Fish consumption and risk of stroke: a second prospective case-control study from northern Sweden

Wennberg et al. Nutrition Journal Fish consumption and risk of stroke: a second prospective case-control study from northern Sweden Maria Wennberg 0 3 Jan-Håkan Jansson 2 Margareta Norberg 1 Staffan Skerfving 7 Ulf Strömberg 6 Per-Gunnar Wiklund 5 Ingvar A. Bergdahl 4 8 0 Department of Public Health and Clinical Medicine, Nutritional Research, Umeå University , 901 87 Umeå , Sweden 1 Department of Public Health and Clinical Medicine, Epidemiology and Global Health, Umeå University , Umeå , Sweden 2 Department of Public Health and Clinical Medicine, Research Unit Skellefteå, Umeå University , Umeå , Sweden 3 Department of Public Health and Clinical Medicine, Nutritional Research, Umeå University , 901 87 Umeå , Sweden 4 Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine, Umeå University , Umeå , Sweden 5 Department of Public Health and Clinical Medicine, Medicine, Umeå University , Umeå , Sweden 6 Health Metrics Unit, The Sahlgrenska Academy, University of Gothenburg , Gothenburg , Sweden 7 Division of Occupational and Environmental Medicine, Lund University , Lund , Sweden 8 Department of Biobank Research, Umeå University , Umeå , Sweden Background: Fish consumption has been concluded to be associated with decreased risk of stroke in several reviews. However, among men, but not women, an increased risk of stroke was previously found at high fish consumption (>3 meals/week) in northern Sweden. This study investigates if previous results on elevated stroke risk with high fish consumption in men in northern Sweden can be confirmed in a larger study with new cases in the same population. Methods: A prospective nested case-control study was performed within the population-based Northern Sweden Health and Disease Study cohort. Information on fish consumption, other lifestyle and medical data was collected at baseline. Incident stroke cases (1987-2007, n = 735) were identified and 2698 controls matched for gender, age, year of baseline and geographical region. Results: There were no associations between total fish or fatty fish consumption and stroke risk; thus the previous finding of increased risk of stroke with high fish consumption in men could not be repeated. High intake of lean fish (>twice/week compared to < once/month) was associated with increased stroke risk in men [OR 1.80 (95% CI 1. 00, 3.21), but not in women [OR 0.50 (95% CI 0.24, 1.10)]. The association was driven by men living alone. Conclusions: The previous association between high total fish consumption and risk of stroke in men could not be repeated. The increased risk found in men with high intake of lean fish may be due to chance or confounding specific for this group. Fish consumption; Ischaemic stroke; Hemorraghic stroke; Lifestyle; Confounding - Introduction Fish consumption has been associated with protection against cardiovascular disease (CVD) in several epidemiological studies, reviewed by e.g. Wang et al. and Konig et al. [1, 2], and recently updated by Kromhout and de Goede [3]. Even though evidence is stronger for myocardial infarction, most reviews and meta-analyses indicate modest associations also between fish consumption and decreased risk of stroke [4–7]. However, we got conflicting results in our case-control study from northern Sweden [8], with an increased risk for stroke seen in men reporting fish consumption > 3 times/week as compared to those reporting fish consumption less than once a month, but no association for women. Lifestyle variables were not extensively adjusted for in that study; for example no information was presented for physical activity level or consumption of fruit and vegetables. A lifestyle study was therefore performed, examining associations between fish consumption and other health factors in over 60 000 men and women in the same region [9]. Fish consumption was associated with other healthy behaviors, such as non-smoking, high education, physical activity and higher consumption of fruit and vegetables, both in men and women. The only gender difference found was that high fish consumption was associated with consumption of all types of alcohol in men, but only with © The Author(s). 2016 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. consumption of wine in women. The study could thus not explain the finding of increased risk of stroke in male high-consumers of fish found by Wennberg et al. [8], but underlined th (...truncated)