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.

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.

Is chronic low back pain a risk factor for diabetes? The Nord-Trøndelag Health Study.

OBJECTIVE: The purpose of this study was to examine the risk of diabetes associated with the presence or absence of chronic low back pain, considering both cross-sectional and cohort data. RESEARCH DESIGN AND METHODS: Analyses were based on the Norwegian HUNT2 and HUNT3 surveys of Nord-Trøndelag County. The prevalence of diabetes was compared in groups with and without chronic low back pain among 45 157 participants aged 30-69 years. Associations between low back pain at baseline and risk of diabetes were examined in an 11-year follow-up of 30 380 individuals with no baseline diagnosis of diabetes. The comorbidity between diabetes and low back pain was assessed at the end of follow-up. All analyses were carried out considering generalized linear models incorporating adjustment for other relevant risk factors. RESULTS: Cross-sectional analyses did not reveal any association between low back pain and diabetes. With adjustment for age, body mass index, physical activity and smoking, the cohort study of women showed a significant association between low back pain at baseline and risk of diabetes (RR 1.30; 95% CI 1.09 to 1.54, p=0.003). The association differed between age groups (p=0.015), with a stronger association in relatively young women. In men, no association was found in the whole age range (RR 1.02; 95% CI 0.86 to 1.21, p=0.82). No association was observed between diabetes and chronic low back pain at the end of follow-up. CONCLUSION: Among younger women, those with chronic low back pain may have an increased risk of diabetes.

Is there an association between vitamin D status and risk of chronic low back pain? A nested case-control analysis in the Nord-Trøndelag Health Study.

OBJECTIVES: To explore potential associations between vitamin D status and risk of chronic low back pain (LBP) in a Norwegian cohort, and to investigate whether relationships depend on the season of blood sample collection. DESIGN: A nested case-control study in a prospective data set. SETTING: The Norwegian community-based Nord-Trøndelag Health Study (HUNT). Data were collected in the HUNT2 (1995-1997) and HUNT3 (2006-2008) surveys. MAIN OUTCOME MEASURE: Chronic LBP, defined as LBP persisting at least 3 months continuously during the past year. PARTICIPANTS: Among individuals aged 19-55 years without LBP in HUNT2, a data set was generated including 1685 cases with LBP in HUNT3 and 3137 controls without LBP. METHODS: Blood samples from the participants collected in HUNT2 were analysed for serum 25-hydroxyvitamin D (25(OH)D) level. Associations with LBP in HUNT3 were evaluated by unconditional logistic regression analysis with adjustment for age, sex, work status, physical activity at work and in leisure time, education, smoking, and body mass index. RESULTS: No association between vitamin D status and risk of chronic LBP was found in the total data set (OR per 10 nmol/L 25(OH)D=1.01, 95% CI 0.97 to 1.06) or in individuals with blood samples collected in summer/autumn (OR per 10 nmol/L 25(OH)D=0.99, 95% CI 0.93 to 1.06). For blood samples drawn in winter/spring, associations differed significantly between women and men (p=0.004). Among women a positive association was seen (OR per 10 nmol/L 25(OH)D=1.11, 95% CI 1.02 to 1.20), but among men no significant association was observed (OR per 10 nmol/L 25(OH)D=0.90, 95% CI 0.81 to 1.01). CONCLUSIONS: Overall, no association between vitamin D status and risk of LBP was demonstrated. The association suggested in women for the winter/spring season cannot be regarded as established.

Data on gender contrasts in the risk of incident myocardial infarction by age. The Tromsø Study 1979-2012.

The data presented in this article relate to the research article entitled "Risk of incident myocardial infarction by gender: Interactions with serum lipids, blood pressure and smoking. The Tromsø Study 1979-2012" (Albrektsen et al., 2017) [1]. Data quantify the gender differences in the risk of myocardial infarction (MI) in terms of incidence rate ratios (IRR), in subgroups defined by serum lipids, blood pressure and smoking among persons aged 35-54 years, 55-74 years and 75-94 years, respectively. Data also describe the age- and gender-specific linear associations with the coronary heart disease (CHD) risk factors. IRRs for combined categories of age, gender and a CHD risk factor, with each category compared to the same reference group, are also shown. IRRs were calculated as estimates of relative risk in Poisson regression analyses of person-years at risk. Among 33,859 individuals at risk, a total of 622, 1308 and 816 were diagnosed with MI at ages 35-54, 55-74 and 75-94 years, respectively.

Risk of incident myocardial infarction by gender: Interactions with serum lipids, blood pressure and smoking. The Tromsø Study 1979-2012.

BACKGROUND AND AIMS: Overall, men have roughly twice the risk of myocardial infarction (MI) compared to women, but what causes this contrast is unclear. Identification of subgroups where the gender contrast in risk is particularly low or high, may provide new insight. In the search for such subgroups, we focus on gender-specific effects of established coronary heart disease (CHD) risk factors. Heterogeneity across age groups is also explored. METHODS: Population-based prospective study from Tromsø, Norway, comprising 33,859 individuals (51% women); 2746 individuals (854 women) received a diagnosis of MI during follow-up at ages 35-94 years. Incidence rate ratios (IRR) were calculated as estimates of relative risk in Poisson regression analyses. RESULTS: The association between total cholesterol and risk of MI was stronger for men than women, and IRR for men vs. women accordingly increased with increasing cholesterol, but the risk was higher for men in all subgroups (IRR in range 1.63-3.27), except among older people with low cholesterol levels. The adverse effect of increasing blood pressure (BP) was stronger for women, and IRR for gender diminished with increasing systolic (from 3.90 to 1.38) and diastolic BP (from 2.87 to 1.54). The gender contrast in risk was also substantially reduced in smokers ≥75 years. Associations with high-density lipoprotein cholesterol (HDL-C) did not differ between genders. CONCLUSIONS: Gender heterogeneity in associations with total cholesterol but not HDL-C indicates gender differences in associations with non-HDL-C. The stronger association with BP in women may relate to more severe hypertension-induced left ventricular hypertrophy.

Physical activity level at work and risk of chronic low back pain: A follow-up in the Nord-Trøndelag Health Study.

BACKGROUND: Physical activity in leisure time seems to reduce the risk of low back pain, but it is not known whether occupational activity, as recorded in a representative working population, produces a higher or lower risk. OBJECTIVE: To study associations between physical activity level at work and risk of chronic low back pain. METHODS: Associations were examined in a Norwegian prospective study using data from the HUNT2 and HUNT3 surveys carried out in the whole county of Nord-Trøndelag. Participants were 7580 women and 7335 men who supplied information about physical activity level at work. Levels considered were sedentary work, work involving walking but no heavy lifting, work involving walking and heavy lifting, and particularly strenuous physical work. Nobody in the cohort was affected by chronic low back pain at baseline. After 11 years, participants reported whether they suffered from chronic low back pain. Generalized linear modelling with adjustment for potential confounders was applied to assess associations with risk factors. RESULTS: In age-adjusted analyses both women and men showed statistically significant associations between physical activity at work and risk of chronic low back pain, suggesting positive relationships. For particularly strenuous physical work the relative risk of chronic low back pain was 1.30 (95% CI: 1.00-1.71) in women and 1.36 (95% CI 1.17-1.59) in men, compared to sedentary work. Women still showed a general association with activity level after adjustment for education, leisure time physical activity, BMI, smoking and occupational category. In men, the higher risk was only maintained for particularly strenuous work. CONCLUSION: In this cohort, women had a higher risk of chronic low back pain with work involving walking and heavy lifting or particularly strenuous work, compared to sedentary work. Men participating in particularly strenuous work also experienced a higher risk of chronic low back pain.

Lifelong Gender Gap in Risk of Incident Myocardial Infarction: The Tromsø Study.

Importance: It is not clear to what extent the higher incidence of coronary heart disease (CHD) in men vs women is explained by differences in risk factor levels because few studies have presented adjusted risk estimates for sex. Moreover, the increase in risk of CHD in postmenopausal women, possibly hormone related, may eventually eliminate the sex contrast in risk, but age-specific risk estimates are scarce. Objective: To quantify the difference in risk of incident myocardial infarction (MI) between men and women. Design, Setting and Participants: Population-based prospective study from Tromsø, Norway, comprising 33 997 individuals (51% women). Median follow-up time during ages 35 to 102 years was 17.6 years. Incidence rates (IRs) and incidence rate ratios (IRRs, relative risk) of MI were calculated in Poisson regression analysis of person-years at risk. The data analysis was performed in November 2015. Exposures: Sex, age, birth cohort, serum lipid levels, blood pressure, lifestyle factors, diabetes. Main Outcomes and Measures: Incident MI. Results: A total of 2793 individuals (886 women) received a diagnosis of MI during follow-up in the period 1979 through 2012. The IR increased with age in both sexes, with lower rates for women until age 95 years. Adjusted for age and birth cohort, the overall IRR for men vs women was 2.72 (95% CI, 2.50-2.96). Adjustment for high-density lipoprotein cholesterol and total cholesterol levels had the strongest impact on the risk estimate for sex, followed by diastolic blood pressure and smoking. However, the sex difference remained substantial even after adjustment for these factors (IRR, 2.07; 95% CI, 1.89-2.26). Men had higher risk throughout life, but the IRRs decreased with age (3.64 [95% CI, 2.85-4.65], 2.00 [95% CI, 1.76-2.28], and 1.66 [95% CI, 1.42-1.95] for age groups 35-54, 55-74, and 75-94 years, respectively). Adjustment for systolic blood pressure, diabetes, body mass index, and physical activity had no notable impact. Conclusions and Relevance: The observed sex contrast in risk of MI cannot be explained by differences in established CHD risk factors. The gender gap persisted throughout life but declined with age as a result of a more pronounced flattening of risk level changes in middle-aged men. The minor changes in IRs when moving from premenopausal to postmenopausal age in women make it unlikely that changes in female hormone levels influence the risk of MI.

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.

A Comparison of Anthropometric Measures for Assessing the Association between Body Size and Risk of Chronic Low Back Pain: The HUNT Study.

BACKGROUND: Previous work indicates that overweight and obese individuals carry an increased risk of experiencing chronic low back pain (LBP). It is not known, however, how the association with body size depends on the choice of anthropometric measure used. OBJECTIVE: This work compares relationships with LBP for several measures of body size. Different results may indicate underlying mechanisms for the association between body size and risk of LBP. METHODS: In a cohort study, baseline information was collected in the community-based HUNT2 (1995-1997) and HUNT3 (2006-2008) surveys in Norway. Participants were 10,059 women and 8725 men aged 30-69 years without LBP, and 3883 women and 2662 men with LBP at baseline. Associations with LBP at end of follow-up were assessed by generalized linear modeling, with adjustment for potential confounders. RESULTS: Relationships between waist-hip-ratio and occurrence of LBP at end of follow-up were weak and non-significant after adjustment for age, education, work status, physical activity, smoking, lipid levels and blood pressure. Positive associations with LBP at end of follow-up were all significant for body weight, BMI, waist circumference and hip circumference after similar adjustment, both in women without and with LBP at baseline, and in men without LBP at baseline. After additional mutual adjustment for anthropometric measures, the magnitude of the association with body weight increased in women without LBP at baseline (RR: 1.130 per standard deviation, 95% CI: 0.995-1.284) and in men (RR: 1.124, 95% CI 0.976-1.294), with other measures showing weak associations only. CONCLUSION: Central adiposity is unlikely to play a major role in the etiology of LBP. Total fat mass may be one common factor underlying the associations observed. The association with body weight remaining after mutual adjustment may reflect mechanical or structural components behind the relationship between overweight or obesity and LBP.

Association between body height and chronic low back pain: a follow-up in the Nord-Trøndelag Health Study.

OBJECTIVE: To study potential associations between body height and subsequent occurrence of chronic low back pain (LBP). DESIGN: Prospective cohort study. SETTING: The North-Trøndelag Health Study (HUNT). Data were obtained from a whole Norwegian county in the HUNT2 (1995-1997) and HUNT3 (2006-2008) surveys. PARTICIPANTS: Altogether, 3883 women and 2662 men with LBP, and 10,059 women and 8725 men without LBP, aged 30-69 years, were included at baseline and reported after 11 years whether they suffered from LBP. MAIN OUTCOME MEASURE: Chronic LBP, defined as pain persisting for 3 months during the previous year. RESULTS: Associations between body height and risk and recurrence of LBP were evaluated by generalised linear modelling. Potential confounders, such as BMI, age, education, employment, physical activity, smoking, blood pressure and lipid levels were adjusted for. In women with no LBP at baseline and body height ≥ 170 cm, a higher risk of LBP was demonstrated after adjustment for other risk factors (relative risk 1.19, 95% CI 1.03 to 1.37; compared with height <160 cm). No relationship was established among men or among women with LBP at baseline. CONCLUSIONS: In women without LBP, a body height ≥ 170 cm may predispose to chronic LBP 11 years later. This may reflect mechanical issues or indicate a hormonal influence.

Do abnormal serum lipid levels increase the risk of chronic low back pain? The Nord-Trøndelag Health Study.

BACKGROUND: Cross-sectional studies suggest associations between abnormal lipid levels and prevalence of low back pain (LBP), but it is not known if there is any causal relationship. OBJECTIVE: The objective was to determine, in a population-based prospective cohort study, whether there is any relation between levels of total cholesterol, high density lipoprotein (HDL) cholesterol and triglycerides and the probability of experiencing subsequent chronic (LBP), both among individuals with and without LBP at baseline. METHODS: Information was collected in the community-based HUNT 2 (1995-1997) and HUNT 3 (2006-2008) surveys of an entire Norwegian county. Participants were 10,151 women and 8731 men aged 30-69 years, not affected by chronic LBP at baseline, and 3902 women and 2666 men with LBP at baseline. Eleven years later the participants indicated whether they currently suffered from chronic LBP. RESULTS: Among women without LBP at baseline, HDL cholesterol levels were inversely associated and triglyceride levels positively associated with the risk of chronic LBP at end of follow-up in analyses adjusted for age only. Adjustment for the baseline factors education, work status, physical activity, smoking, blood pressure and in particular BMI largely removed these associations (RR: 0.96, 95% CI: 0.85-1.07 per mmol/l of HDL cholesterol; RR: 1.16, 95% CI: 0.94-1.42 per unit of lg(triglycerides)). Total cholesterol levels showed no associations. In women with LBP at baseline and men without LBP at baseline weaker relationships were observed. In men with LBP at baseline, an inverse association with HDL cholesterol remained after complete adjustment (RR: 0.83, 95% CI: 0.72-0.95 per mmol/l). CONCLUSION: Crude associations between lipid levels and risk of subsequent LBP in individuals without current LBP are mainly caused by confounding with body mass. However, an association with low HDL levels may still remain in men who are already affected and possibly experience a higher pain intensity.

Body mass index as a risk factor for developing chronic low back pain: a follow-up in the Nord-Trøndelag Health Study.

STUDY DESIGN: A population-based, prospective cohort study. OBJECTIVE: To determine whether overweight, obesity, or more generally an elevated body mass index (BMI) increase the probability of experiencing chronic low back pain (LBP) after an 11-year period, both among participants with and without LBP at baseline. SUMMARY OF BACKGROUND DATA: Chronic LBP is a common disabling disorder in modern society. Cross-sectional studies suggest an association between an elevated BMI and LBP, but it is not clear whether this is a causal relationship. METHODS: Data were obtained from the community-based HUNT 2 (1995-1997) and HUNT 3 (2006-2008) studies of an entire Norwegian county. Participants were 8733 men and 10,149 women, aged 30 to 69 years, who did not have chronic LBP at baseline, and 2669 men and 3899 women with LBP at baseline. After 11 years, both groups indicated whether they currently had chronic LBP, defined as pain persisting for at least 3 months continuously during the last year. RESULTS: A significant positive association was found between BMI and risk of LBP among persons without LBP at baseline. The odds ratio for BMI 30 or more versus BMI less than 25 was 1.34 (95% confidence interval [CI], 1.08-1.67) for men and 1.22 (95% CI, 1.03-1.46) for women, in analyses adjusted for age, education, work status, physical activity at work and in leisure time, smoking, blood pressure, and serum lipid levels. A significant positive association was also established between BMI and recurrence of LBP among women. LBP status at baseline had negligible influence on subsequent change in BMI. CONCLUSION: High values of BMI may predispose to chronic LBP 11 years later, both in individuals with and without LBP. The association between BMI and LBP is not explained by an effect of LBP on later change in BMI.

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.

The impact of body mass index on the prevalence of low back pain: the HUNT study.

STUDY DESIGN: A cross-sectional population-based study. OBJECTIVE: To examine the association between body mass index and chronic low back pain, with adjustment for potential confounders. SUMMARY OF BACKGROUND DATA: Although many studies have investigated this association, it is still unclear whether there is a general relationship between body mass index and low back pain which applies to all populations. METHODS: This study is based on data collected in the HUNT 2 study in the county of Nord-Trøndelag in Norway between 1995 and 1997. Among a total of 92,936 persons eligible for participation, 30,102 men and 33,866 women gave information on body mass index and indicated whether they suffered from chronic low back pain (69% participation rate). A total of 6293 men (20.9%) and 8923 women (26.3%) experienced chronic low back pain. Relations were assessed by logistic regression of low back pain with respect to body mass index and other variables. RESULTS: In both sexes, a high body mass index was significantly associated with an increased prevalence of low back pain. In men the estimated OR per 5 kg/m increase in body mass index was 1.07 (95% CI: 1.03-1.12) and in women 1.17 (95% CI: 1.14-1.21), after adjustment for age, with a significantly stronger association in women. Additional adjustment for education, smoking status, leisure time physical activity, employment status, and activity at work hardly affected these associations. No interactions were found with most other factors. CONCLUSION: This large population-based study indicates that obesity is associated with a high prevalence of low back pain. Further studies are needed to determine if the association is causal.

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.

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.

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.

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.