Legg-Calvé-Perthes disease and the risk of ADHD, depression, and mortality: A registry study involving 4057 individuals

BACKGROUND AND PURPOSE: Hyperactive behavior pattern (such as attention deficit hyperactivity disorder (ADHD)) is proposed to be present in individuals with Legg-Calvé-Perthes disease (LCPD). We investigated whether individuals with LCPD have a higher risk of ADHD, depression, and mortality. SUBJECTS AND METHODS: We identified 4,057 individuals with LCPD in Sweden during the period 1964–2011. 40,570 individuals without LCPD were randomly selected from the Swedish general population and matched by year of birth, sex, and region (control group). We used Cox proportional hazard regression to estimate the relative risks. RESULTS: Compared to the control group, individuals with LCPD had a raised hazard ratio (HR) of 1.5 (95% CI: 1.2–1.9) for ADHD. The risks were higher for female individuals (HR = 2.1, CI: 1.3–3.5) than for male individuals (HR = 1.4, CI: 1.1–1.8). Individuals with LCPD had a modestly higher hazard ratio for depression (HR = 1.3, CI: 1.1–1.5) than the control group. Furthermore, individuals with LCPD had a slightly higher mortality risk than the control group (HR = 1.2, CI: 1.0–1.4) INTERPRETATION: Individuals with LCPD have a higher risk of ADHD. Hyperactivity could expose the femoral head to higher mechanical stress and contribute to the etiology of LCPD. The higher risk of depression may be due to the burden of LCPD itself or could reflect neurobehavioral aspects of ADHD changing into depression later in life. Individuals with LCPD have a higher mortality risk, with higher risk of suicide and cardiovascular diseases.