Cognitive function in young men and the later risk of fractures.

Dementia has been associated with an increased risk of fractures. These associations may be explained by an impaired cognitive function, as well as comorbid illness and toxic reaction from drugs. To investigate whether cognitive function in young, healthy individuals already affects the risk of fractures, overall cognitive function scores were calculated from four cognitive tests accomplished during a national conscriptions test in 960,956 men with a mean age of 18 years. Incident fractures were searched in national registers. During a median follow-up of 30 years (range 0 to 41 years), 65,313 men had one fracture and 2589 men had a hip fracture. Compared with men with no fracture, overall cognitive function at baseline was 3.5% lower for men sustaining one fracture and 5.5% lower for men sustaining a hip fracture (p < 0.001 for both). When comparing the lowest and the highest decile, low overall cognitive function scores increased the risk one fracture (hazard ratio [HR] = 1.55, 95% confidence interval [CI] 1.50-1.61) and a hip fracture (HR = 2.12, 95% CI 1.77-2.55), after adjustment for confounders. A higher education (university level versus elementary school) was associated with a decreased risk of a fracture (HR = 0.67, 95% CI 0.65-0.69) and a hip fracture (HR = 0.51, 95% CI 0.45-0.57). The effects of education and cognitive function were reduced when also adjusting for total income and disability pension. In summary, low cognitive function and education in young men were associated with the later risk of especially hip fractures. These associations may partly be mediated by socioeconomic factors.