Background Ankylosing spondylitis (AS) affects physical function and health related quality of life. Depression has been reported to be frequent in AS patients. However, available epidemiological data are limited and estimates of the potentially increase in risk are lacking.
Objectives To compare the rate of doctor-diagnosed depression in a well-defined cohort of AS patients to the general health-care seeking population.
Methods The Skåne Health Care Register comprises data from each single health care consultation in the Skåne County, Sweden (population 1.2 million). Data include information about date of consultation and all ICD-10 diagnoses. Linking this register to the Swedish population register adds data regarding death and residency. We studied all patients who were registered with an AS diagnosis (ICD-10 code M45) at least once during 4 calendar years (2004 to 2007). To obtain depression rates we calculated the person-time from the day after the first occurrence of the AS diagnosis within the study period until the day of diagnosis of depression (F32 or F33) or another censoring event (death/relocation). We then obtained standardized depression-rate ratios by dividing the observed depression rate in AS patients by the expected rate based on the corresponding age- and sex specific rates of doctor-diagnosed depression in the general population of the county seeking care (reference population). A ratio >1 equals a higher rate of depression among AS patients than in the reference population of corresponding age and sex distribution.
Results We identified 935 AS patients, 67.2% men, mean age (SD) 52.3 (14.8) years. The reference population consisted of 761,210 subjects. During the 4-year observation period 10% (n=94) of the AS cohort had a doctor-diagnosed depression compared to 7% (n=66) to be expected based on data from the reference population. The standardized depression-rate ratio in men (1.41, 95% CI 1.04–1.87) and women with AS (1.43, 95% CI 1.05–1.91) were both significantly elevated in the same order of magnitude (Table).
Conclusions The rate of doctor-diagnosed depression was increased by about 40% in both male and female AS patients compared to the general population seeking care. Future challenges are to identify and treat the AS patients who suffer from depression as early as possible.
Disclosure of Interest None Declared