Tom Skyhøj Olsen

Danish Cancer Society, København, Capital Region, Denmark

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Publications (135)

  • Source
    Vanna Albieri · Tom Skyhøj Olsen · Klaus Kaae Andersen
    [Show abstract] [Hide abstract] ABSTRACT: Background Identifying migraineurs by triptan utilization we studied risk for stroke in migraineurs compared to the general population. Methods A cohort study including all citizens 25–80 years of age in Denmark 2003–2011 was conducted. All persons prescribed triptans, and all those hospitalized for a first stroke were identified in the Danish Registries. Information on stroke severity/subtype and cardiovascular risk factors was available for stroke patients. Findings Of the 49,711 patients hospitalized for a first stroke, 1084 were migraineurs using triptans. Adjusting for age, sex, income, and educational level, risk for stroke was higher among migraineurs in respect to all strokes (RR 1.07; CI 1.01–1.14) and ischemic strokes (RR 1.07; CI 1.00–1.14). Risk for hemorrhagic stroke was increased but only in women (RR 1.41; CI 1.11–1.79). Risk was for mild strokes (RR 1.31; CI 1.16–1.48) while risk for severe strokes was lower among migraineurs (RR 0.77; CI 0.65–0.91). Risk was age-related; highest among women 25–45 years (RR ≈ 1.7). Risk was unrelated to numbers of dispensations. Interpretation Migraineurs identified by triptan utilization had higher risk for stroke. Strokes were minor and cardiovascular risk factors were less prevalent pointing to a migraine-specific etiology of stroke different from that of thromboembolism.
    Full-text available · Article · Feb 2016 · EBioMedicine
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    Christian Dehlendorff · Klaus Kaae Andersen · Tom Skyhøj Olsen
    [Show abstract] [Hide abstract] ABSTRACT: Uncertainty remains about whether stroke affects men and women similarly. We studied differences between men and women with regard to stroke severity and survival. We used the Danish Stroke Registry, with information on all hospital admissions for stroke in Denmark between 2003 and 2012 (N=79 617), and the Danish Register of Causes of Death. Information was available on age, sex, marital status, stroke severity, stroke subtype, socioeconomic status, and cardiovascular risk profile. We studied only deaths due to the index stroke, with the assumption that death reported on death certificates as due to stroke was related to the index stroke if death occurred within the first week or month after stroke. Multivariate Cox regression analysis and multiple imputation were applied. Stroke was the cause of death for 4373 and 5512 of the 79 617 patients within 1 week (5.5%) or 1 month (6.9%), respectively. After the age of 60 years, women had more severe strokes than men. Up to ages in the mid-60s, no difference in the risk of death from stroke was seen between the 2 sexes. For people aged >65 years, however, the risk gradually became greater in men than in women and significantly so (>15%) from the mid-70s (adjusted for age, marital status, stroke severity, stroke subtype, socioeconomic status, and cardiovascular risk factors). Results were essentially the same when analyzing deaths within 1 week, 1 month and ischemic and hemorrhagic stroke separately. Stroke affects women and men differently. Elderly women were affected more severely than elderly men but were more likely to survive. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.
    Full-text available · Article · Jul 2015 · Journal of the American Heart Association
  • C. Dehlendorff · T. Olsen · K. K. Andersen
    Article · Apr 2015 · International Journal of Stroke
  • T. Olsen · C. Dehlendorff · K. K. Andersen
    Article · Apr 2015 · International Journal of Stroke
  • Christian Dehlendorff · Klaus K Andersen · Tom S Olsen
    Article · Jan 2015 · JAMA Neurology
  • Christian Dehlendorff · Klaus K. Andersen · Tom S. Olsen
    Article · Jan 2015
  • [Show abstract] [Hide abstract] ABSTRACT: Background and purpose: The risk for stroke is higher in low-income groups. It is not clear whether these groups also have a higher risk for death after a stroke. Methods: We studied survival in relation to income and level of education in all patients aged >40 years admitted to hospital for stroke in Denmark in 2003 to 2012. All Danish hospitals report data to the Danish Stroke Register for all patients admitted for acute stroke, including age, sex, stroke severity, subtype, and a cardiovascular risk profile. Information on income and education was obtained from Statistics Denmark; deaths from all causes from the Civil Registration Registry. Results: Information on education and disposable income was available for 56 581 Danes hospitalized for stroke during the 9.5-year study period. Median length of follow-up was 3.1 years. For the entire follow-up period, there was a significant, stepwise, independent relation between income and risk for death after stroke, which was 30% higher for the lowest than for the highest quintile income group (relative risk, 0.70, 95% confidence interval, 0.65-0.74). People aged <65 years with basic education had a slightly higher risk for death than those with the longest (relative risk, 1.15; 95% confidence interval, 1.02-1.30). Death within 1 month was not associated with income or education. Conclusions: The survival of patients with low income was reduced by 30% as compared with those with high income. Education had only a modest effect and only in patients aged <65 years. The impact of socioeconomic position was on late but not on early poststroke death.
    Article · Oct 2014 · Stroke
  • Klaus K. Andersen · Christian Dehlendorff · Charlotte Skriver · [...] · Tom S. Olsen
    Article · Oct 2014 · Pharmacoepidemiology and Drug Safety
  • Source
    [Show abstract] [Hide abstract] ABSTRACT: Background A greater burden of stroke risk factors in general is associated with a higher risk for stroke among people of lower than those of higher socioeconomic position. The relative impact of individual stroke risk factors is still unclear. Methods and Results We studied the relations between socioeconomic position, measured as household income and length of education, and all hospital admissions for a first ischemic stroke among 54 048 people over the age of 40 years in Denmark in 2003–2012 in comparison with the general Danish population (23.5 million person‐years). We also studied the cardiovascular risk factor profile associated with socioeconomic position in stroke patients. Relative risks for stroke were estimated in log‐linear Poisson regression models. The risk for hospitalization for a first ischemic stroke was almost doubled for people in the lowest income group, and the risk of those of working age (<65 years) was increased by 36% among people with the shortest education. Diabetes, obesity, smoking, and high alcohol consumption in particular and, to a lesser extent, previous myocardial infarction or intermittent arterial claudication were significantly overrepresented among stroke patients with lower socioeconomic position. Atrial fibrillation and hypertension were not. Conclusions In Denmark, there is a strong relation between low socioeconomic position and risk for hospitalization for stroke. Lifestyle, as indicated by smoking, obesity, and alcohol consumption, and diabetes appears to increase the risk for stroke in people with lower socioeconomic position.
    Full-text available · Article · Jun 2014 · Journal of the American Heart Association
  • Christian Dehlendorff · Klaus K Andersen · Tom S Olsen
    [Show abstract] [Hide abstract] ABSTRACT: Importance Reports of an obesity paradox have led to uncertainty about secondary prevention in obese patients with stroke. The paradox is disputed and has been claimed to be an artifact due to selection bias.Objective To determine whether the obesity paradox in stroke is real or an artificial finding due to selection bias.Design, Setting, and Participants We studied survival after stroke in relation to body mass index (BMI, calculated as weight in kilograms divided by height in meters squared). To overcome selection bias, we studied only deaths caused by the index stroke on the assumption that death by stroke reported on a death certificate was due to the index stroke if death occurred within the first month poststroke. We used the Danish Stroke Register, containing information on all hospital admissions for stroke in Denmark from 2003 to 2012, and the Danish Registry of Causes of Death. The study included all registered Danes (n = 71 617) for whom information was available on BMI (n = 53 812), age, sex, civil status, stroke severity, stroke subtype, a predefined cardiovascular profile, and socioeconomic status.Main Outcomes and Measures The independent relation between BMI and death by the index stroke within the first week or month by calculating hazard ratios in multivariate Cox regression analysis and multiple imputation for cases for whom information on BMI was missing.Results Of the 71 617 patients, 7878 (11%) had died within the first month; of these, stroke was the cause of death of 5512 (70%). Of the patients for whom information on BMI was available, 9.7% were underweight, 39.0% were of normal weight, 34.5% were overweight, and 16.8% were obese. Body mass index was inversely related to mean age at stroke onset (P < .001). There was no difference in the risk for death by stroke in the first month among patients who were normal weight (reference), overweight (hazard ratio, 0.96; 95% CI, 0.88-1.04), and obese (hazard ratio, 1.0; 95% CI, 0.88-1.13). Analysis of deaths within 1 week gave similar results.Conclusions and Relevance We found no evidence of an obesity paradox in patients with stroke. Stroke occurred at a significantly younger age in patients with higher BMI. Hence, obese patients with stroke should continue to aim for normal weight.
    Article · Jun 2014 · JAMA Neurology
  • Christian Dehlendorff · Klaus Kaae Andersen · Tom Skyhøj Olsen
    [Show abstract] [Hide abstract] ABSTRACT: We studied the association between age and survival after stroke. We particularly focused on deaths that could be attributed to the stroke lesion itself; that is, early death in severe stroke. A registry of all hospitalized stroke patients in Denmark included 93 897 patients with information on stroke severity (Scandinavian Stroke Scale [SSS] 0-58), computed tomography, cardiovascular risk, age, sex and fatality within 1 month. Using regression models, we constructed age trajectories of 3-days, 1-week, and 1-month case-fatality rates unadjusted and adjusted for stroke severity, sex, and cardiovascular risk factors for patients with SSS <25 and SSS ≥25. The 3-days, 1-week, and 1-month case-fatality were 3.6%, 5.8% and 10.3%, respectively. Age-trajectories (SSS <25): 3-days case-fatality rates increased to the age of 75 years. Case-fatality rates then declined (unadjusted model) or leveled off (adjusted model) as age increased. One-week case-fatality increased to the age of 85 years. Case-fatality then leveled off (unadjusted model) or continued to rise (adjusted model) as age increased. One-month case-fatality rates increased throughout the entire lifespan. Age-trajectories (SSS ≥25): the leveling off phenomenon was still present for 3-days case-fatality; however, it was less pronounced. Very early stroke case-fatality rates increasing to the age of 75-85 years subsequently leveled off or even declined with increasing age. Advanced age per se should not be seen as a disadvantage in terms of surviving stroke in the very acute phase. Geriatr Gerontol Int 2013; ●●: ●●-●●.
    Article · Oct 2013 · Geriatrics & Gerontology International
  • Klaus Kaae Andersen · Tom Skyhøj Olsen
    [Show abstract] [Hide abstract] ABSTRACT: Although obesity is associated with excess mortality and morbidity, mortality is lower in obese than in normal weight stroke patients (the obesity paradox). Studies now indicate that obesity is not associated with increased risk of recurrent stroke in the years after first stroke. We studied the association between body mass index (BMI) and stroke patient's risk of having a history of previous stroke (recurrent stroke). A registry designed to collect data on all hospitalized stroke patients in Denmark 2000-2010 includes 61,872 acute stroke patients with information on BMI in 38,506. Data include age, sex, civil status, stroke severity (Scandinavian Stroke Scale), computed tomography, and cardiovascular risk factors. There were 28,382 patients with complete covariate information. We used multiple logistic regression models on this data set to compare the risk of stroke being recurrent in the 4 BMI groups: underweight (BMI < 18.5), normal weight (BMI 18.5-24.9), overweight (BMI 25.0-29.9), and obese (BMI ≥ 30.0). Of the patients with complete covariate information, 22,811 (80.1%) had first-ever stroke; in 5571 patients (19.6%), stroke was recurrent. Multiple logistic regression analysis adjusting for age, stroke severity, sex, BMI, civil status, and cardiovascular risk factors showed that being obese and overweight in comparison with normal weight was associated with a significantly lower risk of stroke being recurrent (obese: odds ratio [OR] = .90, confidence interval [CI] .82-.98; overweight: OR = .89, CI .83-.96). Being underweight was associated with a significantly higher risk of stroke being recurrent (OR = 1.23; CI 1.06-1.43). The obesity paradox in stroke can be extended to include also stroke recurrence. Obese and overweight stroke patients had experienced less previous strokes than normal weight stroke patients.
    Article · Jul 2013 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
  • Tom Skyhøj Olsen · Klaus Kaae Andersen
    [Show abstract] [Hide abstract] ABSTRACT: Aim: Reports on centenarians with stroke have thus far been casuistic. We present clinical characteristics and 1-month mortality in 39 centenarians admitted to Danish hospitals with acute stroke within 2000-2010. Methods: A Danish stroke registry (2000-2010) contains information about 61 935 acute stroke patients among which 39 patients were centenarians. Data included age, sex, civil and housing status, stroke severity (Scandinavian Stroke Scale [SSS], 0 worst to 58 best), computed tomography scan, cardiovascular risk factors and death within 1 month after stroke. Data in centenarians were compared with similar data in stroke patients aged 40-69 years (n = 25 023), 70-79 years (n = 16 048), 80-89 years (n = 16 274) and 90-99 years (n = 3379). Results: Of the 39 centenarians, 87% were women, 82% were living alone and 64% were living in their own home before the stroke. In general, the prevalence of cardiovascular risk factors was lower in centenarians, particularly with regard to previous myocardial infarction, previous stroke and diabetes mellitus. Strokes were significantly more severe (SSS 25.4), and 1-month mortality (38.5%) was significantly higher in centenarians when compared with other age groups. Conclusion: Centenarians with stroke are from a cardiovascular standpoint healthier than their younger counterparts. Yet, strokes in centenarians are more severe and associated with very high mortality.
    Article · Mar 2013 · Geriatrics & Gerontology International
  • Klaus Kaae Andersen · Tom Skyhøj Olsen
    [Show abstract] [Hide abstract] ABSTRACT: BACKGROUND: Although associated with excess mortality and morbidity, obesity is associated with lower mortality after stroke. The association between obesity and risk of recurrent stroke is unclear. AIMS: The study aims to investigate the association in stroke patients between body mass index and risk of death and readmission for recurrent stroke. METHODS: An administrative Danish quality-control registry designed to collect a predefined dataset on all hospitalized stroke patients in Denmark 2000-2010 includes 45 615 acute first-ever stroke patients with information on body mass index in 29 326. Data include age, gender, civil status, stroke severity, computed tomography, and cardiovascular risk factors. Patients were followed up to 9·8 years (median 2·6 years). We used Cox regression models to compare risk of death and readmission for recurrent stroke in the four body mass index groups: underweight (body mass index < 18·5), normal weight (body mass index 18·5-24·9), overweight (body mass index 25·0-29·9), obese (body mass index ≥ 30·0). RESULTS: Mean age 72·3 years, 48% women. Mean body mass index 23·0. Within follow-up, 7902 (26·9%) patients had died; 2437 (8·3%) were readmitted because of recurrent stroke. Mortality was significantly lower in overweight (hazard ratio 0·72; confidence interval 0·68-0·78) and obese (hazard ratio 0·80; confidence interval 0·73-0·88) patients while significantly higher in underweight patients (hazard ratio 1·66; confidence interval 1·49-1·84) compared with normal weight patients. Risk of readmission for recurrent stroke was significantly lower in obese than in normal weight patients (hazard ratio 0·84; confidence interval 0·72-0·92). CONCLUSIONSX: Obesity was not only associated with reduced mortality relative to normal weight patients. Compared with normal weight, risk of readmission for recurrent stroke was also lower in obese stroke patients.
    Article · Mar 2013 · International Journal of Stroke
  • T. S. Olsen · C. Dehlendorff · K. K. Andersen
    Article · Jan 2013 · Cerebrovascular Diseases
  • T. S. Olsen · K. K. Andersen
    Article · Jan 2013 · Cerebrovascular Diseases
  • [Show abstract] [Hide abstract] ABSTRACT: We estimated the costs to the Danish National Health Service of preventing stroke due to carotid artery stenosis by carotid endarterectomy (CEA), including costs of identifying patients, Doppler ultrasound (DUS) examination and CEA. Estimations are based on patients with stroke, transient ischemic attacks (TIA) or amaurosis fugax referred for carotid DUS in the municipality of Frederiksberg, Denmark (127,184 residents), within an 18-month period in 2008-2009. In total, 372 patients with stroke (n = 194), TIA (n = 157) or amaurosis fugax (n = 21) were referred for DUS. We identified 12 patients with 50-70% stenosis and 20 patients with >70% stenosis. Six had CEA, all of whom had stenosis >70%. Waiting time from symptom to CEA was a median of 38 days. Costs of preventing 1 recurrent stroke in the study period [number needed to treat (NNT) = 13] was in the range of EUR 207,675-333,918. If CEA had been performed within 2 weeks after onset of symptoms (NNT = 4), costs would be in the range of EUR 63,900-102,744. Costs of preventing stroke by CEA were high. Substantial reductions of costs (by about 2/3) can be achieved if CEA is performed <2 weeks after the ischemic event.
    Article · Jun 2012 · European Neurology
  • [Show abstract] [Hide abstract] ABSTRACT: We investigated cause-specific mortality in relation to age, sex, stroke severity, and cardiovascular risk factor profile in the Copenhagen Stroke Study cohort with 10 years of follow-up. In a Copenhagen community, all patients admitted to the hospital with stroke during 1992-1993 (n = 988) were registered on admission. Evaluation included stroke severity, computed tomography scan, and a cardiovascular risk profile. Cause of death within 10 years according to death certificate information was classified as stroke, heart/arterial disease, or nonvascular disease. Competing-risks analyses were performed by cause-specific Cox regression after multiple imputation of missing data, assuming that values were missing at random. Death was due to stroke in 310 patients (31%), to heart/arterial disease in 209 patients (21%), and to nonvascular diseases in 289 patients (29%); 180 patients were still alive after 10 years (18%). Stroke was the dominant cause of death during first year, with an absolute risk of 20.2% versus 5.2% for heart/arterial disease and 6.5% for nonvascular disease. The subsequent absolute risk of death per year was 2.8% for stroke, 4.5% for heart/arterial disease, and 5.2% for nonvascular disease. Death after stroke was associated with older age, male sex, greater stroke severity, and diabetes regardless of the cause of death. Previous stroke and hemorrhagic stroke were associated with death by stroke, ischemic heart disease was associated with death by heart/arterial disease and atrial fibrillation was associated with death by cardiovascular disease (stroke or heart/arterial disease). Hypertension, smoking, and alcohol consumption were not associated with cause-specific death.
    Article · May 2012 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    [Show abstract] [Hide abstract] ABSTRACT: Women who survive stroke are more disabled and more often institutionalized than men. We explore this phenomenon by studying case fatality and stroke severity in stroke survivors separately for men and women. A Danish stroke registry (2000-2007) contains information about 26,818 patients with first-ever ischemic stroke, including stroke severity (Scandinavian Stroke Scale, 0 worst to 58 best), computed tomography scan, cardiovascular risk factors, and death 3 months after stroke. We modeled stroke severity by generalized additive linear model and 3-month case fatality with logistic model adjusting for age and cardiovascular risk factors. Male to female ratio was 51.5% to 48.5%. Mean age was 68.8 (SD 12.6) years in men; 73.7 (13.8) years in women. Stroke was more severe in women (mean [SD] Scandinavian Stroke Scale, 42.2 [16.0]) than in men (mean [SD] Scandinavian Stroke Scale, 45.6 [14.2]) also after adjustment for age and cardiovascular risk factors; significant in patients older than 75 years. In survivors at 3 months, stroke was more severe in women than men, given same age and cardiovascular risk factor profile; significant in patients older than 75 years. More women (11.9%) had died within 3 months than men (8.6%). However, adjusting for age, stroke severity, and risk factor profile, 3-month case fatality was lower in women than men; significant in patients older than 78 years. Although 3-month case fatality was lower in women than men, strokes were more severe among survivors at 3 months in women than in men. In addition, strokes were more severe in women. Our data help elucidate why women survive stroke better but have poorer functional outcomes that require more care than men.
    Full-text available · Article · Apr 2012 · Gender Medicine
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    [Show abstract] [Hide abstract] ABSTRACT: Background. Higher fasting blood glucose (FBG) concentrations in the hyperglycemic range are associated with more severe strokes. Whether this association also extends into patients with FBG in the normoglycemic range is unclear. We studied the association of stroke severity and FBG in normoglycemic patients with ischemic stroke in a median of 7 days after stroke when the initial glycemic stress response has resolved. Method and Material. Included were 361 nondiabetic ischemic stroke patients with admission fasting blood glucose within 70-130 mg/dL admitted into an acute stroke rehabilitation unit in a median of 7 days after stroke. Data including neuroimaging, vital signs, cardiovascular risk factors, and admission functional independence measure (AFIM) were recorded prospectively. Results. FBG correlated with stroke severity in the normoglycemic 70-130 mg/dL range (FBG-AFIM correlation coefficient -0.17; P = 0.003). Odds ratio for more severe injury (below average AFIM score) was 2.02 for patients with FBG 110-130 mg/dL compared to FBG 70-90 mg/dL (95% confidence interval 1.10-3.73, P = 0.022). Each mg/dL increase in FBG was associated with an average decrease of 0.25 FIM points. In a multiple linear regression model, FBG was associated with more severe stroke (P = 0.002). Conclusion. One week after ischemic stroke, FBG within the normoglycemic range was associated with stroke severity.
    Full-text available · Article · Mar 2012 · Stroke Research and Treatment

Publication Stats

4k Citations

Institutions

  • 2010
    • Danish Cancer Society
      København, Capital Region, Denmark
  • 2009
    • Chang Gung Memorial Hospital
      T’ai-pei, Taipei, Taiwan
    • Glostrup Hospital
      København, Capital Region, Denmark
  • 1984-2009
    • Bispebjerg Hospital, Copenhagen University
      • Department of Neurology
      København, Capital Region, Denmark
  • 2007
    • Hillerød Hospital
      Hillerød, Capital Region, Denmark
  • 2001
    • Universität Heidelberg
      • Clinik of Neurology
      Heidelberg, Baden-Wuerttemberg, Germany