Intelligence in early adulthood and subsequent risk of unintentional injury over two decades: cohort study of 1 109 475 Swedish men
- 1MRC Social & Public Health Sciences Unit, University of Glasgow, Glasgow, UK
- 2Department of Psychology, Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK
- 3George Institute for International Health, University of Sydney, Sydney, New South Wales, Australia
- 4MRC Epidemiology Resource Centre, University of Southampton, Southampton, UK
- 5Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden
- Correspondence to Finn Rasmussen, Child and Adolescent Public Health Epidemiology Group, Department of Public Health Sciences, Karolinska Institute, SE-17176 Stockholm, Sweden;
Contributors All authors contributed to the design and interpretation of the study, drafted and critically revised the manuscript and approved the final version. EW conducted the statistical analyses and wrote the first draft. EW, PT and FR are the guarantors.
- Accepted 1 November 2009
- Published Online First 1 December 2009
Background There is growing evidence of an inverse association between intelligence (IQ) and unintentional injuries.
Methods Analyses are based on a cohort of 1 109 475 Swedish men with IQ measured in early adulthood. Men were followed up for an average 24 years, and hospital admissions for unintentional injury were recorded.
Results 198 133 (17.9%) men had at least one hospital admission for any unintentional injury during follow-up. The most common cause of unintentional injury was falling, followed by road accidents, poisoning, fire and drowning. In addition, 14 637 (1.3%) men had at least one admission for complications of medical care. After adjusting for confounding variables, lower IQ scores were associated with an elevated risk of any unintentional injury (HR (95% CI) per SD decrease in IQ: 1.15 (1.14 to 1.15)) and of cause-specific injuries other than drowning (poisoning (1.53 (1.49 to 1.57)), fire (1.36 (1.31 to 1.41)), road traffic accidents (1.25 (1.23 to 1.26)), medical complications (1.20 (1.18 to 1.22)) and falling (1.17 (1.16 to 1.18))). These gradients were stepwise across the full IQ range.
Conclusions Low IQ scores in early adulthood were associated with a subsequently increased risk of unintentional injury. A greater understanding of mechanisms underlying these associations may provide opportunities and strategies for prevention.
Funding DB is a Wellcome Trust Fellow (WBS U.1300.00.006.00012.01). The MRC Social and Public Health Sciences Unit receives funding from the UK Medical Research Council and the Chief Scientist Office at the Scottish Government Health Directorates. The Centre for Cognitive Ageing and Cognitive Epidemiology is supported by the Biotechnology and Biological Sciences Research Council, the Engineering and Physical Sciences Research Council, the Economic and Social Research Council, the Medical Research Council and the University of Edinburgh as part of the cross-council Lifelong Health and Wellbeing initiative.
Competing interest None.
Ethics approval This study was conducted with the approval of the Regional Ethics Committee, Stockholm.
Provenance and peer review Not commissioned; externally peer reviewed.