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

Vascular risk factor control and adherence to secondary preventive medication after ischaemic stroke

BACKGROUND

Studies regarding adequacy of secondary stroke prevention are limited. We report medication adherence, risk factor control and factors influencing vascular risk profile following ischaemic stroke.

METHODS

A total of 664 home-dwelling participants in the Norwegian Cognitive Impairment After Stroke study, a multicenter observational study, were evaluated 3 and 18 months poststroke. We assessed medication adherence by self-reporting (4-item Morisky Medication Adherence Scale) and medication persistence (defined as continuation of medication(s) prescribed at discharge), achievement of guideline-defined targets of blood pressure (BP) (<140/90 mmHg), low-density lipoprotein cholesterol (LDL-C) (<2.0 mmol L^-1 ) and haemoglobin A1c (HbA1c) (≤53 mmol mol^-1 ) and determinants of risk factor control.

RESULTS

At discharge, 97% were prescribed antithrombotics, 88% lipid-lowering drugs, 68% antihypertensives and 12% antidiabetic drugs. Persistence of users declined to 99%, 88%, 93% and 95%, respectively, at 18 months. After 3 and 18 months, 80% and 73% reported high adherence. After 3 and 18 months, 40.7% and 47.0% gained BP control, 48.4% and 44.6% achieved LDL-C control, and 69.2% and 69.5% of diabetic patients achieved HbA1c control. Advanced age was associated with increased LDL-C control (OR 1.03, 95% CI 1.01 to 1.06) and reduced BP control (OR 0.98, 0.96 to 0.99). Women had poorer LDL-C control (OR 0.60, 0.37 to 0.98). Polypharmacy was associated with increased LDL-C control (OR 1.29, 1.18 to 1.41) and reduced HbA1c control (OR 0.76, 0.60 to 0.98).

CONCLUSION

Risk factor control is suboptimal despite high medication persistence and adherence. Improved understanding of this complex clinical setting is needed for optimization of secondary preventive strategies.

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

Blood pressure, smoking and body mass in relation to mortality from stroke and coronary heart disease in the elderly. A 10-year follow-up in Norway

OBJECTIVES

To examine the association between blood pressure, smoking and body mass index (BMI) and cerebro- and cardiovascular mortality in a population of healthy elderly.

DESIGN

Ten-year mortality follow-up of elderly men and women who participated in the Nord-Trøndelag Health Study 1984-86.

SETTING

Nord-Trøndelag county, Norway.

SUBJECTS

3121 men and 3271 women aged 70 years and older, free from any diagnosed atherosclerotic diseases or diabetes at baseline.

MAIN OUTCOME MEASURES

Relative risk of cerebro- and cardiovascular mortality and all-cause mortality according to blood pressure, smoking and BMI.

RESULTS

There was a consistent, positive association between systolic and diastolic blood pressure and cerebro- and cardiovascular mortality. The association persisted after adjustment for potential confounding factors, and was strongest for cerebrovascular mortality; the adjusted relative risks for systolic blood pressure categories 160-179 mmHg and > or = 180 mmHg in men were 1.63 (95% confidence interval, CI 1.06-2.53) and 2.19 (95% CI 1.39-3.44) compared to blood pressure < 140 mmHg. In women, the corresponding relative risks were 1.54 (95% CI 0.93-2.56) and 2.12 (95% CI 1.29-3.50). For diastolic blood pressure the adjusted relative risks in categories 100-109 and > or = 110 mmHg in men were 1.88 (95% CI 1.19-2.95) and 3.06 (95% CI 1.79-5.21) compared to pressure <90 mmHg. The corresponding relative risks in women were 1.75 (95% CI 1.05-2.91) and 2.02 (95% CI 1.04-3.93). Current smoking increased cardiovascular mortality in both men and women, and among women, BMI was negatively associated with all-cause mortality.

CONCLUSIONS

These findings add to the growing evidence that hypertension is a major risk factor for mortality from stroke and coronary heart disease among the elderly and the very old.

[Pharmacological prevention of cardiovascular diseases in general practice]

BACKGROUND

In this paper the Norwegian College of General Practitioners, Working Group on Hypertension report recommendations for primary preventive drug treatment of elevated cardiovascular risk.

MATERIAL AND METHODS

Updated metaanalyses and randomised controlled trials are the main basis for the recommendations. The purpose of treating hypertension is prevention of cardiovascular diseases. Drug treatment with documented effect on morbidity and mortality is therefore recommended. We have also evaluated the cost effectiveness of drug treatment.

RESULTS

An estimate of the total risk of future cardiovascular disease is a necessary basis for treatment decisions. This paper presents tools for estimating total cardiovascular risk. Drug treatment is recommended if ten-year risk exceeds 20% or blood pressure equals or exceeds 170/100 mmHg. Drug treatments include antihypertensive, antithrombotic, antidiabetic and lipid-lowering drugs with documented effect on hard endpoints. Aspirin, thiazides, betablockers, metformin, calcium blockers, ACE inhibitors and statins are all drugs with documented effects on significant endpoints, but the costs of these treatments differ substantially.

INTERPRETATION

Drug treatment to prevent cardiovascular disease should be recommended for patients at significant risk of cardiovascular disease. Drugs with documented effect on morbidity and mortality should be used. Considerations of costs are important in treatment decisions.

[Life style advice provided by primary health care to prevent cardiovascular diseases]

BACKGROUND

The Working Group on Hypertension of the Norwegian College of General Practitioners reports in this paper on the documentation on behavioural advice in the prevention of cardiovascular disease. Emphasis is given to hypertension.

MATERIAL AND METHODS

The recommendations are mainly based on updated metaanalyses and randomised controlled trials. Hypertension is treated to prevent cardiovascular disease; that is why we put emphasis on documentation with significant end points. The validity of the documentation for general practice is assessed. We have also assessed whether certain methods or theories for behavioural change could be helpful to the general practitioner.

RESULTS

The value of advice against smoking, dietary advice (increased intake of grain products, vegetables, fruit, poultry and fish), and advice about exercise are well documented and applicable in general practice. Respect for the patient's autonomy and interest in the patients and their health-related habits seem to be important factors for improving doctor's chances of influencing patient behaviour.

INTERPRETATION

The value of life-style advice is well documented and should play an important role in clinical strategies to prevent cardiovascular disease in high-risk patients.

Physical activity and stroke mortality in women. Ten-year follow-up of the Nord-Trondelag health survey, 1984-1986

BACKGROUND AND PURPOSE

Few studies have reported a protective effect of physical activity on stroke in women, particularly among elderly women. This study was conducted to examine the association between different levels of leisure-time physical activity and stroke mortality in a large prospective study of middle-aged and elderly women.

METHODS

We conducted a 10-year mortality follow-up of women aged >/=50 years, free from stroke at baseline (n=14 101), who participated in the Nord-Trondelag Health Survey in Norway during 1984-1986. Main outcome measures were relative risk of stroke mortality according to increasing levels of physical activity, with the least active group used as reference.

RESULTS

In groups aged 50 to 69, 70 to 79, and 80 to 101 years, the relative risk of dying decreased with increasing physical activity, after adjustment for potentially confounding factors. In groups aged 50 to 69 and 70 to 79 years, the most active women had an adjusted relative risk of 0. 42 (95% CI, 0.24 to 0.75) and 0.56 (95% CI, 0.36 to 0.88), respectively. In the group aged 80 to 101 years, there was a consistent negative association with physical activity; the adjusted relative risk for the most active was 0.57 (95% CI, 0.30 to 1.09).

CONCLUSIONS

Physical activity was associated with reduced risk of death from stroke in middle-aged and elderly women. This association persisted after we excluded individuals with prevalent cardiovascular and cerebrovascular disease at baseline and women who died during the first 2 years of follow-up. These observations strengthen the evidence that physical activity should be part of a primary prevention strategy against stroke in women.

Identification of incident stroke in Norway: hospital discharge data compared with a population-based stroke register

BACKGROUND AND PURPOSE

The validity of hospital discharge diagnoses is essential in improving stroke surveillance and estimating healthcare costs of stroke. The aim of this study was to assess sensitivity, positive predictive value, and accuracy of discharge diagnoses compared with a stroke register.

METHODS

A record linkage was made between a population-based stroke register and the discharge records of the hospital serving the population of the stroke register (n=70 000). The stroke register (including patients aged 15 and older and with no upper age limit), applied here as a "gold standard," was used to estimate sensitivity, positive predictive value, and accuracy of the discharge diagnoses classification. The length of stay in hospital by stroke patients was measured.

RESULTS

Identifying cerebrovascular diseases by hospital discharge diagnoses (International Classification of Diseases, 9th Revision [ICD-9], codes 430 to 438.9, first admission) lead to a substantial overestimation of stroke in the target population. Restricting the retrieval to acute stroke diagnoses (ICD-9 codes 430, 431, 434, and 436) gave an incidence estimate closer to the "true" incidence rate in the stroke register. Selecting ICD-9 codes 430 to 438 of cerebrovascular diseases gave the highest sensitivity (86%). The highest positive predictive value (68%) was achieved by selecting acute stroke diagnoses (ICD-9 codes 430, 431, 434, and 436), at the expense of a lower sensitivity (81%). Accuracy of ICD codes 430 to 438.9 (n=678) revealed the highest proportion of incident strokes identified by the acute stroke diagnoses (ICD-9 codes 430, 431, 434, and 436). Seventy-four percent of hospital discharge diagnoses classified as first-ever stroke kept the original diagnosis. Only 4.6% of the discharge diagnoses were classified as nonstroke diagnoses after validation. The estimation of length of stay in the hospital was improved by selection of acute stroke diagnoses from hospital discharge data (ICD-9 codes 430, 431, 434, and 436), which gave the same estimate of length of stay, a median of 8 days (2.5 percentile=0 and 97.5 percentile=56), compared with a median of 8 days (2.5 percentile=0 and 97.5 percentile=51) based on the stroke register.

CONCLUSIONS

Hospital discharge data may overestimate stroke incidence and underestimate the length of stay in the hospital, unless selection routines of hospital discharge diagnoses are restricted to acute stroke diagnoses (ICD-9 codes 430, 431, 434, and 436). If supplemented by a validation procedure, including estimates of sensitivity, positive predictive value, and accuracy, hospital discharge data may provide valid information on hospital-based stroke incidence and lead to better allocation of health resources. Distinguishing subtypes of stroke from hospital discharge diagnoses should not be performed unless coding practices are improved.

Epidemiology of stroke in Innherred, Norway, 1994 to 1996. Incidence and 30-day case-fatality rate

BACKGROUND AND PURPOSE

In Norway, as well as other industrialized countries, mortality from stroke has declined over the past decades. Data on stroke morbidity are lacking. This study was conducted to determine the incidence, case fatality, and risk factors of stroke in a defined Norwegian population.

METHODS

During the period 1994 to 1996, a population-based stroke registry collected uniform information about all cases of first-ever and recurrent stroke occurring in people aged > or = 15 years in the region of Innherred in the central part of Norway (target population 70,000), where the prevalence of cardiovascular risk factors was screened in 1984 to 1986 and 1995 to 1997.

RESULTS

During the 2 years of registration (September 1, 1994, to August 31, 1996), 432 first-ever (72.8%) and 161 recurrent (27.2%) strokes were registered. The crude annual incidence rate was 3.12/1000 (2.85/1000 for males and 3.38/1000 for females). Adjusted to the European population, the annual incidence rate of first-ever stroke was 2.21/1000. The annual incidence rate of cerebral infarction was 2.32/1000, intracerebral hemorrhage 0.32/1000, subarachnoid hemorrhage 0.19/1000, and unspecified stroke 0.38/1000. The 30-day case-fatality rate was 10.9% for cerebral infarction, 37.8% for intracerebral hemorrhage, and 50.0% for unspecified stroke. Fourteen percent of the patients were found outside the hospital, and only 50% of the suspected stroke cases in the hospital (at admission or reviewed discharge diagnosis of ICD-9 codes 430 to 438) fitted the final inclusion criteria.

CONCLUSIONS

This first population-based stroke register in Norway revealed incidence rates of stroke similar to other Scandinavian countries, and comparison between other European countries did not indicate regional variations within Western Europe.

[What do we know about the frequency of stroke? A review of incidence studies]

In Norway, mortality from stroke has declined during the last 30-40 years. It is unknown whether the frequency of stroke has declined. This article presents studies on incidence and trends in incidence of stroke in different countries, especially Scandinavian countries. Geographical differences in incidence are small, when the rates are compared, adjusted for age and sex. Time trend studies on incidence give conflicting results. Some studies suggest increasing incidence of stroke, others a decrease or even no change of incidence. The age-standardised incidence rate (adjusted to the Norwegian population) from six studies in people aged 55-84 years is estimated to 6-8 per 1,000 per year. Little is known about incidence and time trend in Norway. Factors of importance for primary prevention of stroke (e.g. treatment of hypertension), treatment and rehabilitation of the stroke patient and knowledge about the incidence.

Vesicular stomatitis virus infection enhances invasiveness of Salmonella typhimurium

When mouse fibroblast L-929 cells were pre-infected with vesicular stomatitis virus, an enhancement of invasiveness by Salmonella typhimurium was observed. The effect was more pronounced when higher virus doses were used. Short-time (5 h) pre-incubation with virus caused a moderate enhancement of invasiveness. When virus pre-incubation time was increased to 8 h or 13 h, a further enhancement was observed. Results obtained after pre-incubation with UV inactivated virus were similar to that achieved by the short-time pre-incubation with the corresponding viable virus preparation. This indicates (i) an early phase of virus infection, when virus causes enhancement of invasiveness that is not dependent on viral nucleic acid induced metabolism, and (ii) a later phase, when virus-induced metabolism is necessary for the enhancement. When virus and bacteria were given concomitantly to infant mice, lethality was increased compared to groups that only received virus or bacteria. The data indicate that vesicular stomatitis virus aggravates infection with a facultatively intracellular bacterium, partly by enhancing the invasiveness of the bacteria.