Mental distress and risk of hip fracture. Do broken hearts lead to broken bones?

OBJECTIVE Mental distress may entail increased risk of hip fracture, but it is uncertain whether the effect consists solely of an indirect effect through use of medication, or whether it is also mediated through other mechanism. The purpose of this study was to examine the association between mental distress and risk of hip fracture in women, adjusted for medication (that is, use of tranquillisers/sedatives or hypnotics). DESIGN A three year follow up of hip fracture was conducted on 18,612 women, consisting of 92.5% of all women aged 50 years or older in a Norwegian county. Three hundred and twenty nine suffered a hip fracture. A mental distress index was based on questions about life dissatisfaction, nervousness, loneliness, sleep disorders, troubled and uneasy feelings, depression and impairment attributable to psychological complaints. Relative risk with 95% confidence intervals (CI) of hip fracture with respect to mental distress were controlled for medication, age, body mass index (BMI), smoking, physical inactivity, and physical illness by means of Cox regression. RESULTS The 10% of women with the highest mental distress had more than twofold increased risk of hip fracture compared with the 10% of women with the lowest mental distress, after adjustment for age and medication. The relative risk was 1.95 (95% CI 1.2, 3.3) after additional control for BMI, smoking, physical inactivity, and physical illness. The relative risk of hip fracture for daily users of medication compared with never users was 2.1 (95% CI 1.6, 2.9). After adjusting for mental distress it was 1.5 (95% CI 1.0, 2.2). CONCLUSIONS Risk of hip fracture was positively related to mental distress, also after adjustment for medication use. The effect of tranquillisers/sedatives or hypnotics on hip fracture risk may be overestimated in studies with no adjustments for mental distress.