Stroke rates in non-anticoagulated individuals with and without atrial fibrillation and one non-sex CHA2DS2-VASc risk factor: a nationwide registry-based cohort (Atrial Fibrillation in Norway – AFNOR)

Background

Stroke prevention is fundamental in the management of atrial fibrillation (AF). However, in patients with intermediate risk of stroke (CHA2DS2-VASc score 2 in women; 1 in men) the net clinical benefit of oral anticoagulant (OAC) treatment is uncertain, as the treatment effect must be carefully balanced against the potential bleeding risk. Moreover, multiple risk factors included in the CHA2DS2-VASc score increase the risk of stroke independent of AF.

Purpose

We aimed to compare rates of ischemic and haemorrhagic stroke between non-anticoagulated individuals with and without AF in a nationwide cohort of individuals at intermediate risk of stroke.

Method

We identified a cohort of non-anticoagulated Norwegian individuals with and without non-valvular AF aged ≥18 years, with one non-sex CHA2DS2-VASc risk factor linking data from the Norwegian Population Registry, Patient Registry, Prescription Database and Cause of Death Registry. AF and comorbidities were identified with minimum three-year look-back period at study start and successively during follow up. Individuals without AF entered the study at date of first registered non-sex CHA2DS2-VASc risk factor while individuals with AF entered at the first date when both AF and first CHA2DS2-VASc risk factor were registered. Individuals with and without AF were followed from study start in 2011 until occurrence of stroke, death, emigration, OAC claim, increased CHA2DS2-VASc score or end of follow-up on December 31, 2018. Rates of ischemic and haemorrhagic stroke were calculated as the number of stroke cases per 100 person-years with 95% confidence intervals (CI).

Results

During 2011–2018, a total of 61,762 individuals with AF at intermediate risk of stroke and no previous OAC use were identified (mean age 63.2±7.6 years (SD); 37% women). In the AF population, a total of 1,304 ischemic strokes were registered during 109,881 person-years, and 127 haemorrhagic strokes during 109,559 person-years. In the corresponding intermediate risk non-AF population, 1,099,655 individuals (mean age 59.5±10.2 years (SD); 49.5% women) were identified, with a total of 6,081 ischemic strokes during 4,037,940 person-years and 3,037 haemorrhagic strokes during 4,022,952 person-years.

The rate of ischemic stroke was 1.19 (95% CI, 1.12–1.25) in AF-patients and 0.15 (95% CI, 0.15–0.15) in non-AF individuals per 100 person-years, corresponding to a rate difference of 1.04 excess stroke cases per 100 person-years in AF patients. The haemorrhagic stroke rate was 0.12 (95% CI, 0.10–0.14) in AF-patients and 0.08 (95% CI, 0.07–0.08) per 100 person-years in non-AF individuals. Similar rate differences were seen in both men and women.

Conclusion

In a nationwide population with one non-sex CHA2DS2-VASc risk factor and without OAC treatment, we found higher stroke rate in AF patients compared to the rest of the population without AF, with a stroke rate difference of ∼1% per year. Haemorrhagic stroke rates were generally low.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): South-Eastern Norway Regional Health Authority

Oral anticoagulation in atrial fibrillation patients at intermediate risk of stroke: a nationwide registry-based cohort (Atrial Fibrillation in Norway – AFNOR)

Background

The effect of oral anticoagulants (OAC) on prevention of stroke must be carefully balanced against the potential risk of bleeding in patients with atrial fibrillation (AF). The net benefit of OAC in AF patients at intermediate risk of stroke remains unclear.

Aim

We aimed to determine whether the rates of ischemic and haemorrhagic stroke differ between users and non-users of OAC in a nationwide cohort of AF patients at intermediate risk of stroke.

Method

We investigated the association between initiation of OAC treatment and rates of ischemic and haemorrhagic stroke in a cohort of Norwegian patients with non-valvular AF aged ≥18 years with one non-sex CHA2DS2-VASc risk factor registered from 2011 to 2018, linking data from the Norwegian Population Registry, Patient Registry, Prescription Database and Cause of Death Registry. Individuals using OAC at baseline were excluded. Each individual had at least a three years look-back period for identification of their first non-sex CHA2DS2-VASc risk factor, after which they entered the study cohort and were followed until occurrence of stroke, death, emigration, higher CHA2DS2-VASc score or end of follow-up on December 31, 2018. Individuals were defined as exposed to OAC from the first redeemed prescription of OAC with a reimbursement code for AF and throughout follow-up. Rates of ischemic and haemorrhagic stroke were calculated as the number of stroke cases per 100 person-years, with 95% confidence intervals (CI).

Results

During 2011–2018, a total of 61,631 individuals with AF and intermediate risk of stroke were included (mean age 63,8±7,6 years (SD); 37% women), of whom 75% initiated OAC treatment. In total, 1709 ischemic strokes (405 cases in OAC users and 1304 in non-users) were registered during 214,738 person-years, and 378 haemorrhagic strokes (251 cases in OAC users and 127 in non-users) during 213,487 person-years. The rate of ischemic stroke was 0.39 (95% CI, 0.35–0.43) and 1.19 (95% CI, 1.12–1.25) per 100 person-years in OAC users and non-users, respectively. The haemorrhagic stroke rate was 0.24 (95% CI, 0.21–0-27) and 0.12 (95% CI, 0.10–0.14) per 100 person-years in OAC users and non-users, respectively. Both ischemic and haemorrhagic stroke rates were highest among those over 65 years of age (Figure 1).

Conclusion

In a nationwide cohort of Norwegian AF patients at intermediate risk of stroke, three out of four initiated treatment with OAC. Use of OAC was associated with a considerably lower rate of ischemic stroke compared to non-OAC use. Although haemorrhagic stroke rates were increased in the OAC-users vs. non-users, the hemorrhagic stroke rates were generally low.

Funding Acknowledgement

Type of funding sources: Public hospital(s). Main funding source(s): Vestre Viken Health Trust Figure 1. Rates of ischemic and haemorrhagic stroke per 100 person-years in AF-patients at intermediate risk of stroke (CHA2DS2-VASc score 1 in men, score 2 in women) by OAC use during 2011 to 2018. Age corresponds to age at attainment of the first non-sex CHA2DS2-VASc risk factor.

Time trends in incidence rates of atrial fibrillation-related strokes in Norway 2001–2014: a nationwide analysis using data from the cardiovascular disease in Norway (CVDNOR) project

Background

Stroke incidence rates declined in Norway during 2001 to 2014. Atrial fibrillation (AF) incidence rates were stable in the same period.

Purpose

We aimed to study time trends in incidence (first time) of acute stroke hospitalizations and stroke deaths associated with AF in Norway in the period 2001–2014.

Methods

Nationwide hospital discharge diagnoses in the Cardiovascular Disease in Norway (CVDNOR) database and in the National Patient Registry were linked to the National Cause of Death Registry. All hospitalizations with acute stroke (including ischemic stroke, intracerebral bleeding and unspecified stroke) and out-of-hospital deaths with stroke as underlying cause in individuals 25 years and older were obtained during 1994–2014. Incident stroke was defined as the first hospitalization or out-of-hospital death due to stroke with no hospitalization for acute stroke or stroke sequela the past 7 years. Stroke was defined as AF-related if AF was registered during a hospitalization the past 7 years, or as underlying or contributing cause of death up to 28 days after the stroke hospitalization. Age-standardized incidence rates with 95% confidence intervals (CIs) were calculated using direct standardization to the age-distribution in the Norwegian population per 2001. Age-adjusted average yearly incidence rate ratios (IRR) with 95% CIs were estimated by negative binomial regression analyses.

Results

From 2001 to 2014 we identified 157 580 incident stroke cases of which 38 317 were AF-related. The proportion of incident strokes that were related to AF increased from 20.6% in 2001 to 26.3% in 2014. Age-standardized incidence rates of AF-related strokes per 100,000 person years were stable at 88 (85, 92) in 2001 and 79 (76, 83) in 2014, corresponding to a 0% average yearly change, IRR 1.00 (0.99, 1.00). The age-standardized incidence rates of non-AF-related strokes per 100,000 person years decreased from 334 (328, 341) in 2001 to 214 (209, 219) in 2014, corresponding to a 3% average yearly decrease, IRR 0.97 (0.97, 0.97).

Conclusion

The favourable trend in total stroke incidence rates from 2001 to 2014 does not include AF-related strokes. This may suggest that AF has become accountable for a higher proportion of incident strokes or that AF detection improved over this period.

Figure 1. Age-standardized incidence rates of stroke hospitalizations or out-of-hospital deaths per 100,000 person years (py) by year, illustrated as all strokes (blue horizontal line) and AF-related strokes (red horizontal line/height of red area). The height of the blue area illustrates the rate for non-AF related strokes.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Vestre Viken Hospital Trust (public hospital research fund)

P6563Time trends in incidence rates of atrial fibrillation in Norway 2004–2014. A CVDNOR project

Background

The reported incidence and prevalence of atrial fibrillation (AF) has been inconsistent among studies.

Purpose

We aimed to study time trends in incidence (first time) of AF hospitalizations or AF deaths in Norway in the period 2004–2014 by age and sex.

Methods

Nationwide hospital discharge diagnoses in the Cardiovascular Disease in Norway (CVDNOR) database and in the National Patient Registry were linked to the National Cause of Death Registry. All hospitalizations with AF as primary or secondary diagnosis and out-of-hospital deaths with AF as underlying cause (ICD-9: 427.3 or ICD 10: I48; AF or atrial flutter) in individuals ≥18 years were obtained during 1994–2014. Incident AF was defined as first hospitalization or out-of-hospital death due to AF with no previous hospitalization for AF the past 10 years. Age-standardized incidence rates with 95% confidence intervals (CIs) were calculated using direct standardization to the age-distribution in the Norwegian population per Jan 1st 2004. Age-adjusted average yearly incidence rate ratios (IRR) with 95% CIs were estimated by Poisson regression analyses. Accumulated prevalence during 1994–2014 was assessed in Norwegian residents 18 years and older per Dec 31st 2014.

Results

During 39,865,498 person years of follow up from 2004 to 2014 we identified 175,979 incident AF cases of which 30% were registered with AF as primary diagnosis, 69% as secondary diagnosis and 1% as out-of-hospital cause of death. The age-standardized incidence rate of AF hospitalization or out-of-hospital death per 100,000 person years was stable at 433 (426–440) in 2004 and 440 (433–447) in 2014. IRR were stable or declining across age groups of both sexes, except for the youngest age group 18–44 years, where incidence rates of AF hospitalization or out-of-hospital death increased by 2% per year, IRR 1.02 (1.01, 1.03). By 2014, the prevalence of AF assessed from hospital or death records was 2.9% in the adult population 18 years and older.

Conclusion

We found overall stable incidence rates of AF from 2004 to 2014 in the adult Norwegian population. Increased incidence rates of AF in the population 18–44 years are worrying and need further investigation.

Acknowledgement/Funding

The Norwegian Atrial Fibrillation Reseach Network

Sex-specific relevance of diabetes to occlusive vascular and other mortality: a collaborative meta-analysis of individual data from 980 793 adults from 68 prospective studies

BACKGROUND

Several studies have shown that diabetes confers a higher relative risk of vascular mortality among women than among men, but whether this increased relative risk in women exists across age groups and within defined levels of other risk factors is uncertain. We aimed to determine whether differences in established risk factors, such as blood pressure, BMI, smoking, and cholesterol, explain the higher relative risks of vascular mortality among women than among men.

METHODS

In our meta-analysis, we obtained individual participant-level data from studies included in the Prospective Studies Collaboration and the Asia Pacific Cohort Studies Collaboration that had obtained baseline information on age, sex, diabetes, total cholesterol, blood pressure, tobacco use, height, and weight. Data on causes of death were obtained from medical death certificates. We used Cox regression models to assess the relevance of diabetes (any type) to occlusive vascular mortality (ischaemic heart disease, ischaemic stroke, or other atherosclerotic deaths) by age, sex, and other major vascular risk factors, and to assess whether the associations of blood pressure, total cholesterol, and body-mass index (BMI) to occlusive vascular mortality are modified by diabetes.

RESULTS

Individual participant-level data were analysed from 980 793 adults. During 9·8 million person-years of follow-up, among participants aged between 35 and 89 years, 19 686 (25·6%) of 76 965 deaths were attributed to occlusive vascular disease. After controlling for major vascular risk factors, diabetes roughly doubled occlusive vascular mortality risk among men (death rate ratio [RR] 2·10, 95% CI 1·97-2·24) and tripled risk among women (3·00, 2·71-3·33; χ2 test for heterogeneity p<0·0001). For both sexes combined, the occlusive vascular death RRs were higher in younger individuals (aged 35-59 years: 2·60, 2·30-2·94) than in older individuals (aged 70-89 years: 2·01, 1·85-2·19; p=0·0001 for trend across age groups), and, across age groups, the death RRs were higher among women than among men. Therefore, women aged 35-59 years had the highest death RR across all age and sex groups (5·55, 4·15-7·44). However, since underlying confounder-adjusted occlusive vascular mortality rates at any age were higher in men than in women, the adjusted absolute excess occlusive vascular mortality associated with diabetes was similar for men and women. At ages 35-59 years, the excess absolute risk was 0·05% (95% CI 0·03-0·07) per year in women compared with 0·08% (0·05-0·10) per year in men; the corresponding excess at ages 70-89 years was 1·08% (0·84-1·32) per year in women and 0·91% (0·77-1·05) per year in men. Total cholesterol, blood pressure, and BMI each showed continuous log-linear associations with occlusive vascular mortality that were similar among individuals with and without diabetes across both sexes.

INTERPRETATION

Independent of other major vascular risk factors, diabetes substantially increased vascular risk in both men and women. Lifestyle changes to reduce smoking and obesity and use of cost-effective drugs that target major vascular risks (eg, statins and antihypertensive drugs) are important in both men and women with diabetes, but might not reduce the relative excess risk of occlusive vascular disease in women with diabetes, which remains unexplained.

FUNDING

UK Medical Research Council, British Heart Foundation, Cancer Research UK, European Union BIOMED programme, and National Institute on Aging (US National Institutes of Health).

Motor development in children prenatally exposed to selective serotonin reuptake inhibitors: a large population-based pregnancy cohort study

OBJECTIVES

To estimate the association between prenatal exposure to selective serotonin reuptake inhibitors (SSRIs) and motor development in children considering the effect of maternal symptoms of anxiety and depression before, during and after pregnancy.

DESIGN

Population-based prospective pregnancy cohort study.

SETTING

The Norwegian Mother and Child Cohort study (MoBa) (1999-2008).

POPULATION

A total of 51 404 singleton pregnancies.

METHODS

Self-reported use of SSRIs was collected for the 6 months before pregnancy and prospectively during pregnancy. We used ordinal logistic regression as the statistical analysis.

MAIN OUTCOME MEASURES

Motor development was assessed by maternal reports of fine and gross motor development at child age 3 years by items from the Ages and Stages Questionnaire (ASQ). The maternal ASQ scores were compared with data from a MoBa sub-study where clinicians assessed motor development with the Gross and Fine Motor Mullen scales of early learning.

RESULTS

In all 381 women (0.7%) reported use of SSRIs during pregnancy, of these 159 reported on at least two questionnaires (prolonged use). Prolonged SSRI exposure was associated with a delay in fine motor development, odds ratio 1.42 (95% CI 1.07-1.87) compared with no SSRI exposure, after adjusting for symptoms of anxiety and depression before and during pregnancy. Severity of maternal depression seemed to explain the association only partially. Stratifying on depression after pregnancy had no impact on the estimated effect of SSRIs.

CONCLUSIONS

Prolonged prenatal exposure to SSRIs was weakly associated with a delayed motor development at age 3 years, but not to the extent that the delay was of clinical importance.

TWEETABLE ABSTRACT

Long-term prenatal SSRI exposure is weakly associated with delayed motor development independent of depression.

Prenatal exposure to antidepressants and language competence at age three: results from a large population-based pregnancy cohort in Norway

OBJECTIVE

To examine the association between maternal use of selective serotonin reuptake inhibitors (SSRI) in pregnancy and language competence in their children at age three taking into account maternal symptoms of anxiety and depression.

DESIGN

Population-based prospective pregnancy cohort study.

SETTING

The Norwegian Mother and Child Cohort Study; recruited pregnant women from 1999 through 2008.

POPULATION

45,266 women with 51,748 singleton pregnancies.

METHODS

The association between short- or long-term use of SSRI during pregnancy and language competence in the child was investigated using multinomial logistic regression with three outcome categories: long, complicated sentences, fairly complete sentences and language delay.

MAIN OUTCOME MEASURES

Children's language competence at age three measured by maternal report on a validated language grammar scale.

RESULTS

Women reported use of SSRI in 386 (0.7%) pregnancies. Of these, 161 (42%) reported long-term use. Compared with children whose mothers took no SSRI, using the best language category as the reference, adjusted relative risk ratios (RRR) of having fairly complete sentences were 1.21 (95% CI 0.85-1.72) and 2.28 (1.54-3.38) for short- and long-term SSRI use, respectively. The adjusted RRRs of language delay were 0.86 (0.42-1.76) and 2.30 (1.21-4.37). Symptoms of anxiety and depression in pregnancy were independently related to language delay, adjusted RRR 1.25 (1.03-1.50) and 1.83 (1.40-2.40) for short- and long-term symptoms, respectively.

CONCLUSIONS

Prolonged use of SSRI during pregnancy was associated with lower language competence in children by age three independently of depression. Having symptoms of depression throughout pregnancy had an independent effect.

Metabolic risk factors and skin cancer in the Metabolic Syndrome and Cancer Project (Me-Can)

BACKGROUND

Little is known about the associations of metabolic aberrations with malignant melanoma (MM) and nonmelanoma skin cancer (NMSC).

OBJECTIVES

To assess the associations between metabolic factors (both individually and combined) and the risk of skin cancer in the large prospective Metabolic Syndrome and Cancer Project (Me-Can).

METHODS

During a mean follow-up of 12 years of the Me-Can cohort, 1728 (41% women) incident MM, 230 (23% women) fatal MM and 1145 (33% women) NMSC were identified. Most NMSC cases (76%) were squamous cell carcinoma (SCC) (873, 33% women). Hazard ratios (HRs) were estimated by Cox proportional hazards regression for quintiles and standardized z-scores (with a mean of 0 and SD of 1) of body mass index (BMI), blood pressure, glucose, cholesterol, triglycerides and for a combined metabolic syndrome score. Risk estimates were corrected for random error in the measurements.

RESULTS

Blood pressure per unit increase of z-score was associated with an increased risk of incident MM cases in men and women [HR 1·17, 95% confidence interval (CI) 1·04-1·31 and HR 1·18, 95% CI 1·03-1·36, respectively] and fatal MM cases among women (HR 2·39, 95% CI 1·58-3·64). In men, all quintiles for BMI above the reference were associated with a higher risk of incident MM. In women, SCC NMSC risk increased across quintiles for glucose levels (P-trend 0·02) and there was a trend with triglyceride concentration (P-trend 0·09).

CONCLUSION

These findings suggest that mechanisms linked to blood pressure may be involved in the pathogenesis of MM. SCC NMSC in women could be related to glucose and lipid metabolism.

Metabolic syndrome and rare gynecological cancers in the metabolic syndrome and cancer project (Me-Can)

BACKGROUND

Risk factors for rare gynecological cancers are largely unknown. Initial research has indicated that the metabolic syndrome (MetS) or individual components could play a role.

MATERIALS AND METHODS

The Metabolic syndrome and Cancer project cohort includes 288,834 women. During an average follow-up of 11 years, 82 vulvar, 26 vaginal and 43 other rare gynecological cancers were identified. Hazard ratios (HRs) were estimated fitting Cox proportional hazards regression models for tertiles and standardized z-scores [with a mean of 0 and a standard deviation (SD) of 1] of body mass index (BMI), blood pressure, glucose, cholesterol, triglycerides and MetS. Risk estimates were corrected for random error in the measurement of metabolic factors.

RESULTS

The MetS was associated with increased risk of vulvar [HR 1.78, 95% confidence interval (CI) 1.30-2.41) and vaginal cancer (HR 1.87, 95% CI 1.07-3.25). Among separate MetS components, 1 SD increase in BMI was associated with overall risk (HR 1.43, 95% CI 1.23-1.66), vulvar (HR 1.36, 95% CI 1.11-1.69) and vaginal cancer (HR 1.79, 95% CI 1.30-2.46). Blood glucose and triglyceride concentrations were associated with increased risk of vulvar cancer (HR 1.98, 95% CI 1.10-3.58 and HR 2.09, 95% CI 1.39-3.15, respectively).

CONCLUSION

The results from this first prospective study on rare gynecological cancers suggest that the MetS and its individual components may play a role in the development of these tumors.

Nonfasting triglycerides and risk of cardiovascular death in men and women from the Norwegian Counties Study

The association between nonfasting triglycerides and cardiovascular disease (CVD) has recently been actualized. The aim of the present study was to investigate nonfasting triglycerides as a predictor of CVD mortality in men and women. A total of 86,261 participants in the Norwegian Counties Study 1974–2007, initially aged 20–50 years and free of CVD were included. We estimated hazard ratios (HRs) for deaths from CVD, ischemic heart disease (IHD), stroke and all causes by level of nonfasting triglycerides. Mean follow-up was 27.0 years. A total of 9,528 men died (3,620 from CVD, 2,408 IHD, 543 stroke), and totally 5,267 women died (1,296 CVD, 626 IHD, 360 stroke). After adjustment for CVD risk factors other than HDL-cholesterol, the HRs (95% CI) per 1 mmol/l increase in nonfasting triglycerides were 1.16 (1.13–1.20), 1.20 (1.14–1.27), 1.26 (1.19–1.34) and 1.09 (0.96–1.23) for all cause mortality, CVD, IHD, and stroke mortality in women. Corresponding figures in men were 1.03 (1.01–1.04), 1.03 (1.00–1.05), 1.03 (1.00–1.06) and 0.99 (0.92–1.07). In a subsample where HDL-cholesterol was measured (n = 40,144), the association between CVD mortality and triglycerides observed in women disappeared after adjustment for HDL-cholesterol. In a model including the Framingham CHD risk score the effect of triglycerides disappeared in both men and women. In conclusion, nonfasting triglycerides were associated with increased risk of CVD death for both women and men. Adjustment for major cardiovascular risk factors, however, attenuated the effect. Nonfasting triglycerides added no predictive information on CVD mortality beyond the Framingham CHD risk score in men and women.

Metabolic Profile (Blood Pressure, Lipids and Body Mass Index) in Relation to Breast Cancer Mortality

Background: Metabolic profile (body mass, blood pressure, lipids) may affect biological mechanisms of importance for breast cancer. In the present study we have studied whether these factors are related to breast cancer mortality.Material and Methods: Within the Norwegian Counties Study, a population-based study (1974-2005), we identified 1364 female invasive breast cancer cases.Results: The 1364 cases had a mean age at diagnosis 57.5 years (range 27.1-79.4 years), mean body mass index (BMI) was 24.0 kg/m2, mean systolic blood pressure was 128.1 mmHg, mean diastolic blood pressure 78.6 mmHg, mean serum cholesterol was 6.17 mmol/L and mean HDL-cholesterol was 1.45 mmol/L. A total of 429 cases died during a mean follow-up of 8.2 years. Those with a BMI ≥30 kg/m2 had a 1.45 (CI, 1.07 to 1.95) higher risk of dying during the follow-up than women with a BMI of 18.5–25 kg/m2. Women in the highest tertile of blood pressure had a 43% increase in mortality compared to women in the lowest tertile of blood pressure (HR=1.43, 95% CI, 1.10 to 1.85). Additionally, women in the highest tertile of total cholesterol had a 29% increase in mortality compared to women in the lowest tertile (HR=1.29, 95% CI, 1.01 to 1.65).Conclusion: Our study supports a relationship between total mortality among breast cancer patients and metabolic profile.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3047.

Rose angina predicts 23-year coronary heart disease mortality in women and men aged 40-49 years

OBJECTIVE

To determine the long-term coronary heart disease (CHD) mortality in women and men with symptoms, according to the Rose Angina Questionnaire at a relatively young age.

DESIGN

Cohort study with the baseline survey conducted during 1974-8. Information on symptoms was collected by a short, three-item version of the Rose Angina Questionnaire. Participants were re-invited to a similar survey five years later and followed for mortality throughout 2000.

SETTING

Three counties in Norway (the Norwegian Counties Study).

PARTICIPANTS

16 616 men and 16 265 women aged 40-49 years and denying CHD in 1974-8.

MAIN OUTCOME MEASURE

CHD mortality during 23 years.

RESULTS

By the end of follow-up 1316 men (7.9%) and 310 women (1.9%) had died from CHD, including 16% (66/406) of men and 4% (24/563) of women with Rose angina in 1974-8. Rose angina implied an elevated mortality from CHD with adjusted hazard ratios 1.50 (95% CI 1.16 to 1.93) in men and 1.98 (95% CI 1.30 to 3.02) in women. According to calculations based on the Cox model these increases in risk are similar to those associated with elevations of total cholesterol by 1.8 mmol/l (men) and 2.5 mmol/l (women) or elevations of systolic blood pressure by 21 mm Hg (men) or 31 mm Hg (women).

CONCLUSIONS

Angina symptoms in ages as low as 40-49 years were associated with elevated long-term CHD mortality in Norwegian women and men. This indicates that the three-item version of the Rose Angina Questionnaire, although a screening tool rather than a diagnostic test, adds information on undiagnosed CHD in both sexes.

The Emerging Risk Factors Collaboration: analysis of individual data on lipid, inflammatory and other markers in over 1.1 million participants in 104 prospective studies of cardiovascular diseases

Many long-term prospective studies have reported on associations of cardiovascular diseases with circulating lipid markers and/or inflammatory markers. Studies have not, however, generally been designed to provide reliable estimates under different circumstances and to correct for within-person variability. The Emerging Risk Factors Collaboration has established a central database on over 1.1 million participants from 104 prospective population-based studies, in which subsets have information on lipid and inflammatory markers, other characteristics, as well as major cardiovascular morbidity and cause-specific mortality. Information on repeat measurements on relevant characteristics has been collected in approximately 340,000 participants to enable estimation of and correction for within-person variability. Re-analysis of individual data will yield up to approximately 69,000 incident fatal or nonfatal first ever major cardiovascular outcomes recorded during about 11.7 million person years at risk. The primary analyses will involve age-specific regression models in people without known baseline cardiovascular disease in relation to fatal or nonfatal first ever coronary heart disease outcomes. This initiative will characterize more precisely and in greater detail than has previously been possible the shape and strength of the age- and sex-specific associations of several lipid and inflammatory markers with incident coronary heart disease outcomes (and, secondarily, with other incident cardiovascular outcomes) under a wide range of circumstances. It will, therefore, help to determine to what extent such associations are independent from possible confounding factors and to what extent such markers (separately and in combination) provide incremental predictive value.

Long-term risk of tuberculosis among immigrants in Norway

BACKGROUND

Two-thirds of the tuberculosis (TB) cases in Norway were discovered among immigrants. Some cases were discovered at arrival, but many develop the disease several years post-migration. Knowledge about how long after migration to Norway TB were discovered will enable us to better target preventive measures including preventive therapy. This study examines the long-term risk of TB among immigrants in Norway.

METHODS

All non-Nordic immigrants who arrived in Norway between 1986 and 2002, as registered by the Norwegian Directorate of Immigration, were followed-up. Their TB status was determined from the National Tuberculosis Registry. Observation period for TB cases was calculated from the date of arrival in Norway to TB registration. For persons without TB, it was calculated from the date of arrival in Norway to the date of emigration from Norway, date of death, or until end of follow-up (December 31, 2002).

RESULTS

For immigrants from Africa and Asia, the TB rates were 190 and 80 per 100,000 person-years (PY), respectively, at 7 years post-migration. For immigrants from Somalia, Pakistan, Vietnam, and the former Yugoslavia, the rates were 520, 160, 210, and 40 per 100 000 PY respectively, at 7 years post-migration. These rates were 7 to 90 times higher than the crude TB incidence for Norway. This increased risk applies to both genders, pulmonary and extra-pulmonary sites.

CONCLUSION

These results indicate the need for health personnel to be aware that immigrants remain at high risk of TB many years post-migration. Screening for TB on arrival should be strengthened, and preventive therapy for those with recent TB infection should be considered.

Tuberculosis in Norway by country of birth, 1986-1999

OBJECTIVE

To estimate the standardised incidence ratio (SIR) of TB among the foreign-born in Norway.

METHOD

The expected number of TB cases was calculated by applying the sex- and age-specific incidence rates for those born in Norway to the corresponding foreign-born population. The SIR was measured as the ratio between observed and expected number of cases.

RESULTS

The expected number of TB cases was between zero and three for all selected countries; the observed number of cases was significantly higher. The SIR was highest for Africa (160, 95%CI 144-175) and lowest for USA/Canada (0.4, 95%CI 0.1-1.0). It was 883 for Somalia (95%CI 775-991), 122 for Vietnam (95%CI 106-139), 119 for Pakistan (95%CI 105-134), 115 for the Philippines (95%CI 91-144) and 49 for former Yugoslavia (95%CI 40-57). The SIR for all the foreign-born was 21 (95%CI 20-22), giving a population attributable risk of 38%. It was highest in the age group 15-39 years (95, 95%CI 89-101), and lowest for those 65 years and older (3, 95%CI 2.1-3.3). The SIR for extrapulmonary TB was also high in those aged 15-39 years (159, 95%CI 146-173).

CONCLUSION

SIRs for TB differ by country and continent of birth. Understanding local epidemiology and immigration patterns will help better target prevention efforts.

Cod liver oil consumption, smoking, and coronary heart disease mortality: three counties, Norway

It has been hypothesized that omega-3 fatty acid consumption may lessen the adverse effect of smoking on coronary heart disease (CHD) risk. Thus, we explored whether cod liver oil consumption was protective of coronary heart disease in a cohort of men and women participating in a cardiovascular disease screening in Norway. The study population was aged 35-54 at the time of the baseline screening conducted by the National Health Screening Service of Norway in 1977-1983. Of 56,718 age-eligible men and women, 52,138 participated, of whom 42,612 (82%) completed a dietary questionnaire. Cod liver oil use was reported by 12.5%. At baseline, cod liver oil users had lower triglycerides, adjusting for age, body mass index, time since last meal and income (p < or = .05). As of December 1992, 639 and 118 CHD deaths were observed among the men and women, respectively. Overall, we observed no effect of cod liver oil consumption reported at baseline and CHD mortality in Cox Proportional Hazards analyses [Hazard Ratio (HR) = 1.0 (0.8-1.3)]. In analyses, stratified by smoking status, never smokers and current smokers showed non-significant beneficial associations between cod liver oil use and CHD mortality (HR = 0.7, 95% CI = 0.4-1.5; and HR = 0.8, 95% CI = 0.6-1.2, respectively). However, among former smokers a non-significant excess risk of CHD mortality was associated with cod liver oil use (HR = 1.6, 95% CI = 0.9-2.6). Smokers, regardless of their cod liver oil use were at a substantially higher risk for CHD mortality relative to non-smokers. Omega-3 fatty acid supplementation, as practiced in this cohort, provided no significant benefits to CHD risk among study participants.

[Chronic low back pain in 40-year olds in 12 Norwegian counties]

In this study, a questionnaire and a short interview were used to estimate the prevalence of chronic low back pain alone and low back pain together with other musculo-skeletal pains among 40-year-old women and men in 12 Norwegian counties (a total of 67,338 persons). On average 2.4% of men and 1.7% of women had only chronic low back pain, while 5.7% of men and 9.2% of women in addition had other pains as well. Persons with low back pain only were approximately equally distributed across the counties. Greater variations across the counties and between the sexes were found in persons with additional pain. The duration of the pain did not vary significantly between the sexes or across the counties, but the duration was on average two years longer in cases of multi-cause pain. Reduced capacity for work because of pain was approximately equally distributed between the sexes and the groups. More women than men were unable to do their daily work. About one third in both groups (more men than women) had been absent from work because of pain during the last year. More women than men in both groups received national insurance benefits. Persons with only low back pains were approximately equally represented across all levels of education and regardless of marital status, while people with multi-cause pain were overrepresented among those with low levels of education and among the divorced.

Income, educational level and body height

The relation between adult body height and two socio-economic factors (income and educational level) was studied in a large, ethnically homogenous population. In the period 1980-1983 all persons aged 40-54 years (born 1926-1941) in two Norwegian counties were invited to a cardiovascular screening. Ninety per cent (or 38162 persons) of those invited attended and had their height measured. Information concerning income and education was available at an individual level from the 1980 national census. Strong, positive relations were found between mean body height and the socio-economic factors, relations that probably are due to conditions during growth influencing both height, attained education and income abilities. The difference between highest and lowest educational class was 3.3 cm in men and 3.2 cm in women, and between highest and lowest income group 3.5 cm in men and 4.2 cm in women. These differences could not be explained by the strong cohort effect of increasing height in the successive birth cohorts from 1926 to 1941 which also was evident. It should be emphasized that height only could explain a small fraction of the variance in the socio-economic factors and is thus not a usable indicator of an individual's socio-economic status. However, it might contribute with important information concerning social inequalities in groups or population.

Weight variability, weight change and the incidence of hip fracture: a prospective study of 39,000 middle-aged Norwegians

There is an increased risk of hip fracture and low bone mass in thin individuals. An association between weight loss and hip fracture has also been reported. In addition, it has been suggested that weight cycling might lead to bone loss. We studied weight variability and change in 19,938 women and 19,151 men who all attended three consecutive health examinations during an average period of 12 years, and assessed the effect of these on the incidence of hip fracture during a subsequent follow-up. Mean age at start of follow-up was 48.6 years in women and 48.5 years in men. For each subject weight variability and linear trend in weight change between the three examinations were assessed by linear regression of weight versus time. The cohort was followed on average 11.6 years from the third examination with respect to hip fracture. During follow-up, 148 hip fractures were identified in women and 59 in men. In both sexes, those with most weight variability had increased risk of fracture (relative risk (RR) = 2.07, 95% confidence interval (CI) 1.24-3.46 in women, and RR = 2.70, 95% CI 1.25-5.86 in men, high vs low quarter of weight variability). Overall, the effect of weight variability was not affected by adjustment for body mass index and linear trend in weight change. In men, there was also an association between weight loss and hip fracture. In summary, high weight variability defined a group with increased risk of hip fracture in this middle-aged cohort. The effect was independent of body mass index and linear trend in weight change. Whether weight variability leads to increased risk of fracture per se or whether it defines a group with otherwise increased risk of fracture is not known, and needs further investigation.

Body mass index and cardiovascular mortality at different levels of blood pressure: a prospective study of Norwegian men and women

STUDY OBJECTIVE

The study investigated the joint effect of body mass index and systolic blood pressure on cardiovascular and total mortality.

DESIGN

This was a prospective cohort study. The main outcome measures were age adjusted mortality and relative risks estimated from survival models.

SETTING

The population of the city of Bergen, Norway.

PARTICIPANTS

Subjects were 21,145 men and 30,330 women aged 30-79 years at the time of examination in 1963.

MAIN RESULTS

Both cause specific and all cause mortality increased with systolic blood pressure within each category of body mass index. Stroke mortality was not significantly associated with body mass index when adjusted for systolic blood pressure in either age group of men or women. Coronary heart disease mortality increased on average 30% per 5 kg/m2 increase in body mass index in men and women aged 30-59 years at baseline. Adjusted for systolic blood pressure, the relative risks were reduced to 1.20 (95% confidence interval (CI) 1.12, 1.29) in men and 1.10 (95% CI 1.03, 1.18) in women. They were similar at each level of systolic blood pressure. For coronary heart disease mortality in men and women aged 60-79 years at measurement a negative interaction between body mass index and systolic blood pressure was suggested in the first five years. Excluding the first five years, adjusted relative risks per 5 kg/m2, were 1.05 (95% CI 0.96, 1.15) in men and 1.11 (95% CI 1.04, 1.17) in women in the older age group. There was an upturn in cardiovascular mortality at low levels of body mass index in both age groups of women, but not in men.

CONCLUSIONS

Hypertension is an important risk factor for cardiovascular and all cause mortality even in the obese. Body mass index is generally a weak predictor of cardiovascular mortality in this population. It is a stronger risk factor of coronary death in men when measured at a younger age. Thin people with hypertension are not at particularly high risk of death from coronary heart disease compared with their obese counterparts, except possibly in the first few years after measurement in the elderly. Being underweight is associated with increased risk of death from all cardiovascular causes in women, but not in men.

Mortality from stroke, coronary heart disease and all causes related to blood pressure and length of follow-up

Measurements of blood pressure in 52,064 men and women in the city of Bergen, Norway, who were 30 to 89 years in 1963, have been related to mortality occurring in different intervals of the follow-up period from 1963 throughout 1983. Blood pressure measurements obtained on one occasion were highly predictive of both coronary heart disease, stroke and all-cause mortality several years after measurements. The relative risk of stroke mortality associated with blood pressure varied little in the first ten to fifteen years, but the predictive power was clearly lower in the last five years of follow-up. The relative risk of death from coronary heart disease was stable in the whole period of follow-up. The risk curves relating coronary heart disease mortality to diastolic blood pressure in men and women aged 60-79 years at screening had the same shape in the first five years as in the rest of the follow-up. No J-shaped association was seen in either time interval.

Blood pressure and twenty-year mortality in the city of Bergen, Norway

A blood pressure survey was carried out in 1963 in the city of Bergen, Norway. The relation between 20-year mortality and blood pressure in 52,064 participants aged 30-89 years at examination was analyzed. Increased blood pressure was related to increased mortality from coronary heart disease, stroke, and all causes in all age groups except the oldest, where a more irregular pattern was present. The relative risks decreased with age at screening, while the absolute increase in mortality with increasing blood pressure was greatest in persons aged 60-69 or 70-79 years at screening. A log-linear relation between systolic blood pressure and coronary heart disease and stroke mortality was seen in both men and women. An upturn in total mortality at low systolic blood pressures was suggested in the groups aged 60 years or more at screening. An upturn, or leveling off, was also seen at low diastolic blood pressures for total deaths and stroke deaths in both men and women.

A comparison of Poisson regression models fitted to multiway summary tables and Cox's survival model using data from a blood pressure screening in the city of Bergen, Norway

Multiplicative models for the association between blood pressure and coronary heart disease mortality in 5201 men aged 40-49 years at time of examination were compared. Piecewise exponential models fitted to summary tables formed by cross-classification by three systolic and three diastolic blood pressure groups, two age groups and three time intervals gave results close to the Cox model for continuous data. The parametric integrated baseline hazard functions estimated from grouped data were close to Breslow's nonparametric estimate in the Cox model.

Reliability of the Reflotron in the determination of cholesterol

Measurements of total cholesterol in the field by means of the Reflotron dry-chemistry system (capillary blood) were compared to total cholesterol obtained by a standardized conventional wet-chemistry method in a clinico-chemical laboratory (serum). A total of 1200 people participated in the study. Two identical Reflotron machines were used. In the first period of the study an excellent agreement was found between Reflotron measurements of a reference serum provided by the manufacturer (mean, 4.99 mmol/l; CV, 1.8%) and the stated value (4.97 mmol/l). In the rest of the study higher values and greater variation were found with the Reflotron (mean, 5.32 mmol/l; CV 5.2%). Clearly the Reflotron measurements in the latter period of study were not reliable. In the period with stable instruments most of the values obtained at the two Reflotron machines differed from each other by less than 10%, with a mean difference of 0.08 mmol/l. Reflotron (both machines) and wet-chemistry measurements agreed well for the first 500 participants in the study (mean difference, Reflotron-wet-chemistry, -0.008 mmol/l; 95% confidence interval, -0.035 to 0.019 mmol/l; correlation, 0.967). In this period most Reflotron values differed from wet-chemistry values by less than 9% below to 9% above. With the next 200 participants the Reflotron gave on average slightly higher values than wet-chemistry measurements. The coefficients of variation for measurement variation were higher for Reflotron that for wet-chemistry even in the period with stable instruments. In all parts of the study period a lower HDL-cholesterol level was associated with larger differences between total cholesterol determined by Reflotron and wet-chemistry.

Coffee, dietary habits, and serum cholesterol among men and women 35-49 years of age

The relations between coffee and dietary habits and between coffee, dietary habits, and serum cholesterol were examined in 11,912 men and 12.328 women aged 35-49 years in the Cardiovascular Disease Risk Factor Study in Oppland, southern Norway, 1976-1978. Dietary data are based on results from a self-administered questionnaire. In both sexes, the dietary pattern of persons with a high coffee consumption differed from that of persons with a low coffee consumption: Heavy coffee drinkers had a higher consumption of bread, potatoes, and butter or margarine per slice of bread and more frequent use of hard margarine; men had a higher consumption of eggs and a lower consumption of skim milk. These results suggest a higher total food and fat consumption and a lower ratio of polyunsaturated to saturated fatty acids among heavy coffee drinkers. However, only 20% of the variation in coffee consumption was explained by dietary and lifestyle variables. The study confirmed a positive relation between serum cholesterol and use of butter or hard margarine (p less than 0.001) and between serum cholesterol and coffee consumption (p less than 0.001). Bread consumption and milk consumption were negatively correlated to serum cholesterol. The negative association with skim milk was significant only in women (p less than 0.01).

The negligible influence of premarital cohabitation on marital fertility in current Danish cohorts, 1975

This paper studies the influence of premarital cohabitation on marital fertility by applying life table methods to data for cohorts of Danish women born in 1926-1955, collected in retrospective interviews made in 1975. For each five-year cohort, the data have been analyzed by duration of marriage or by duration since previous birth, for women who had no reported births before marriage. Our main empirical results are: (a) that women who married at age 15-19 had higher rates of marital first and second births than those married at ages 20-24, and (b) that premarital cohabitation had very little influence on births of these two first orders in our data.