Menopausal hormone therapy, oral contraceptives and risk of chronic low back pain: the HUNT Study.

BACKGROUND: There are indications that use of menopausal hormone therapy (MHT) and oral contraceptives (OC) increases the risk of low back pain (LBP), with higher oestrogen levels involved in the underlying mechanisms. The purpose of the present study was to investigate associations between use of systemic MHT or OC and risk of chronic LBP in a large population-based data set. METHODS: Data were obtained from two surveys in the Trøndelag Health Study in Norway, HUNT2 (1995-1997) and HUNT3 (2006-2008). A cross-sectional study of association between use of systemic MHT and prevalence of chronic LBP comprised 12,974 women aged 40-69 years in HUNT2, with 4007 women reporting chronic LBP. A cohort study involving MHT comprised 6007 women without chronic LBP at baseline in HUNT2, and after 11 years 1245 women reported chronic LBP at follow-up in HUNT3. The cross-sectional study of association with use of OC included 23,593 women aged 20-69 years in HUNT2, with 6085 women reporting chronic LBP. The corresponding cohort study included 10,586 women without chronic LBP at baseline in HUNT2, of whom 2084 women reported chronic LBP in HUNT3. Risk of chronic LBP was examined in both study designs in generalised linear models with adjustment for potential confounders. RESULTS: In the cohort study, current users of systemic MHT at baseline showed a greater risk of chronic LBP (relative risk (RR) 1.30; 95% CI: 1.14-1.49; compared with never users). The risk increased according to duration of MHT use (P for linear trend = 0.003). Known users of systemic MHT based exclusively on oestrogen experienced the highest risk (RR 1.49; 95% CI: 1.16-1.91), but an increased risk was also seen among known users of oestrogen-progestin combination MHT (RR 1.35; 95% CI: 1.16-1.57). A slight increase in risk of chronic LBP was found in the cohort study among former users of OC (RR 1.17; 95% CI: 1.06-1.30; compared with never users). CONCLUSIONS: Long-lasting use of systemic MHT, in particular therapy based on oestrogen only, is associated with greater risk of chronic LBP. Having been a user of OC most likely entails a minor increase in risk.

Socioeconomic and geographic differences in ablation of atrial fibrillation in Norway - a national cohort study.

BACKGROUND: The aim of this study was to analyse whether there are patient related or geographic differences in the use of catheter ablation among atrial fibrillation patients in Norway. METHODS: National population-based data on individual level of all Norwegians aged 25 to 75 diagnosed with atrial fibrillation from 2008 to 2017 were used to study the proportion treated with catheter ablation. Survival analysis, by Cox regression with attained age as time scale, separately by gender, was applied to examine the associations between ablation probability and educational level, income level, place of residence, and follow-up time. RESULTS: Substantial socioeconomic and geographic variation was documented. Atrial fibrillation patients with high level of education and high income were more frequently treated with ablation, and the education effect increased with increasing age. Patients living in the referral area of St. Olavs Hospital Trust had around three times as high ablation rates as patients living in the referral area of Finnmark Hospital Trust. CONCLUSIONS: Differences in health literacy, patient preference and demands are probably important causes of socioeconomic variation, and studies on how socioeconomic status influences the choice of treatment are warranted. Some of the geographic variation may reflect differences in ablation capacity. However, geographic variation related to differences in clinical practice and provider preferences implies a need for clearer guidelines, both at the specialist level and at the referring level.

Equitable access to cancer patient pathways in Norway - a national registry-based study.

BACKGROUND: In 2015, cancer patient pathways (CPP) were implemented in Norway to reduce unnecessary non-medical delay in the diagnostic process and start of treatment. The main aim of this study was to investigate the equality in access to CPPs for patients with either lung, colorectal, breast or prostate cancer in Norway. METHODS: National population-based data on individual level from 2015 to 2017 were used to study two proportions; i) patients in CPPs without the cancer diagnosis, and ii) cancer patients included in CPPs. Logistic regression was applied to examine the associations between these proportions and place of residence (hospital referral area), age, education, income, comorbidity and travel time to hospital. RESULTS: Age and place of residence were the two most important factors for describing the variation in proportions. For the CPP patients, inconsistent differences were found for income and education, while for the cancer patients the probability of being included in a CPP increased with income. CONCLUSIONS: The age effect can be related to both the increasing risk of cancer and increasing number of GP and hospital contacts with age. The non-systematic results for CPP patients according to income and education can be interpreted as equitable access, as opposed to the systematic differences found among cancer patients in different income groups. The inequalities between income groups among cancer patients and the inequalities based on the patients' place of residence, for both CPP and cancer patients, are unwarranted and need to be addressed.

Associations between the number of children, age at childbirths and prevalence of chronic low back pain: the Nord-Trøndelag Health Study.

BACKGROUND: Associations between childbirths and subsequent risk of low back pain (LBP) have not been clarified. Changes in sex hormone levels or lumbar posture during pregnancy may have an impact on LBP later in life. The purpose of this study was to explore associations between the number of childbirths, age at childbirths and prevalence of chronic LBP in a general population of women. METHODS: Data were obtained from the Norwegian community-based Nord-Trøndelag Health Study, HUNT2 (1995-1997). Women aged 20-69 years indicated whether they suffered from chronic LBP, defined as LBP persisting at least 3 months continuously during last year. Information about LBP was collected from 3936 women who had experienced no childbirths, 3143 women who had delivered one child only and 20,584 women who had delivered 2 or more children. Of these, 7339 women reported chronic LBP. The 595 women who were pregnant when information was collected were considered separately, regardless of previous births, with 80 women reporting chronic LBP. Associations with prevalence of chronic LBP were examined by generalised linear modelling with adjustment for potential confounders in a cross-sectional design. RESULTS: Women who had delivered one child only showed a higher prevalence of chronic LBP than women with no childbirths (prevalence ratio (PR) 1.11; 95% CI: 1.01-1.22). Among women with one or more childbirths, no overall change in prevalence could be demonstrated with an increasing number of children in analyses adjusted for age at first delivery. In women with at least two childbirths, an age less than 20 years at first childbirth was associated with an increased prevalence of chronic LBP (PR 1.36; 95% CI: 1.25-1.49; compared with age 25-29 years). No association was observed between age at last delivery and chronic LBP. The lowest prevalence of chronic LBP was found among women who were currently pregnant (PR 0.80; 95% CI: 0.63-1.00; compared with women with no childbirths). CONCLUSIONS: Having experienced at least one childbirth seems to be associated with a higher prevalence of chronic LBP later in life. A young age at first childbirth is also associated with a long-lasting increased prevalence.

Modelling memory decay after injuries using household survey data from Khartoum State, Sudan.

BACKGROUND: Injuries represent an important cause of morbidity and mortality worldwide. In retrospective epidemiological studies, estimated rates of reported injuries often decline considerably when information is included from periods more than a few months before the data collection. Such low rates are usually regarded as a consequence of memory decay. It is largely unknown whether the extent of memory decay depends on external factors otherwise affecting injury rates. METHODS: A statistical model was introduced to separate the influence of external factors on true injury rates from effects on memory decay. The relationship between apparent rates and time elapsed between injury occurrence and data collection was described by a parametric regression model. Relationships between memory decay and external factors were modelled by effect modification of the relationship with time. The procedure was applied to data collected in a retrospective household survey, carried out in Khartoum State in 2010, which elicited information about injuries that had occurred during the last year. The survey included 5661 individuals in 973 households, reporting a total of 481 non-fatal injuries. RESULTS: In the data from Khartoum State, differences in memory recall were observed between socioeconomic groups, with considerably faster memory decay in the lower socioeconomic tertile. In this tertile the estimated probability that an injury which occurred 6 months ago was reported was only 18%, compared to probabilities of about 35% in the remainder of the population. In the lower socioeconomic tertile, in contrast to other groups, a simple exponential model was not sufficient for describing memory decay. Memory decay did not depend on sex, age, urban/rural status or education. Road traffic injuries were subject to less memory decay than injuries due to falls, mechanical causes and burns. Memory decay seriously affected crude overall injury rates and also to some degree estimated relative rates. CONCLUSION: In the statistical analysis of retrospective injury data it is important to take into account the effects of memory decay.

Is there a U-shaped relationship between physical activity in leisure time and risk of chronic low back pain? A follow-up in the HUNT Study.

BACKGROUND: Physical activity in leisure time is often considered to have favourable effects on the risk of low back pain (LBP), but demonstrating a definite association in epidemiological studies has proven difficult. The purpose of the present study was to explore associations between physical activity and risk of chronic LBP in an adult population and to investigate whether relationships are limited to certain age groups or to females or males. A particular objective was to determine whether support could be found for a U-shaped relationship, with both low and high activity levels carrying greater risk. METHODS: The relationship between physical activity and risk of chronic LBP was examined in a Norwegian prospective study using data from the community-based HUNT2 and HUNT3 surveys. Participants were 9616 women and 8452 men without LBP at baseline, who reported after 11 years whether they suffered from LBP. Associations between baseline physical activity in leisure time and risk of chronic LBP at end of follow-up were evaluated by generalized linear modelling with adjustment for potential confounders. RESULTS: Significant associations between leisure time physical activity and risk were observed in both sexes after age adjustment, mainly suggesting inverse relationships. Women participating in hard physical activity 1-2 h per week had a relative risk (RR) of chronic LBP of 0.81 (95 % CI 0.71-0.93) compared to those with only light physical activity less than 1 h per week. The corresponding RR in men was 0.71 (95 % CI 0.60-0.85). After adjustment for education, employment, occupational activity, body mass index (BMI) and smoking, significant relationships could only be demonstrated in those aged 50 years or more at baseline. The associations differed between female educational groups, with more U-shaped relationships being observed among women with basic education only. CONCLUSION: No strong support was found overall for U-shaped relationships. However, no further general decrease in risk was seen among those with 3 h or more of hard physical activity per week. The contrasts observed between female educational groups may reflect different preferences regarding specific strenuous activities. Men aged 50 years or more seem in particular to benefit from hard physical activities.

Socioeconomic and disability consequences of injuries in the Sudan: a community-based survey in Khartoum State.

BACKGROUND: Fatal and non-fatal injuries are of increasing public health concern globally, particularly in low and middle-income countries. Injuries sustained by individuals also impact society, creating a loss of productivity with serious economic consequences. In Sudan, there is no documentation of the burden of injuries on individuals and society. METHODS: A community-based survey was performed in Khartoum State, using a stratified two-stage cluster sampling technique. Households were selected in each cluster by systematic random sampling. Face-to-face interviews during October and November 2010 were conducted. Fatal injuries occurring during 5 years preceding the survey and non-fatal injuries occurring during 12 months preceding interviews were included. RESULTS: The total number of individuals included was 5661, residing in 973 households. There were 28 deaths due to injuries out of a total of 129 reported deaths over 5 years. A total of 441 cases of non-fatal injuries occurred during the 12 months preceding the survey. The number of disability days differed significantly between mechanisms of injury. Road traffic crashes and falls caused the longest duration of disability. Men had a higher probability than women of losing a job due to an injury. CONCLUSIONS: This study demonstrates the importance of prioritising prevention of road traffic crashes and falls. The loss of productivity in lower socioeconomic strata highlights the need for social security policies. Further research is needed for estimating the economic cost of injuries in Sudan.

Improving the error rates of the Begg and Mazumdar test for publication bias in fixed effects meta-analysis.

BACKGROUND: The rank correlation test introduced by Begg and Mazumdar is extensively used in meta-analysis to test for publication bias in clinical and epidemiological studies. It is based on correlating the standardized treatment effect with the variance of the treatment effect using Kendall's tau as the measure of association. To our knowledge, the operational characteristics regarding the significance level of the test have not, however, been fully assessed. METHODS: We propose an alternative rank correlation test to improve the error rates of the original Begg and Mazumdar test. This test is based on the simulated distribution of the estimated measure of association, conditional on sampling variances. Furthermore, Spearman's rho is suggested as an alternative rank correlation coefficient. The attained level and power of the tests are studied by simulations of meta-analyses assuming the fixed effects model. RESULTS: The significance levels of the original Begg and Mazumdar test often deviate considerably from the nominal level, the null hypothesis being rejected too infrequently. It is proven mathematically that the assumptions for using the rank correlation test are not strictly satisfied. The pairs of variables fail to be independent, and there is a correlation between the standardized effect sizes and sampling variances under the null hypothesis of no publication bias. In the meta-analysis setting, the adverse consequences of a false negative test are more profound than the disadvantages of a false positive test. Our alternative test improves the error rates in fixed effects meta-analysis. Its significance level equals the nominal value, and the Type II error rate is reduced. In small data sets Spearman's rho should be preferred to Kendall's tau as the measure of association. CONCLUSIONS: As the attained significance levels of the test introduced by Begg and Mazumdar often deviate greatly from the nominal level, modified rank correlation tests, improving the error rates, should be preferred when testing for publication bias assuming fixed effects meta-analysis.

Lipid Levels During Adult Lifetime in Men and Women With and Without a Subsequent Incident Myocardial Infarction: A Longitudinal Analysis of Data From the Tromsø Study 1974 to 2016.

Background The atherosclerotic effect of an adverse lipid profile is assumed to accumulate throughout life, leading to increased risk of myocardial infarction (MI). Still, little is known about age at onset and duration of unfavorable lipid levels before MI. Methods and Results Longitudinal data on serum lipid levels for 26 130 individuals (50.5% women, aged 20-89 years) were obtained from 7 population-based health surveys in Tromsø, Norway. Diagnoses of MI were obtained from national registers. A linear mixed model was applied to compare age- and sex-specific mean values of total cholesterol, high-density lipoprotein cholesterol (HDL-C), and triglyceride concentration by MI status (MI versus non-MI). Already from young adulthood, 20 to 35 years before the incident MI, individuals with a subsequent incident MI had on average more adverse lipid levels than individuals of the same age and sex without MI. Analogous to a dose-response relationship, there was a clear trend toward more severe adverse lipid levels the lower the age at incident MI (P<0.001, test for trend through ordered categories <55, 55-74, ≥75 years). This trend was particularly pronounced for high-density lipoprotein cholesterol in percentage of total cholesterol (both sexes) and for the relative relationship between triglyceride, high-density lipoprotein cholesterol, and total cholesterol level (women). The difference in mean lipid level by MI status was just as large in women as in men, but the age pattern differed (P≤0.05, tests of 3-way interaction). Conclusions Compared with general population mean levels, adverse lipid levels were seen 20 to 35 years before the incident MI in both men and women.

Does the risk of chronic low back pain depend on age at menarche or menopause? A population-based cross-sectional and cohort study: the Trøndelag Health Study.

OBJECTIVE: In most population-based studies of low back pain (LBP), women have a higher risk than men, possibly reflecting hormonal influences. The aim of this study was to explore associations between age at menarche and menopause and risk of chronic LBP. DESIGN: Population-based cross-sectional and cohort study designs. SETTING: The HUNT2 and HUNT3 medical surveys of the entire population of Nord-Trøndelag County in Norway. MAIN OUTCOME MEASURE: Prevalence or risk of chronic LBP, defined as LBP persisting at least 3 months continuously during last year. PARTICIPANTS: Associations between age at menarche and prevalence of chronic LBP were examined in cross-sectional data from HUNT2, comprising 27 697 women aged 20-69 years, with 7300 women reporting LBP. The corresponding cohort data included 11 659 women without LBP at baseline in HUNT2, with 2353 women reporting LBP at follow-up 11 years later in HUNT3. Cross-sectional data on age at menopause or premenopausal status included 11 332 women aged 40-69 years, with 3439 women reporting chronic LBP. Corresponding cohort data included 7893 women without LBP at baseline, of whom 1100 developed LBP. METHODS: Associations between age at menarche or menopause and risk of chronic LBP were examined by generalised linear modelling. RESULTS: A U-shaped association was indicated between age at menarche and risk of chronic LBP, both in the cross-sectional and cohort studies. Age at menarche ≤11 years was associated with an increased risk of chronic LBP, with a relative risk of 1.32 (95% CI 1.15 to 1.52), compared with age 14 years at menarche, after relevant adjustments. Corresponding cross-sectional crude absolute risks were 32% and 25%, respectively. No association was established between age at menopause and risk of LBP. Being premenopausal had no influence on risk. CONCLUSIONS: In contrast to results for age at menopause, the association with age at menarche suggests that hormonal factors affect the risk of LBP.

Impact of parents' education on variation in hospital admissions for children: a population-based cohort study.

OBJECTIVES: To assess the impact of parental educational level on hospital admissions for children, and to evaluate whether differences in parents' educational level can explain geographic variation in admission rates. DESIGN: National cohort study. SETTING: The 18 hospital referral areas for children in Norway. PARTICIPANTS: All Norwegian children aged 1-16 years in the period 2008-2016 and their parents. MAIN OUTCOME MEASURES: Age- and gender-adjusted admission rates and probability of admission. RESULTS: Of 1 538 189 children, 156 087 (10.2%) had at least one admission in the study period. There was a nearly twofold (1.9) variation in admission rates between the hospital referral areas (3113 per 100 000 children, 95% CI: 3056 to 3169 vs 1627, 95% CI: 1599 to 1654). Area level variances in multilevel analysis did not change after adjusting for parental level of education. Children of parents with low level of education (maternal level of education, low vs high) had the highest admission rates (2016: 2587, 95% CI: 2512 to 2662 vs 1810, 95% CI: 1770 to 1849), the highest probability of being admitted (OR: 1.18, 95% CI: 1.16 to 1.20), the highest number of admissions (incidence rate ratio: 1.05, 95% CI: 1.01 to 1.10) and admissions with lower cost (-0.5%, 95% CI: -1.2% to 0.3%). CONCLUSIONS: Substantial geographic variation in hospital admission rates for children was found, but was not explained by parental educational level. Children of parents with low educational level had the highest admission probability, and the highest number of admissions, but the lowest cost of admissions. Our results suggest that the variation between the educational groups is not due to differences in medical needs, and may be characterised as unwarranted. However, the manner in which health professionals communicate and interact with parents with different educational levels might play an important role.

Associations between serum lipid levels and chronic low back pain.

BACKGROUND: Low back pain may be related to abnormal lipid levels because of atherosclerosis in arteries supplying the lumbar region. METHODS: In the cross-sectional HUNT 2 study in the Norwegian county of Nord-Trøndelag, lipid levels were measured in 33,962 women and 30,031 men. A total of 8954 women (26%) and 6273 men (21%) reported suffering from low back pain continuously for at least 3 months in the past year. RESULTS: In age-adjusted analyses, the prevalence of low back pain was inversely associated with HDL cholesterol and positively associated with triglycerides, with stronger associations in women than in men. Relatively weak associations remained in women after adjustment for smoking, physical activity, education, work status, blood pressure, and body mass, but no associations remained among men. Total cholesterol levels were unrelated to low back pain in either sex after age adjustment. CONCLUSIONS: The results are partly consistent with the atherosclerosis hypothesis.

Histological type and grade of breast cancer tumors by parity, age at birth, and time since birth: a register-based study in Norway.

BACKGROUND: Some studies have indicated that reproductive factors affect the risk of histological types of breast cancer differently. The long-term protective effect of a childbirth is preceded by a short-term adverse effect. Few studies have examined whether tumors diagnosed shortly after birth have specific histological characteristics. METHODS: In the present register-based study, comprising information for 22,867 Norwegian breast cancer cases (20-74 years), we examined whether histological type (9 categories) and grade of tumor (2 combined categories) differed by parity or age at first birth. Associations with time since birth were evaluated among 9709 women diagnosed before age 50 years. Chi-square tests were applied for comparing proportions, whereas odds ratios (each histological type vs. ductal, or grade 3-4 vs. grade 1-2) were estimated in polytomous and binary logistic regression analyses. RESULTS: Ductal tumors, the most common histological type, accounted for 81.4% of all cases, followed by lobular tumors (6.3%) and unspecified carcinomas (5.5%). Other subtypes accounted for 0.4%-1.5% of the cases each. For all histological types, the proportions differed significantly by age at diagnoses. The proportion of mucinous and tubular tumors decreased with increasing parity, whereas Paget disease and medullary tumors were most common in women of high parity. An increasing trend with increasing age at first birth was most pronounced for lobular tumors and unspecified carcinomas; an association in the opposite direction was seen in relation to medullary and tubular tumors. In age-adjusted analyses, only the proportions of unspecified carcinomas and lobular tumors decreased significantly with increasing time since first and last birth. However, ductal tumors, and malignant sarcomas, mainly phyllodes tumors, seemed to occur at higher frequency in women diagnosed <2 years after first childbirth. The proportions of medullary tumors and Paget disease were particularly high among women diagnosed 2-5 years after last birth. The high proportion of poorly differentiated tumors in women with a recent childbirth was partly explained by young age. CONCLUSION: Our results support previous observations that reproductive factors affect the risk of histological types of breast cancer differently. Sarcomas, medullary tumors, and possible also Paget disease, may be particularly susceptible to pregnancy-related exposure.

Effects of a Parent-Administered Exercise Program in the Neonatal Intensive Care Unit: Dose Does Matter-A Randomized Controlled Trial.

BACKGROUND: Despite the risk of delayed motor development in infants born preterm, knowledge about interventions in the neonatal intensive care unitt (NICU) and the effects of dosing is sparse. OBJECTIVE: The objectives of this study were to examine the effectiveness of a parent-administered exercise program in the NICU on motor outcome at 3 months corrected age (CA) and the effect of dosing on motor performance. DESIGN: This was a randomized clinical trial. SETTING: The study was conducted at 3 university hospitals in Tromsø, Trondheim, and Oslo, Norway. PARTICIPANTS: A total of 153 infants with gestational age <32 weeks at birth were randomly assigned to intervention or control groups. INTERVENTION: A 3-week parent-administered intervention designed to facilitate movements in preterm infants was performed in the NICU. Parents were asked to administer the intervention 10 minutes twice a day. MEASUREMENTS: Test of Infant Motor Performance (TIMP) was used to assess short-term outcome at 3 months CA. RESULTS: No significant difference in the TIMP z-score was found between intervention and control groups at follow-up 3 months CA, but a significant positive relationship was found between total intervention dose and TIMP z-scores. The adjusted odds of having a clinical z-score < 0 at 3 months CA was about 6 times higher for infants with less than median intervention time than for infants with a longer intervention time. LIMITATIONS: The number of infants born before 28 weeks was small. A spillover effect in favor of the control group was possible. We do not know if the infants received physical therapy after discharge from the hospital. CONCLUSIONS: There was no difference in motor performance between the intervention group and the control group at 3 months CA. However, an increased intervention dose was positively associated with improved motor outcome.

Parity and time interval since childbirth influence survival in endometrial cancer patients.

Parity and time interval since last birth have been found to be associated with the risk of endometrial cancer, but few previous studies have examined whether these reproductive factors have prognostic impact. We examined this issue among 740 nulliparous and 3355 parous endometrial cancer patients diagnosed in Norway during the period 1961-1999. The mean age at diagnosis was 55.7 years (range, 25-74 years). Hazard ratios (HRs) with 95% confidence intervals were calculated in Cox proportional regression models. Parous women had significantly (P < 0.001) better prognosis than nulliparous women. In analyses adjusted for age at diagnosis, clinical stage, and histological type, the HR for parous versus nulliparous women was 0.68 (95% confidence interval, 0.57-0.82). The prognostic impact of parity was restricted to patients with endometrioid tumors (P = 0.014, test for interaction) and appeared to be most pronounced in women without metastases (P = 0.14, test for interaction). Moreover, the improved prognosis was strongest for women with the shortest time interval since last childbirth. The HRs (nulliparous women as reference) were 0.51, 0.60, and 0.80 for women less than 15, 15 to 24, and 25 years or more since birth (P < 0.001). The observed beneficial effect of pregnancies may be related to a strong exposure to progesterone during pregnancy. However, it is possible that tumors developing in nulliparous and parous women have different biological features. Further knowledge on this issue may provide valuable information that can be used for individualized treatment.

Prognostic impact of parity in 493 uterine sarcoma patients.

INTRODUCTION: Nulliparity has been found to negatively affect prognosis among endometrial cancer patients. Few previous studies have examined the prognostic impact of parity in patients with uterine sarcomas. METHODS: In the present nationwide, register-based study in Norway, we explore whether parity influences survival among 493 women diagnosed with malignant uterine sarcomas. Hazard ratios for total mortality were calculated in Cox proportional hazard regression analyses. RESULTS: The 5-year Kaplan-Meier survival rates for the 126 endometrial stromal sarcoma (ESS) patients, 249 leiomyosarcoma (LS) patients, and 118 carcinosarcoma (CS) patients were 74%, 68%, and 55%, respectively, but varied considerably by age at diagnosis and clinical stage. In the univariate analyses, nulliparous women had poorer prognosis than parous women among CS patients (P = 0.071, log-rank test) and ESS patients (P = 0.15). In analyses adjusted for clinical stage and age at diagnosis, nulliparity was associated with a worse outcome in ESS patients only (hazard ratio, 0.50; 95% confidence interval, 0.22-1.12; parous vs nulliparous women); a trend with increasing number of births was also observed, of borderline significance (P = 0.058). No independent prognostic impact of parity was found in LS or CS patients. However, a considerably higher proportion of nulliparous than parous CS patients was diagnosed with advanced-stage disease (P = 0.003). CONCLUSION: Nulliparity seems to be associated with poorer prognosis in ESS patients; no independent prognostic impact of parity was seen among LS or CS patients. Further knowledge on underlying biological mechanisms may be valuable for improved treatment.

Association of albuminuria and cancer incidence.

Albuminuria, which is associated with noncardiovascular mortality, might be a result of altered vascular permeability caused by cytokines and other tumor cell products. The aim of this population-based, longitudinal study was to examine whether elevated albumin-to-creatinine ratio (ACR) is associated with cancer incidence. A total of 5425 participants without diabetes or previous cancer in the Tromsø Study were followed; 590 had a first diagnosis of cancer during 10.3 yr of follow-up. The ACR at baseline significantly correlated with the incidence of cancer, even after adjustment for age, gender, body mass index, physical activity, and smoking (P < 0.001). Participants with ACR in the highest quintile were 8.3- and 2.4-fold more likely to receive a diagnosis of bladder cancer and lung cancer, respectively, compared with those with ACR in the lowest quintile after similar adjustments. It is concluded that albuminuria is associated with cancer incidence in individuals without a history of diabetes, macroalbuminuria, or previous cancer and that it might confer risks of varying magnitude for different types of cancer.

Does diabetes influence the probability of experiencing chronic low back pain? A population-based cohort study: the Nord-Trøndelag Health Study.

OBJECTIVE: Low back pain (LBP) is a major problem in modern society and it is important to study possible risk factors for this disorder. People with diabetes are often affected by LBP, but whether diabetes represents a risk factor for LBP has not been studied in detail. The aim of this study was to explore the association between diabetes and subsequent risk of chronic LBP. DESIGN: An 11-year follow-up study. SETTING: The Nord-Trøndelag Health Study (HUNT2; 1995-1997) and HUNT3 (2006-2008) surveys of Nord-Trøndelag County in Norway. MAIN OUTCOME MEASURE: Chronic LBP, defined as LBP persisting at least 3 months continuously during the last year. PARTICIPANTS: A total of 18 972 persons without chronic LBP at baseline in HUNT2, and 6802 persons who reported chronic LBP at baseline in HUNT2. METHODS: Associations between diabetes and risk of chronic LBP among individuals aged 30-69 years were examined by generalised linear modelling. RESULTS: Men without chronic LBP at baseline showed a significant association between diabetes and risk of chronic LBP (relative risk (RR) 1.43, 95% CI 1.04 to 1.96, p=0.043). In women, no association was found (RR 1.01, 95% CI 0.69 to 1.48, p=0.98). No association could be established between diabetes and recurrence or persistence of chronic LBP after 11 years in either sex. CONCLUSIONS: Men with a diagnosis of diabetes may have a higher risk of subsequently experiencing chronic LBP.

Twin births, sex of children and maternal risk of endometrial cancer: a cohort study in Norway.

OBJECTIVE: To explore whether twin births and sex of children influenced maternal risk of endometrial cancer, possibly with effect modification by age. DESIGN: Population-based prospective study. STUDY POPULATION: A total of 1,094,017 parous Norwegian women aged 30-74 years, including 3,356 endometrial cancer cases. Among the 27,158 mothers of twins, 101 cases occurred. METHODS: Incidence rate ratios (IRR) with 95% confidence intervals (CI) were calculated in Poisson regression analyses of person-years at risk. RESULTS: Women ever having experienced a twin birth had an overall higher risk of endometrial cancer than women with singleton births only (IRR=1.26, 95% CI=1.03-1.53). Women with twin boys appeared to be the main contributor to the overall elevated risk (IRR=1.57, 95% CI=1.15-2.14). The risk estimates for women with twin girls or sex-nonconcordant twins were close to unity (IRR of 1.09 and 1.12, respectively). However, age-specific analyses revealed an elevated risk also in women with twin girls, but only before age 55 years (IRR=1.92, 95% CI=1.27-2.89); a lower risk was seen at older ages (IRR=0.41, 95% CI=0.19-0.92). The risk estimates for twin boys and sex-nonconcordant twins were consistently observed across age groups. The effect modification by age was statistically significant (p=0.0024). No association was found with sex of children in singleton mothers. CONCLUSION: Mothers of twin boys had a significantly higher risk of endometrial cancer than women with singleton births only, whereas women with twin girls had an elevated risk before age 55 years. No significant association was seen with sex-noncordant twins, neither overall nor within age groups.