Ultraviolet radiation and skin cancer risk in offshore workers.

BACKGROUND: Excess skin cancer mortality and incidence have been reported among both land-based and offshore petroleum workers. The association between skin cancer and ultraviolet radiation (UVR) exposure has not been examined in these workers, although they have long off-duty periods and high average income that may allow travelling to sunny destinations. In addition, they have access to solariums free of charge on many accommodation platforms. AIMS: To prospectively examine risk of incident cutaneous melanoma (CM) and non-melanoma skin cancer (NMSC), according to sun-tanning habits with adjustment for aromatic hydrocarbon exposure. METHODS: A cohort of men employed offshore from 1965 to 1999 was linked through the Cancer Registry of Norway 1999-2012. Cox regression adapted to a stratified case-cohort design was used to estimate hazard ratios with 95% confidence intervals. RESULTS: The cohort included 24917 men. During 13.5 years of follow-up, 112 CMs and 70 NMSCs occurred. A positive dose-response relationship was seen between sunburn frequency and risk of CM (Ptrend < 0.05) and NMSC (Ptrend < 0.01). Solarium use both before and after age 20 was related to increased risk of NMSC. Sunscreen use was associated with increased risk of NMSC (Ptrend < 0.001). CONCLUSIONS: UVR exposure seems to be a significant contributor to the elevated risk of skin cancer observed in North Sea offshore workers. The positive association between solarium use and NMSC risk adds to the growing body of literature on artificial UV devices as carcinogenic.

A combination of low serum concentrations of vitamins K1 and D is associated with increased risk of hip fractures in elderly Norwegians: a NOREPOS study.

UNLABELLED: The present study investigated the risk of incident hip fractures according to serum concentrations of vitamin K1 and 25-hydroxyvitamin D in elderly Norwegians during long-term follow-up. The results showed that the combination of low concentrations of both vitamin D and K1 provides a significant risk factor for hip fractures. INTRODUCTION: This case-cohort study aims to investigate the associations between serum vitamin K1 and hip fracture and the possible effect of 25-hydroxyvitamin D (25(OH)D) on this association. METHODS: The source cohort was 21,774 men and women aged 65 to 79 years who attended Norwegian community-based health studies during 1994-2001. Hip fractures were identified through hospital registers during median follow-up of 8.2 years. Vitamins were determined in serum obtained at baseline in all hip fracture cases (n = 1090) and in a randomly selected subcohort (n = 1318). Cox proportional hazards regression with quartiles of serum vitamin K1 as explanatory variable was performed. Analyses were further performed with the following four groups as explanatory variable: I: vitamin K1 ≥ 0.76 and 25(OH)D ≥ 50 nmol/l, II: vitamin K1 ≥ 0.76 and 25(OH)D < 50 nmol/l, III: vitamin K1 < 0.76 and 25(OH)D ≥ 50 nmol/l, and IV: vitamin K1 < 0.76 and 25(OH)D < 50 nmol/l. RESULTS: Age- and sex-adjusted analyses revealed an inverse association between quartiles of vitamin K1 and the risk of hip fracture. Further, a 50 % higher risk of hip fracture was observed in subjects with both low vitamin K1 and 25(OH)D compared with subjects with high vitamin K1 and 25(OH)D (HR 1.50, 95 % CI 1.18-1.90). The association remained statistically significant after adjusting for body mass index, smoking, triglycerides, and serum α-tocopherol. No increased risk was observed in the groups low in one vitamin only. CONCLUSION: Combination of low concentrations of vitamin K1 and 25(OH)D is associated with increased risk of hip fractures.

Benzene exposure and risk of lymphohaematopoietic cancers in 25 000 offshore oil industry workers.

BACKGROUND: The aim of this work was to examine the risk of lymphohaematopoietic (LH) cancer according to benzene exposure among offshore workers. METHODS: Cancer registry data were used to identify 112 cancer cases diagnosed during 1999-2011 in a cohort of 24 917 Norwegian men reporting offshore work between 1965 and 1999. Analyses were conducted according to a stratified case-cohort design with a reference subcohort of 1661 workers. Cox regression was used to estimate hazard ratios with 95% confidence intervals, adjusted for other benzene exposure and smoking. RESULTS: Most workers were exposed to benzene for <15 years. The upper range values of average intensity and cumulative exposure were estimated to 0.040 p.p.m. and 0.948 p.p.m.-years, respectively. Risks were consistently elevated among exposed workers for all LH cancers combined and for most subgroups, although case numbers were small and yielded imprecise risk estimates. There was evidence of dose-related risk patterns according to cumulative exposure for acute myeloid leukaemia (AML), multiple myeloma (MM) (P trends 0.052 and 0.024, respectively), and suggestively so for chronic lymphocytic leukaemia (CLL) according to average intensity (P trend 0.094). CONCLUSIONS: Our results support an association between cumulative and intensity metrics of low-level benzene exposure and risk for AML, MM, and suggestively for CLL.

Low serum concentrations of alpha-tocopherol are associated with increased risk of hip fracture. A NOREPOS study.

UNLABELLED: We investigated the risk of hip fracture according to circulating alpha-tocopherol, a plant-derived substance with antioxidant properties, in community-dwelling older Norwegians. We found a linear increasing risk of hip fracture with lower serum alpha-tocopherol concentrations, with a 51% higher risk in the lowest compared to the highest quartile. INTRODUCTION: Oxidative stress is a suggested contributing cause of osteoporosis and fractures. Vitamin E (α-tocopherol) has potent antioxidant properties in humans. The relationship between circulating α-tocopherol and fracture risk is not established. The aim of this study was to investigate the association between serum α-tocopherol concentrations and risk of hip fracture during up to 11 years of follow-up. METHODS: We performed a case-cohort analysis among 21,774 men and women aged 65-79 years who participated in four community-based health studies in Norway 1994-2001. Serum α-tocopherol concentrations at baseline were determined in 1,168 men and women who subsequently suffered hip fractures (median follow-up 8.2 years) and in a random sample (n = 1,434) from the same cohort. Cox proportional hazard regression adapted for gender-stratified case-cohort data was performed. RESULTS: Median (25, 75 percentile) serum α-tocopherol was 30.0 (22.6, 38.3) µmol/L, and it showed a linear inverse association with hip fracture: hazard ratio (HR) 1.11 (95% confidence interval (CI) 1.04-1.20) per 10-µmol/L decrease in serum α-tocopherol, adjusted for gender and study center. The lowest compared to the highest quartile conferred an HR of 1.51 (95% CI 1.17-1.95), adjusted for gender and study center. Adjustment for smoking, month of blood sample, BMI, education, physical inactivity, self-rated health, and serum 25-hydroxyvitamin D (25(OH)D) yielded similar results. Taking serum total cholesterol concentration into account attenuated the association somewhat: HR of hip fracture was 1.37 (95% CI 1.05-1.77) in first versus fourth quartile of serum α-tocopherol/total cholesterol ratio. CONCLUSIONS: Low serum concentrations of α-tocopherol were associated with increased risk of hip fracture in older Norwegians.

Procollagen type 1 amino-terminal propeptide (P1NP) and risk of hip fractures in elderly Norwegian men and women. A NOREPOS study.

The current study aimed to assess a possible association between the bone turnover marker procollagen type 1 amino-terminal propeptide (P1NP) and future hip fractures in elderly Norwegian men and women and to elucidate the relation between P1NP, bone mineral density and 25-hydroxyvitamin D (25(OH)D). Men and women aged 71 to 77 from two population based health studies in Norway (1999-2001) were followed for a median period of 7.3 years with respect to hip fractures. The study was designed as a case-cohort study. P1NP and 25(OH)D were analysed in frozen serum samples obtained at baseline in hip fracture patients (n=340) and in randomly selected sex stratified sub-cohorts. Bone mineral density was measured by dual-energy X-ray absorptiometry (DXA) in a subset of participants. Cox proportional hazards regression with inverse probability weighting and robust variance was performed. No significant correlation between 25(OH)D and P1NP was found. A negative correlation between P1NP and BMD was observed in women (Rho=-0.36, p=0.001). A similar trend was observed in men. No association between quartiles of P1NP and rate of subsequent hip fractures was found. Spline analyses suggested a higher rate of hip fracture at P1NP levels above 60 µg/L in both men and women. A higher hip fracture rate, which was independent of BMD, was also indicated in women with very low levels of P1NP.

Hypertensive disorders in pregnancy and fetal death at different gestational lengths: a population study of 2 121 371 pregnancies.

OBJECTIVE: To compare the proportion of offspring that was stillborn in pregnancies with pre-eclampsia, gestational hypertension or chronic hypertension with those in normotensive pregnancies. DESIGN: Register-based observational study. SETTING: The Medical Birth Registry of Norway. POPULATION: All singleton births after 20 completed weeks of gestation in Norway from 1967 to 2006 (n = 2 121 371). METHODS: The proportion of stillborn offspring was estimated in normotensive pregnancies, and in pregnancies with pre-eclampsia, gestational and chronic hypertension at different gestational lengths. In addition, changes in the proportions of stillborn offspring by maternal hypertensive disorder from 1967-1986 to 1987-2006 were estimated. MAIN OUTCOME MEASURES: Fetal death. RESULTS: The prevalence of hypertensive disorders in pregnancy was 4.7%. In total, 17 933 fetal deaths occurred and 9.2% of these were in hypertensive pregnancies. In normotensive pregnancies, 0.8% (16 290/2 022 400) experienced fetal death. This was true for 1.9% (1170/62 261) of the pregnancies with pre-eclampsia, 1.2% (390/32 068) with gestational hypertension and 1.8% (83/4642) with chronic hypertension. There was a 44% overall reduction in fetal death rate from 1967-1986 to 1987-2006. The largest decline was in women with pre-eclampsia (80% reduction). In women with gestational hypertension and chronic hypertension, the overall reductions in fetal death rates were 49% and 57%, respectively, comparable with the 41% decline in normotensive pregnancies. CONCLUSIONS: In our nationwide study during 1967-2006, the risk of fetal death among women with hypertensive disorders in pregnancy has been greatly reduced, especially among pre-eclamptic women at term. The risk of fetal death among women with gestational or chronic hypertension has also decreased, but in a different manner.

The association of maternal age with placental weight: a population-based study of 536,954 pregnancies.

OBJECTIVE: To study the association of maternal age with placental weight, birthweight and placental weight/birthweight ratio. DESIGN: Population-based study. SETTING: Medical Birth Registry of Norway. POPULATION: All singleton births in Norway in the period 1999-2008 (n = 536,954). METHODS: Z-scores of placental weight and birthweight were calculated and divided into deciles. The proportions with a small or a large placenta were calculated within each maternal age group. Also, the odds ratios of having a small (lowest decile) and a large (highest decile) placenta, according to maternal age, were estimated, with and without adjustment for birthweight in grams, parity, smoking, pre-eclampsia and diabetes. MAIN OUTCOME MEASURES: Placental weight, birthweight and placental weight/birthweight ratio. RESULTS: The mean placental weight increased with maternal age: 647.1 g in women below the age of 20 years and 691.3 g in women aged 45 years or older. Among the oldest group of women (≥45 years) 15.8% of placentas were in the highest decile of placental weight z-score, whereas this was true for just 7.0% of women below the age of 20 years (Wald test, P < 0.001). Using women younger than 20 years of age as a reference, the odds ratio for having a placenta in the highest decile of placental weight z-score was 2.50 (95% CI 1.92-3.26) for women aged 45 years or older, after adjustment for offspring birthweight, parity, maternal smoking, pre-eclampsia and diabetes. CONCLUSION: We found an association between increased placental weight and maternal age, and this finding may be important in understanding the causes of adverse events associated with high maternal age.

Changes in fetal death during 40 years-different trends for different gestational ages: a population-based study in Norway.

OBJECTIVE: To study changes in gestational-age-specific fetal death risks during a 40-year period. DESIGN: Register-based observational study. SETTING: The Medical Birth Registry of Norway. POPULATION: All pregnancies after 16 weeks of gestation in Norway from 1967 to 2006 (n = 2, 182, 756). METHOD: Changes in fetal death risk since 1967-1971 (reference) were estimated as absolute risks (rates) and relative risks (RR) in ongoing pregnancies at the following gestational weeks; 16-22, 23-29, 30-36 and 37-43. MAIN OUTCOME MEASURES: Fetal death. RESULTS: In all pregnancies lasting longer than 22 weeks, the fetal death rate decreased during 1967-2006. The greatest decline was in term pregnancies (37-43 weeks) from 10.8 to 3.3 fetal deaths per 1000 at risk (crude RR 0.35; 95% CI 0.31-0.38) comparing 1967-1971 with 2002-2006. In pregnancies at 30-36 weeks the fetal death rate declined from 4.5 to 1.1 per 1000 (crude RR 0.23; 95% CI 0.21-0.26). At 23-29 weeks, the rate declined from 2.8 to 1.3 per 1000 (crude RR 0.46; 95% CI 0.40-0.52). An opposite trend was observed at early gestation (16-22 weeks) with an increase from 1.7 to 3.4 fetal deaths per 1000 ongoing pregnancies (crude RR 2.05; 95% CI 1.84-2.27). Adjustments for maternal age, parity, multiple pregnancies, paternal age and pre-eclampsia did not significantly alter the estimated associations. CONCLUSION: Since 1967 the risk of fetal death has been reduced by almost 70% in pregnancies lasting longer than 22 weeks; however, at 16-22 weeks of gestation there was an increase in risk. The causes of this increase should be further explored because it may be attributed to an increase in early delivery caused by the increased proportion of women being treated with cervical cone excision before pregnancy.

Maternal human parvovirus B19 infection and the risk of fetal death and low birthweight: a case-control study within 35 940 pregnant women.

OBJECTIVES: To assess the association between maternal parvovirus B19 infection and fetal death, birthweight and length of gestation. DESIGN: Case-control study. SETTING: Population based. POPULATION: Cases were all 281 women with fetal death within a cohort of 35 940 pregnant woxmen in Norway. The control group consisted of a random sample of 957 women with a live born child. METHOD: Information on pregnancy outcome was obtained from the Medical Birth Registry of Norway. First trimester serum samples were tested for antibodies against parvovirus B19 (IgM and IgG). In seronegative women, further serum was analysed to detect seroconversion during pregnancy. MAIN OUTCOME MEASURES: Fetal death, length of gestation and birthweight. RESULTS: Two of 281 (0.7%) of the women who experienced fetal death and nine of 957 (0.9%) of the controls had presence of IgM antibodies, crude odds ratio 0.8; 95% CI (0.2-3.5). In initially, seronegative women, 3.1% (2/65) with fetal death and 2.6% (8/307) with a live birth seroconverted, crude odds ratio 1.2; 95% CI (0.2-5.7). Presence of maternal parvovirus-specific IgG or IgM antibodies in the first trimester, or seroconversion during pregnancy were not associated with lower birthweight or reduced length of gestation in live born children, but was associated with low birthweight in stillborn offspring. CONCLUSION: Maternal parvovirus B19 infection was not associated with fetal death in our study. Very few cases of fetal death may be attributed to maternal parvovirus B19 infection.

A short matrix-version of the Edinburgh Depression Scale.

OBJECTIVE: Given the importance of depression as a world health problem, depression assessment should be standard practice in large-scale health surveys. The aim of the study was to construct a short matrix-version of the Edinburgh Depression Scale (EDS) that can be used in questionnaire studies. METHOD: On the basis of the complete EDS scale of ten items, answered by 2730 women, stepwise multiple regression analysis was used to find the combination of items that explains the maximum proportion of the variance of the full scale sum score. The selected EDS items were thereafter correlated with the Hopkins Symptom Check List (SCL-25) for external validation. RESULTS: The sum of five selected items from the EDS correlated at r = 0.96 with the full version. The EDS-5 scores correlated strongly with the SCL-25 (r = 0.75). CONCLUSION: The EDS-5 version shows good psychometric properties and may, for some scientific purposes, substitute the full EDS scale.

Association between level of physical activity and lung function among Norwegian men and women: the HUNT study.

OBJECTIVE: To estimate the association between level of physical activity in 1984-1986 and 1995-1997 and lung function in 1995-1997 among Norwegian men and women aged 28-80 years. DESIGN: In 1984-1986 and 1995-1997, all residents of Nord-Trøndelag County, Norway, aged > or =20 years were invited to participate in the Nord-Trøndelag Health Studies. These analyses included a sample that took part in both studies and underwent spirometry (n = 8047). We used linear regression models adjusting for potential confounders stratified by sex and age groups (28-49 years, 50-69 years and > or =70 years) to estimate the association between forced expiratory volume in 1 second (FEV1) and physical activity. RESULTS: Men and women who were physically active in 1985 and 1995 had the highest lung function in both sexes and in all age groups. The reduction in FEV1 ranged from 20 ml to 170 ml, similar to 1-7% of predicted values dependent on physical activity level. Lung function was also associated with body mass index (BMI), height, smoking and subjective health. CONCLUSIONS: The findings show that a high level of physical activity corresponds to about 3-5 years of normal decline in FEV1 (30 ml/year), and may therefore overcome the disadvantages of a decline in FEV1 from increasing age.

A simple correction for ties when censoring times depend on covariates.

We point out that the conventional methods for ties correction may be seriously biased when censoring times depend on covariates. A simple modification to the Efron correction method is suggested which works remarkably well in simulation studies. The method corresponds closely to breaking ties by random ordering. The modified correction method is easy to implement and computationally no more demanding than the Efron correction.

Cesarean delivery and cow milk allergy/intolerance.

The present study provides support for a positive association between cesarean delivery and persistent cow milk allergy/cow's milk intolerance. Correspondingly, a negative association was seen between cesarean delivery and early outgrown cow milk allergy/intolerance. A possible explanation is that cesarean delivery, rather than increasing the overall risk of food allergy, increases the risk of persistency of disease among food allergic children.

Feasibility of measuring lung function in preschool children.

BACKGROUND: There have been difficulties in applying spirometric tests to children of preschool age. METHODS: The feasibility of measuring lung function was examined in 652 children aged 3-6 years using dynamic spirometry with an animation programme and the guidelines approved by the European Respiratory Society. RESULTS: Data from 603 (92%) children with at least two acceptable forced expiratory manoeuvres were analysed; 408 (68%) achieved at least three acceptable manoeuvres. Children with only two acceptable manoeuvres were younger, shorter, and weighed less (p<0.001). The lower levels of lung function in this group were partly explained by body size. 63% of those with three acceptable manoeuvres had a difference of

Depression in postpartum and non-postpartum women: prevalence and risk factors.

OBJECTIVE: The aim of the study was to assess the prevalence of depression in postpartum women as compared with non-postpartum women, and to identify risk factors of depression in both groups. METHOD: A population based questionnaire study was performed among women 18-40 years in two municipalities in Norway in 1998-1999. A total of 2,730 women were included, of whom 416 were in the postpartum period. RESULTS: The prevalence of depression was higher in non-postpartum as compared with postpartum women. High scores on the life event scale, a history of depression and a poor relationship to the partner were associated with depression in both postpartum and non-postpartum women. When controlling for the identified risk factors of depression the odds-ratio for depression in the postpartum period was 1.6 (95% CI: 1.0-2.6). CONCLUSION: The risk for depression was increased in the postpartum period, when controlling for the uneven distribution of risk factors.

Review of validation studies of the Edinburgh Postnatal Depression Scale.

OBJECTIVE: To review validation studies of the Edinburgh Postnatal Depression Scale (EPDS). METHOD: A systematic search was performed in Medline and the Science Citation Index Expanded (ISI) from the period 1987-2000. For sensitivity and specificity of the EPDS presented in each study, 95% confidence intervals were estimated. Positive and negative predictive values were estimated assuming prevalences of postpartum depression ranging from 5% to 20%. RESULTS: Eighteen validation studies were identified. The study design varied between studies. The sensitivity and specificity estimates also varied: 65-100% and 49-100%, respectively. The confidence intervals were estimated to be wide. Our estimates suggest a lower positive predictive value in a normal population than in the validation study samples. CONCLUSION: Most studies show a high sensitivity of the EPDS. Because of the differences in study design and large confidence intervals, uncertainty remains regarding the comparability between the sensitivity and specificity estimates of the different EPDS versions.

Changing paternity and time since last pregnancy; the impact on pre-eclampsia risk. A study of 547 238 women with and without previous pre-eclampsia.

BACKGROUND: Long time interval between pregnancies has been found to increase the risk of pre-eclampsia in second pregnancy. Our aim was to investigate whether this effect is influenced by a history of pre-eclampsia or a change in paternity. METHODS: We studied 547 238 women with a first and second pregnancy registered in the Medical Birth Registry of Norway, 1967-1998. The relative risk of pre-eclampsia in the second delivery according to time interval between deliveries was estimated as odds ratios (OR) in logistic regression models, controlling for changing paternity, maternal age and calendar time period in women with and without previous pre-eclampsia. RESULTS: A change of paternity for the second pregnancy was associated with a reduced risk of pre-eclampsia after controlling for the time since first delivery (adjusted OR = 0.80, 95% CI : 0.72-0.90), but the interaction between change in paternity and time between deliveries was significant only for women with no previous pre-eclampsia. The interaction between history of pre-eclampsia and time interval between the two deliveries was highly significant, and for women with no previous pre-eclampsia the risk of pre-eclampsia in second pregnancy increased with increasing time interval (for intervals longer than 15 years the adjusted OR was 2.11, 95% CI : 1.75-2.53). For women with previous pre-eclampsia the risk tended to decrease with increasing time interval between deliveries. CONCLUSIONS: The protective impact of a new father for the second pregnancy challenges the hypothesis of primipaternity, and implies that the increase in pre-eclampsia risk ascribed to new father by others is due to insufficient control for interpregnancy interval.

Symptoms of anxiety and depression among mothers of pre-school children: effect of chronic strain related to children and child care-taking.

BACKGROUND: Factors that affect maternal mental health were studied when the children were 30 and 50 months old, and changes in the importance of these factors over time were analyzed. A specific aim was to elucidate the role of chronic strain related to children and child care-taking. This study follows up previous work on the influence of social class, strain and social support on maternal mental distress when the children were 18 months old. METHODS: The sample is population based, and 1,081 parents were invited to fill out questionnaires. Maternal mental distress was measured by the Hopkins Symptom Checklist (SCL-25). Multiple regression analyses were conducted at each time point and chi-square tests were used to analyze the changes between the estimated regression coefficients over time. RESULTS: Chronic strain related to children and child care-taking consistently predicted maternal mental distress. Among the specific child related strains, problems with child care-taking were significantly associated with maternal symptom levels at all time points. The importance of two specific child problem behaviors (activity level and the child being a worrier) on maternal mental health changed over time. LIMITATIONS: Conclusions about causality can not be drawn based on cross-sectional analyses. The self-report measures used here may be biased by the current mood state. CONCLUSIONS: Problems with child care arrangements and combining work and child care-taking are predictive of maternal mental health when the children are 18, 30 and 50 months old. The risk and protective factors found here may have implications for prevention and intervention.