Tom Wilsgaard

A sequence variant in ZFHX3 on 16q22 associates with atrial fibrillation and ischemic stroke

We expanded our genome-wide association study on atrial fibrillation (AF) in Iceland, which previously identified risk variants on 4q25, and tested the most significant associations in samples from Iceland, Norway and the United States. A variant in the ZFHX3 gene on chromosome 16q22, rs7193343-T, associated significantly with AF (odds ratio OR = 1.21, P = 1.4 × 10−10). This variant also associated with ischemic stroke (OR = 1.11, P = 0.00054) and cardioembolic stroke (OR = 1.22, P = 0.00021) in a combined analysis of five stroke samples.

Cohort profile: The Tromsø Study

The Tromso Study was initiated in 1974 in an attempt to help combat the high mortality of cardiovascular diseases in Norway, that was particularly pronounced among middle-aged men. In the mid-1970s, Norwegian men had a 20% risk of dying of myocardial infarction (MI) before the age of 75 years. The situation in Northern Norway was even worse. The primary aim of the Tromso Study was to determine causes of the high cardiovascular mortality, and also to develop ways of preventing heart attacks and strokes. This was reflected through the first name of the study: The Tromso Heart Study. However, during the 37 years since the first examination of the Tromso Study took place, increasing emphasis has been put on other chronic diseases and conditions, in particular atrial fibrillation, venous thromboembolism, diabetes mellitus, osteoporosis and fractures. It has been a deliberate policy to invite a wide range of faculty research groups to join in with subprojects in the surveys, and there are currently some 100 different ongoing research projects based on the data from the consecutive six surveys. The study was initially funded by the University of Tromso, and has been so for the entire period since 1974, but there have also been substantial contributions, directly and indirectly from, for example, the National Screening Services, the Research Council of Norway, Northern Norway Regional Health Authority, Norwegian Council on Cardiovascular Diseases and Norwegian Foundation for Health and Rehabilitation. Teams of investigators approach public research programmes for funding of the different examinations conducted. Tromso is the largest city in Northern Norway. It is situated 400 km north of the Arctic Circle, and has approximately 67 000 inhabitants. The physical living conditions are dominated by dramatic changes in the light with 2 months of midnight sun and 2 months of the polar night. However, due to the Gulf Stream, the climate is relatively mild, the latitude (698N) taken into account.

Carotid Atherosclerosis Is a Stronger Predictor of Myocardial Infarction in Women Than in Men: A 6-Year Follow-Up Study of 6226 Persons: The Tromsø Study

Background and Purpose— Ultrasound of carotid arteries provides measures of intima media thickness (IMT) and plaque, both widely used as surrogate measures of cardiovascular disease. Although IMT and plaques are highly intercorrelated, the relationship between carotid plaque and IMT and cardiovascular disease has been conflicting. In this prospective, population-based study, we measured carotid IMT, total plaque area, and plaque echogenicity as predictors for first-ever myocardial infarction (MI). Methods— IMT, total plaque area, and plaque echogenicity were measured in 6226 men and women aged 25 to 84 years with no previous MI. The subjects were followed for 6 years and incident MI was registered. Results— During follow-up, MI occurred in 6.6% of men and 3.0% of women. The adjusted relative risk (RR; 95% CI) between the highest plaque area tertile versus no plaque was 1.56 (1.04 to 2.36) in men and 3.95 (2.16 to 7.19) in women. In women, there was a significant trend toward a higher MI risk with more echolucent plaque. The adjusted RR (95% CI) in the highest versus lowest IMT quartile was 1.73 (0.98 to 3.06) in men and 2.86 (1.07 to 7.65) in women. When we excluded bulb IMT from analyses, IMT did not predict MI in either sex. Conclusions— In a general population, carotid plaque area was a stronger predictor of first-ever MI than was IMT. Carotid atherosclerosis was a stronger risk factor for MI in women than in men. In women, the risk of MI increased with plaque echolucency.

Several common variants modulate heart rate, PR interval and QRS duration

Electrocardiographic measures are indicative of the function of the cardiac conduction system. To search for sequence variants that modulate heart rate, PR interval and QRS duration in individuals of European descent, we performed a genome-wide association study in ∼10,000 individuals and followed up the top signals in an additional ∼10,000 individuals. We identified several genome-wide significant associations (with P < 1.6 × 10−7). We identified one locus for heart rate (MYH6), four for PR interval (TBX5, SCN10A, CAV1 and ARHGAP24) and four for QRS duration (TBX5, SCN10A, 6p21 and 10q21). We tested for association between these loci and subjects with selected arrhythmias in Icelandic and Norwegian case-control sample sets. We observed correlations between TBX5 and CAV1 and atrial fibrillation (P = 4.0 × 10−5 and P = 0.00032, respectively), between TBX5 and advanced atrioventricular block (P = 0.0067), and between SCN10A and pacemaker implantation (P = 0.0029). We also replicated previously described associations with the QT interval.

Vitamin D and mortality: meta-analysis of individual participant data from a large consortium of cohort studies from Europe and the United States

Objective To investigate the association between serum 25-hydroxyvitamin D concentrations (25(OH)D) and mortality in a large consortium of cohort studies paying particular attention to potential age, sex, season, and country differences. Design Meta-analysis of individual participant data of eight prospective cohort studies from Europe and the US. Setting General population. Participants 26 018 men and women aged 50-79 years Main outcome measures All-cause, cardiovascular, and cancer mortality. Results 25(OH)D concentrations varied strongly by season (higher in summer), country (higher in US and northern Europe) and sex (higher in men), but no consistent trend with age was observed. During follow-up, 6695 study participants died, among whom 2624 died of cardiovascular diseases and 2227 died of cancer. For each cohort and analysis, 25(OH)D quintiles were defined with cohort and subgroup specific cut-off values. Comparing bottom versus top quintiles resulted in a pooled risk ratio of 1.57 (95% CI 1.36 to 1.81) for all-cause mortality. Risk ratios for cardiovascular mortality were similar in magnitude to that for all-cause mortality in subjects both with and without a history of cardiovascular disease at baseline. With respect to cancer mortality, an association was only observed among subjects with a history of cancer (risk ratio, 1.70 (1.00 to 2.88)). Analyses using all quintiles suggest curvilinear, inverse, dose-response curves for the aforementioned relationships. No strong age, sex, season, or country specific differences were detected. Heterogeneity was low in most meta-analyses. Conclusions Despite levels of 25(OH)D strongly varying with country, sex, and season, the association between 25(OH)D level and all-cause and cause-specific mortality was remarkably consistent. Results from a long term randomised controlled trial addressing longevity are being awaited before vitamin D supplementation can be recommended in most individuals with low 25(OH)D levels.

Outdoor activities and diet in childhood and adolescence relate to MS risk above the Arctic Circle

BackgroundA relationship between the latituderelated distribution of multiple sclerosis (MS) and exposure to sunlight has long been considered. Higher sun exposure during early life has been associated with decreased risk of MS.ObjectiveSince Norway is an exception to the latitude gradient of MS prevalence, we tested here whether sunlight exposure or vitamin D-related dietary factors in childhood and adolescence are associated with the risk of MS.MethodsRetrospective recall questionnaire data from 152 MS patients and 402 population controls born at and living at latitudes 66–71°N were analysed by means of conditional logistic regression analysis accounting for the matching variables age, sex, and place of birth.ResultsIncreased outdoor activities during summer in early life were associated with a decreased risk of MS, most pronounced at ages 16–20 years (odds ratio (OR) 0.55, 95% CI 0.39–0.78, p = 0.001, adjusted for intake of fish and cod-liver oil). A protective effect of supplementation with cod-liver oil was suggested in the subgroup that reported low summer outdoor activities (OR 0.57, 95% CI 0.31–1.05, p = 0.072). Consumption of fish three or more times a week was also associated with reduced risk of MS (OR 0.55, 95% CI 0.33–0.93, p = 0.024).ConclusionSummer outdoor activities in childhood and adolescence are associated with a reduced risk of MS even north of the Arctic Circle. Supplemental cod-liver oil may be protective when sun exposure is less, suggesting that both climate and diet may interact to influence MS risk at a population level.

Cardiovascular Risk Factors and Morbidity in Long-Term Survivors of Testicular Cancer: A 20-Year Follow-Up Study

PURPOSE To evaluate the prevalence of cardiovascular risk factors and long-term incidence of cardiovascular disease (CVD) in survivors of testicular cancer (TC). METHODS Overall, 990 men treated for unilateral TC (1980 to 1994) were included in this national follow-up study (2007 to 2008). They were categorized into four treatment groups: surgery (n = 206), radiotherapy only (RT; n = 386), chemotherapy only (n = 364), and combined RT/chemotherapy (n = 34). Age-matched male controls from the general population (ie, NORMs) were included (n = 990). Survivors of TC who were diagnosed with CVD before or within 2 years after the TC diagnosis were excluded from analyses of CVD end points. RESULTS Median observation time was 19 years (range, 13 to 28 years). All cytotoxic treatment groups had significantly increased prevalences of antihypertensive medication, and survivors in the RT and RT/chemotherapy groups had higher prevalences of diabetes (RT: odds ratio [OR], 2.3; 95% CI, 1.5 to 3.7; RT/chemotherapy: OR, 3.9; 95% CI, 1.4 to 10.9) compared with NORMs. Overall 74 survivors of TC (8.0%) experienced atherosclerotic disease during follow-up. Increased risks for atherosclerotic disease were observed in age-adjusted Cox regression analyses after any cytotoxic treatment when compared with surgery only (RT: hazard ratio [HR], 2.3; 95% CI, 1.04 to 5.3; chemotherapy: HR, 2.6; 95% CI, 1.1 to 5.9; RT/chemotherapy: HR, 4.8; 95% CI, 1.6 to 14.4). Treatment with cisplatin, bleomycin, and etoposide (BEP) alone had a 5.7-fold higher risk (95% CI, 1.9 to 17.1 fold) for coronary artery disease compared with surgery only and a 3.1-fold higher risk (95% CI, 1.2 to 7.7 fold) for myocardial infarction compared with NORMs. CONCLUSION Treatment with infradiaphragmatic RT and/or cisplatin-based chemotherapy, particularly the BEP regimen, increases the long-term risk for CVD in survivors of TC.

Carotid Plaque Area and Intima-Media Thickness in Prediction of First-Ever Ischemic Stroke A 10-Year Follow-Up of 6584 Men and Women: The Tromsø Study

Background and Purpose— Carotid plaque and intima-media thickness (IMT) are recognized as risk factors for ischemic stroke, but their predictive value has been debated and varies between studies. The purpose of this longitudinal population-based study was to assess the risk of ischemic stroke associated with plaque area and IMT in the carotid artery. Methods— IMT and total plaque area in the right carotid artery were measured with ultrasound in 3240 men and 3344 women aged 25 to 84 years who participated in a population health study in 1994 to 1995. First-ever ischemic strokes were identified through linkage to hospital and national diagnosis registries, with follow-up until December 31, 2005. Results— Incident ischemic strokes occurred in 7.3% (n=235) of men and 4.8% (n=162) of women. The hazard ratio for 1 SD increase in square-root-transformed plaque area was 1.23 (95% CI, 1.09–1.38; P=0.0009) in men and 1.19 (95% CI, 1.01–1.41; P=0.04) in women when adjusted for other cardiovascular risk factors. The multivariable-adjusted hazard ratio in the highest quartile of plaque area versus no plaque was 1.73 (95% CI, 1.19–2.52; P=0.004) in men and 1.62 (95% CI, 1.04–2.53; P=0.03) in women. The multivariable-adjusted hazard ratio for 1 SD increase in IMT was 1.08 (95% CI, 0.95–1.22; P=0.2) in men and 1.24 (95% CI, 1.05–1.48; P=0.01) in women. There were no differences in stroke risk across quartiles of IMT in multivariable analysis. Conclusions— In the present study, total plaque area appears to be a stronger predictor than IMT for first-ever ischemic stroke.

Mean platelet volume is a risk factor for venous thromboembolism: the Tromsø study

See also Machin SJ, Briggs C. Mean platelet volume: a quick, easy determinant of thrombotic risk? This issue, pp 146–7.

Drug-Eluting or Bare-Metal Stents for Coronary Artery Disease

BACKGROUND Limited data are available on the long-term effects of contemporary drug-eluting stents versus contemporary bare-metal stents on rates of death, myocardial infarction, repeat revascularization, and stent thrombosis and on quality of life. METHODS We randomly assigned 9013 patients who had stable or unstable coronary artery disease to undergo percutaneous coronary intervention (PCI) with the implantation of either contemporary drug-eluting stents or bare-metal stents. In the group receiving drug-eluting stents, 96% of the patients received either everolimus- or zotarolimus-eluting stents. The primary outcome was a composite of death from any cause and nonfatal spontaneous myocardial infarction after a median of 5 years of follow-up. Secondary outcomes included repeat revascularization, stent thrombosis, and quality of life. RESULTS At 6 years, the rates of the primary outcome were 16.6% in the group receiving drug-eluting stents and 17.1% in the group receiving bare-metal stents (hazard ratio, 0.98; 95% confidence interval [CI], 0.88 to 1.09; P=0.66). There were no significant between-group differences in the components of the primary outcome. The 6-year rates of any repeat revascularization were 16.5% in the group receiving drug-eluting stents and 19.8% in the group receiving bare-metal stents (hazard ratio, 0.76; 95% CI, 0.69 to 0.85; P<0.001); the rates of definite stent thrombosis were 0.8% and 1.2%, respectively (P=0.0498). Quality-of-life measures did not differ significantly between the two groups. CONCLUSIONS In patients undergoing PCI, there were no significant differences between those receiving drug-eluting stents and those receiving bare-metal stents in the composite outcome of death from any cause and nonfatal spontaneous myocardial infarction. Rates of repeat revascularization were lower in the group receiving drug-eluting stents. (Funded by the Norwegian Research Council and others; NORSTENT ClinicalTrials.gov number, NCT00811772 .).