Haakon Lindekleiv

Incidence and mortality of aneurysmal subarachnoid hemorrhage in two Norwegian cohorts, 1984–2007

Objective: The incidence of aneurysmal subarachnoid hemorrhage (aSAH) ranges from 4 to 10 per 100,000 person-years in most countries, and 30-day case fatality is high. The aim of this study was to estimate the incidence and case fatality of aSAH and to assess preictal predictors of survival in 2 large Norwegian population-based cohort studies. Methods: A total of 94,976 adults (≥20 years) in the Nord-Trøndelag Health Study and 31,753 participants (aged ≥20 years) in the Tromsø Study were included. During follow-up, aSAHs were identified, incidence rates were estimated, and predictors of survival were assessed using Cox and Poisson regression analysis. Results: A total of 214 patients with aSAH were identified during 2,077,927 person-years of follow-up from 1984 to 2007. The incidence rate was 10.3 per 100,000 person-years: 13.3 for women and 7.1 for men. The incidence increased by 2% (95% confidence interval [CI] 0–4) per 5-year time period. Case fatality at 3, 7, and 30 days was 20%, 24%, and 36%. Thirty-day case fatality remained stable during follow-up (odds ratio 1.01, 95% CI 0.97–1.06 per year). Never smokers had poorer survival after aSAH than current and former smokers combined (hazard ratio 1.6, 95% CI 0.9–2.9). Conclusions: The slight increase in incidence of aSAH over time may be explained by differences in diagnostic procedures. Case fatality remained stable during 23 years of follow-up.

Sex differences in intracranial arterial bifurcations

BACKGROUND Subarachnoid hemorrhage (SAH) is a serious condition, occurring more frequently in females than in males. SAH is mainly caused by rupture of an intracranial aneurysm, which is formed by localized dilation of the intracranial arterial vessel wall, usually at the apex of the arterial bifurcation. The female preponderance is usually explained by systemic factors (hormonal influences and intrinsic wall weakness); however, the uneven sex distribution of intracranial aneurysms suggests a possible physiologic factor-a local sex difference in the intracranial arteries. OBJECTIVE The aim of this study was to explore sex variation in the bifurcation anatomy of the middle cerebral artery (MCA) and internal carotid artery (ICA), and the subsequent hemodynamic impact. METHODS Vessel radii and bifurcation angles were measured in patients with MCA and ICA bifurcations. Data from a previously published study of 55 patients undergoing diagnostic cerebral digital subtraction angiography at Dalcross Private Hospital in Sydney, Australia, between 2002 and 2003, were available for analysis. The measurements were used to create idealized, averaged bifurcations of the MCA and ICA for females and males. Computational fluid dynamics simulations were performed to calculate hemodynamic forces in the models. RESULTS The vessel radii and bifurcation angles of 47 MCA and 52 ICA bifurcations in 49 patients (32 females, 17 males; mean age, 53 years; age range, 14-86 years) were measured. Statistically significant sex differences were found in vessel diameter (males larger than females; P < 0.05), but not in bifurcation angle. Computational fluid dynamics simulations revealed higher wall shear stress in the female MCA (19%) and ICA (50%) bifurcations compared with the male bifurcations. CONCLUSIONS This study of MCA and ICA bifurcations in female and male patients suggests that sex differences in vessel size and blood flow velocity result in higher hemodynamic forces acting on the vessel wall in females. This new hypothesis may partly explain why intracranial aneurysms and SAH are more likely to occur in females than in males.

Prevalence of Age-related Macular Degeneration in Elderly Caucasians: The Tromsø Eye Study

PURPOSE To describe the sex- and age-specific prevalence of drusen, geographic atrophy, and neovascular age-related macular degeneration (AMD). DESIGN Population-based, cross-sectional study. PARTICIPANTS Caucasian adults aged 65 to 87 years from the 6th Tromsø Study, a population-based study conducted in 2007-2008 in the municipality of Tromsø, Norway. METHODS Digital color fundus photographs were graded for predominant phenotype based on drusen size, geographic atrophy, and neovascular AMD. MAIN OUTCOME MEASURES Age-related macular degeneration. RESULTS A total of 3025 subjects participated; 89% of those were invited to the eye examinations. Gradable photographs were available for 2631 persons (mean age 72.3 years). Drusen 63-125 μm as the predominant phenotype were found in 34.9% of participants (95% confidence interval [CI], 33.1-36.8), drusen >125 μm were found in 24.1% (95% CI, 22.5-25.8), geographic atrophy was found in 1.0% of participants (95% CI, 0.6-1.4), and neovascular AMD was found in 2.5% of participants (95% CI, 1.9-3.1). Bilateral involvement of late AMD was present in 1.1% of the sample. Eyes with late AMD had a significantly lower refractive error (spherical equivalent 0.078 vs. 0.99 diopters, P<0.0001), and 42.5% of eyes had Snellen visual acuity ≤ 0.32. CONCLUSIONS The prevalence of AMD among the elderly persons in this study was similar to rates in other Caucasian populations. Late AMD was present in 10.9% of subjects aged 80 years or more. No sex differences in prevalence rates of large drusen or late AMD were observed. Lower refractive error was observed in eyes with late AMD than in eyes without late AMD.

Sex differences in risk factors for aneurysmal subarachnoid hemorrhage: a cohort study.

Objective: The purpose of this study was to investigate sex differences in the major established risk factors for aneurysmal subarachnoid hemorrhage (aSAH) in a large, population-based cohort. Methods: Sex differences in the established risk factors for aSAH (smoking, hypertension, and alcohol consumption) were examined in a prospective, population-based cohort consisting of 92,462 participants of the Nord-Trøndelag and the Tromsø Health Studies in Norway. Results: We identified 120 cases of aSAH during 1,002,148 person-years at risk. Compared with the risk in nonsmokers, the risk of aSAH was higher in current cigarette-smoking women than in men (hazard ratio = 8.9, 95% confidence interval [CI] 4.7–17.0 vs hazard ratio = 2.8, 95% CI 1.3–6.1, after adjustment for age and alcohol consumption). The interaction between sex and current smoking was present on an additive scale (relative excess risk due to interaction 3.1, 95% CI 0.5–5.8), indicating a higher risk of aSAH associated with current cigarette smoking in women than in men. No sex differences in the risk of aSAH were observed with respect to hypertension or alcohol consumption. Conclusions: This prospective, population-based cohort study showed that compared with the risk in nonsmokers, the risk of aSAH was higher in current cigarette-smoking women than in men. This finding may at least partially explain the gender gap in aSAH incidence. A more intensive smoking cessation intervention should be considered in women at risk of aSAH.

Cardiovascular risk factors associated with age-related macular degeneration: the Tromso Study

To examine associations between cardiovascular risk factors and age‐related macular degeneration (AMD).

Joint Effect of Modifiable Risk Factors on the Risk of Aneurysmal Subarachnoid Hemorrhage: A Cohort Study

Background and Purpose— The joint effect of risk factors on the risk of aneurysmal SAH (aSAH) has been studied sparsely. Methods— We examined the potential synergism between cigarette smoking, hypertension, and regular alcohol consumption and the risk of aSAH in a prospective, population-based cohort of participants from the Nord-Trøndelag Health Study and the Tromsø Study in Norway. Interaction was assessed on additive and multiplicative scales. Results— We identified 122 cases of aSAH over 977 895 person-years of follow-up. Interaction was observed between current smoking and hypertension on the additive scale, (relative excess risk because of interaction, 6.40; 95% CI, 0.88–11.92, adjusted for sex and age). We found no significant interaction between hypertension and regular alcohol consumption or current cigarette smoking and regular alcohol consumption on the additive scale. No significant interaction was detected on the multiplicative scale. Conclusions— The joint effect of current smoking and hypertension on the risk of aSAH was stronger than was the sum of the independent effects of each factor. Persons at risk of aSAH should be advised of a markedly stronger risk for aSAH with the combination of current smoking and hypertension. In addition, the finding suggests that combining smoking cessation and blood pressure lowering may have an extra risk reduction effect on preventing aSAH.

Echocardiographic Screening of the General Population and Long-term Survival: A Randomized Clinical Study

IMPORTANCE Identification of structural heart disease in asymptomatic individuals could allow early disease-modifying treatment. OBJECTIVE To examine whether echocardiographic screening in the general population improves long-term survival or reduces the risk of cardiovascular disease. DESIGN, SETTING, AND PARTICIPANTS We studied 6861 middle-aged participants from the population-based Tromsø Study in Norway. INTERVENTION Participants were randomly allocated to an echocardiographic screening group (n = 3272) or a control group (n = 3589). MAIN OUTCOMES AND MEASURES Using the as-treated approach, the data were analyzed for mortality and incidence of fatal and nonfatal myocardial infarction and stroke. RESULTS During 15 follow-up years, 880 persons (26.9%) in the screening group and 989 persons (27.6%) in the control group died (hazard ratio, 0.97; 95% CI, 0.89-1.06). No significant differences between the groups were observed in the secondary outcome measures (sudden death, mortality from any heart disease, or incidence of fatal and nonfatal myocardial infarction and stroke). CONCLUSIONS AND RELEVANCE Echocardiographic screening for structural and valvular heart disease in the general population provided no benefit for mortality or for the risk of myocardial infarction or stroke.

Projected prevalence of age-related macular degeneration in Scandinavia 2012–2040

Purpose:  To project the number of persons with late age‐related macular degeneration (AMD) in Scandinavia through 2040.

Tromsø eye study: prevalence and risk factors of diabetic retinopathy

Purpose:  To determine the prevalence of visual impairment, retinopathy and macular oedema, and assess risk factors for retinopathy in persons with diabetes.

Risk factors for aneurysmal subarachnoid hemorrhage – BMI and serum lipids: 11‐year follow‐up of the HUNT and the Tromsø Study in Norway

Sandvei MS, Lindekleiv H, Romundstad PR, Müller TB, Vatten LJ, Ingebrigtsen T, Njølstad I, Mathiesen EB, Vik A. Risk factors for aneurysmal subarachnoid hemorrhage – BMI and serum lipids: 11‐year follow‐up of the HUNT and the Tromsø Study in Norway. 
Acta Neurol Scand: 2012: 125: 382–388. 
© 2011 John Wiley & Sons A/S.