who remained in day work. This study included 763 nurses who changed from Day to Shift work and 4022 nurses who continued to work days. Nurses who moved from day work into shift work were more likely to decrease their potato and vegetable intake odds ratio (OR) 1.31 (1.04-1.63). There was no difference in the frequency of coffee, milk or cheese consumption. New shift workers consumed more fatty meat OR 1.82 (1.23-2.69), sausages OR 1.37 (1.09-1.73) and cream/whipped cream/butter OR 1.61 (1.25-2.07) when they had avoided these foods in the past, compared to those who remained in day work. The majority of Danish nurses made little change to their diet as a result of moving into shift work, but some made dietary changes that were generally unhealthy compared with those who remained in day work. Employers of nurses should consider implementing health promotional activities, facilitating access and/or providing healthy eating options in nurses moving from Day to Shift work.

How do reproductive history and anthropometry in midlife relate to later risk of pelvic organ prolapse? A prospective cohort study.

The objective was to examine the association between reproductive and anthropometric factors and later risk of pelvic organ prolapse (POP). We carried out a prospective cohort study including 11,114 female nurses > 44years from the Danish Nurse Cohort. In 1993, the study population was recruited through the Danish Nurse Organization and self-reported data on age, height, weight, age at menarche, age at first birth and number of childbirths were obtained. POP diagnosis was obtained from the National Patient Registry. Risk of POP was estimated using COX regression and presented as hazard ratios (HR) with 95% confidence intervals (CI). Overall, 10% of the women received a diagnosis of POP within a median follow-up of 22years. A 4% increase in risk of POP was seen for each increasing BMI (kg/m2) unit at baseline. Compared to women of normal weight, higher risks of POP were seen in overweight (HR 1.18: 1.02-1.36) and obese women (HR 1.33: 1.02-1.74), while underweight had a lower risk (HR 0.51: 0.27-0.95). Compared to women with one childbirth, women with no childbirths had a reduced risk of 57% while increased risks of 46%, 78% and 137% were observed in women with two, three and four childbirths. Women with menarche before the age of 12 tended to have a higher risk of POP as did women who were 30-33years at their first childbirth. POP is a common health problem in women, and BMI and number of childbirths are strong predictors.

Oophorectomy and rate of dementia: a prospective cohort study.

Globally, dementia disproportionally affects women, which is not fully explained by higher female longevity. Oophorectomy at any age leads to the permanent loss of ovarian sex steroids, potentially increasing the risk of dementia. We aimed to investigate the association between oophorectomy and dementia and whether this was conditional on age at oophorectomy, hysterectomy or use of hormone therapy (HT). A prospective study of 24,851 female nurses from the Danish Nurse Cohort. Nurses were followed from age 60 years or entry into the cohort, whichever came last, until date of dementia, death, emigration or end of follow-up (December 31, 2018), whichever came first. Poisson regression models with log-transformed person-years as offset were used to estimate the associations. During 334,420 person-years of follow-up, 1,238 (5.0%) nurses developed dementia and 1,969 (7.9%)/ 1,016 (4.1%) contributed person-time after bilateral-/unilateral oophorectomy. In adjusted analyses, an 18% higher rate of dementia was observed following bilateral oophorectomy (aRR 1.18: 95% CI, 0.89-1.56) and 13% lower rate (aRR 0.87: 95% CI, 0.59-1.23) following unilateral oophorectomy compared to nurses who retained their ovaries. Similar effects were detected after stratification according to age at oophorectomy. No statistically significant modifying effects of hysterectomy or HT were detected (Pinteraction≥0.60). Bilateral, but not unilateral, oophorectomy was associated with an increased rate of incident dementia. We were unable to establish whether this association was conditional on hysterectomy or HT use. Although an increase in dementia after bilateral oophorectomy is biologically plausible, limited statistical power hampers the precision of the estimates.

The long-term association between bilateral oophorectomy and depression: a prospective cohort study.

Depression is a leading cause of disability globally and affects more women than men. Ovarian sex steroids are thought to modify depression risk in women and interventions such as bilateral oophorectomy that permanently change the sex steroid milieu may increase the risk of depression. This study aimed to investigate the associations between unilateral and bilateral oophorectomy and depression over a 25-year period (1993-2018) and whether this varied by age at oophorectomy or use of menopausal hormone therapy. Twenty-five thousand one hundred eighty-eight nurses aged ≥45 years from the Danish Nurse Cohort were included. Nurses with depression prior to baseline were excluded. Poisson regression models, with log-transformed person-years as offset, were used to assess the associations between oophorectomy and incident depression. Nurses who retained their ovaries were the reference group. Compared with nurses with retained ovaries, bilateral oophorectomy was associated with a slightly higher rate of depression (rate ratio [RR], 1.08; 95% confidence interval [CI], 0.95-1.23), but without statistical significance. However, when stratified by age at oophorectomy, compared with nurses with retained ovaries, bilateral oophorectomy at age ≥51 years was associated with higher rates of depression (RR 1.16; 95% CI, 1.00-1.34), but not bilateral oophorectomy at age <51 years (RR 0.86; 95% CI, 0.69-1.07); P value for difference in estimates = 0.02. No association between unilateral oophorectomy and depression was observed. In this cohort of Danish female nurses, bilateral oophorectomy at age ≥51 years, but not at younger ages, was associated with a slightly higher rate of depression compared with those who retained their ovaries.

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

BackgroundLong-term road traffic noise exposure is linked to cardio-metabolic disease morbidity, whereas evidence on mortality remains limited. ObjectivesWe investigated association of long-term exposure to road traffic noise with all-cause and cause-specific mortality. MethodsWe linked 22,858 females from the Danish Nurse Cohort (DNC), recruited into the Danish Register of Causes of Death up to 2014. Road traffic noise levels since 1970 were modelled by Nord2000 as the annual mean of a weighted 24 h average (Lden). Cox regression models examined the associations between Lden (5-year and 23-year means) and all-cause and cause-specific mortalities, adjusting for lifestyle and exposure to PM2.5 (particulate matter with diameter < 2.5 μm) and NO2 (nitrogen dioxide). ResultsDuring follow-up (mean 17.4 years), 3902 nurses died: 1622 from cancer, 922 from CVDs (289 from stroke), 338 from respiratory diseases (186 from chronic obstructive pulmonary disease, 114 from lower respiratory tract infections [ALRIs]), 234 from dementia, 95 from psychiatric disorders, and 79 from diabetes. Hazard ratios (95% confidence intervals) for all-cause mortality from fully-adjusted models were 1.06 (1.01, 1.11) and 1.09 (1.03, 1.15) per 10 dB of 5-year and 23-year mean Lden, respectively, which attenuated slightly in our main model (fully-adjusted plus PM2.5: 1.04 [1.00, 1.10]; 1.08 [1.02, 1.13]). Main model estimates suggested the strongest associations between 5-year mean Lden and diabetes (1.14: 0.81, 1.61), ALRIs (1.13: 0.84, 1.54), dementia (1.12: 0.90, 1.38), and stroke (1.10: 0.91, 1.31), whereas associations with 23-year mean Lden were suggested for respiratory diseases (1.15: 0.95, 1.39), psychiatric disorders (1.11: 0.78, 1.59), and all cancers (1.08: 0.99, 1.17). DiscussionAmong the female nurses from the DNC, we observed that long-term exposure to road traffic noise led to premature mortality, independently of air pollution, and its adverse effects may extend well beyond those on the cardio-metabolic system to include respiratory diseases, cancer, neurodegenerative and psychiatric disorders.

Long-term exposure to road traffic noise and stroke incidence: a Danish Nurse Cohort study

BackgroundRoad traffic noise has been linked to increased risk of ischemic heart disease, yet evidence on stroke shows mixed results. We examine the association between long-term exposure to road traffic noise and incidence of stroke, overall and by subtype (ischemic or hemorrhagic), after adjustment for air pollution.MethodsTwenty-five thousand six hundred and sixty female nurses from the Danish Nurse Cohort recruited in 1993 or 1999 were followed for stroke-related first-ever hospital contact until December 31st, 2014. Full residential address histories since 1970 were obtained and annual means of road traffic noise (Lden [dB]) and air pollutants (particulate matter with diameter < 2.5 μm and < 10 μm [PM2.5 and PM10], nitrogen dioxide [NO2], nitrogen oxides [NOx]) 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 means of Lden preceding stroke (all, ischemic or hemorrhagic), adjusting for stroke risk factors and air pollutants. The World Health Organization and the Danish government’s maximum exposure recommendations of 53 and 58 dB, respectively, were explored as potential Lden thresholds.ResultsOf 25,660 nurses, 1237 developed their first stroke (1089 ischemic, 148 hemorrhagic) during 16 years mean follow-up. For associations between a 1-year mean of Lden and overall stroke incidence, the estimated HR (95% CI) in the fully adjusted model was 1.06 (0.98–1.14) per 10 dB, which attenuated to 1.01 (0.93–1.09) and 1.00 (0.91–1.09) in models further adjusted for PM2.5 or NO2, respectively. Associations for other exposure periods or separately for ischemic or hemorrhagic stroke were similar. There was no evidence of a threshold association between Lden and stroke.ConclusionsLong-term exposure to road traffic noise was suggestively positively associated with the risk of overall stroke, although not after adjusting for air pollution.

Cardiovascular mortality after bilateral oophorectomy: a prospective cohort study.

Bilateral oophorectomy permanently reduces endogenous estrogen exposure and may increase cardiovascular mortality in women. This study aimed to investigate the association between bilateral oophorectomy and cardiovascular mortality and whether this association was conditional on hysterectomy or on the use of hormone therapy at the time of study entry. A prospective cohort study of 25,338 female nurses aged ≥ 45 years within the Danish Nurse Cohort. Nurses were enrolled in 1993 or 1999 and followed until death, emigration, or end of follow-up on December 31, 2018, whichever came first. Exposure was bilateral oophorectomy. Outcome was cardiovascular mortality. Associations were estimated using Poisson regression models with log person-years as the offset. A total of 2,040 (8.1%) participants underwent bilateral oophorectomy. During a mean follow-up of 21.2 (SD: 5.6) years, 772 (3.0%) nurses died from cardiovascular disease. In adjusted analyses, a 31% higher rate of cardiovascular mortality was observed after bilateral oophorectomy (aMRR 1.31; 95% CI, 0.88-1.96) compared with women who retained their ovaries. No evidence of effect modification by use of hormone therapy at baseline or by hysterectomy on the association between bilateral oophorectomy and cardiovascular mortality was observed. Bilateral oophorectomy may be associated with cardiovascular mortality in women, but the estimate was not statistically significant. Additionally, we were unable to make firm conclusions regarding the possible modifying role of hormone therapy and hysterectomy on this potential association. Additional studies are needed to replicate this work.

The association between general and central obesity and the risks of coronary heart disease in women with and without a familial predisposition to obesity: findings from the Danish Nurse Cohort.

Several studies show an increased risk of coronary heart disease (CHD) among people with obesity, but it is largely unknown whether this association also depends on a familial predisposition to obesity. This study examined if associations between Body Mass Index (BMI) or waist circumference (WC) and incident CHD differed among Danish female nurses with and without familial overweight and obesity. Analyses were based on data from the Danish Nurse Cohort (n = 20,701). Self-reported height, weight and self-measured WC were assessed in 1999, as was information on familial overweight/obesity, defined as having one or both parents with overweight/obesity. Information on the development of or death from CHD was collected from nationwide Danish registries in 2015. Analyses were based on Cox proportional hazard regression models adjusted for potential confounding factors. Both BMI and WC were directly associated with CHD risk, but we found no evidence of effect modification from familial predisposition to obesity. Hence a familial predisposition to obesity does not seem to influence the risk of CHD associated with general or central obesity.

Long-Term Exposure to Air Pollution, Road Traffic Noise, and Heart Failure Incidence: The Danish Nurse Cohort.

BackgroundWe examined the association of long‐term exposure to air pollution and road traffic noise with incident heart failure (HF).Methods And ResultsUsing data on female nurses from the Danish Nurse Cohort (aged >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 since 1990 and NO2 and road traffic noise since 1970 were estimated at participants' residences. Of the 22 189 nurses, 484 developed HF. We detected associations with all 3 pollutants, with hazard ratios (HRs) of 1.17 (95% CI, 1.01–1.36), 1.10 (95% CI, 0.99–1.22), and 1.12 (95% CI, 0.99–1.26) per increase of 5.1 µg/m3 in particulate matter with a diameter <2.5 µm, 8.6 µg/m3 in NO2, and 9.3 dB in road traffic noise, respectively. We observed an enhanced risk of HF incidence for those exposed to high levels of the 3 pollutants; however, the effect modification of coexposure was not statistically significant. Former smokers and nurses with hypertension showed the strongest associations with particulate matter with a diameter <2.5 µm (P effect modification<0.05).ConclusionsWe found that long‐term exposures to air pollution and road traffic noise were independently associated with HF.

Bilateral oophorectomy and rate of colorectal cancer: A prospective cohort study.

Worldwide, colorectal cancer is the second most common cancer and third cause of cancer death in women. Estrogen exposure has been inversely associated with colorectal cancer. Oophorectomy reduces circulating estrogen, but the effect on colorectal cancer remains uncertain. The aim of this study was to examine the association between unilateral and bilateral oophorectomy and subsequent risk of colorectal cancer, and whether this association varied by menopausal status at time of oophorectomy, use of hormone replacement therapy (HRT) at baseline, hysterectomy and baseline body mass index (BMI). The study included 25 698 female nurses (aged ≥45 years) participating in the Danish Nurse Cohort. Nurses were followed from baseline until date of colorectal cancer, death, emigration or end of follow-up at December 31, 2018, whichever came first. We examined the association between oophorectomy and colorectal cancer (all ages and stratified by menopausal status). The potential modifying effects of hysterectomy, HRT use at baseline and BMI were investigated. During 542 140 person-years of follow-up, 863 (3.4%) nurses were diagnosed with colorectal cancer. Bilateral oophorectomy was associated with a 79% increased colorectal cancer rate, adjusted rate ratio (aRR) (95% confidence interval [CI]): 1.79 (1.33-2.42). Effect estimates following unilateral oophorectomy also showed higher rate of colorectal cancer, although less pronounced and nonstatistically significant (aRR) (95%CI): 1.25 (0.86-1.82). Similar results were seen when stratifying by menopausal status. The association was not modified by baseline HRT use, hysterectomy or BMI. Oophorectomy was associated with increased rate of colorectal cancer, with highest rates among women with bilateral oophorectomy.