ACR Meeting Abstracts

ACR Meeting Abstracts

Abstract Number: 583

Familial Aggregation and Heritability of Ankylosing Spondylitis in Taiwan: A Nationwide Population Study

Chang-Fu Kuo1, Matthew J. Grainge2, Lai-Chu See3, Kuang-Hui Yu4, Shue-Fen Luo4, Ana M. Valdes5, I-Jun Chou6, Weiya Zhang1 and Michael Doherty7, 1Academic Rheumatology, School of Clinical Sciences, University of Nottingham, Nottingham, United Kingdom, 2Division of Epidemiology and Public Health, School of Community Health Sciences, University of Nottingham, Nottingham, United Kingdom, 3Department of Public Health, College of Medicine, Chang Gung University, Taoyuan, Taiwan, 4Division of Rheumatology, Immunology and Allergy, Chang Gung Memorial Hospital, Taoyuan, Taiwan, 5Dept of Twin Research and Genetic Epidemiology, St. Thomas' Hospital, King's College London, London, United Kingdom, 6Department of Pediatrics, Chang Gung Memorial Hospital, Taoyuan, Taiwan, 7Academic Rheumatology, University of Nottingham, Nottingham, United Kingdom

Meeting: 2012 ACR/ARHP Annual Meeting

Keywords: ,

Session Information

Title: Spondylarthritis and Psoriatic Arthritis - Pathogenesis, Etiology

Session Type: Abstract Submissions (ACR)

Background/Purpose: To estimate the risk of ankylosing spondylitis (AS) among individuals with affected first-degree relatives and to assess the magnitude of genetic contribution to the susceptibility of AS in the general population of Taiwan.

Methods: Using data from the National Health Insurance Research Database in Taiwan, we conducted a nationwide cross-sectional study in 11,770,921 men and 11,697,080 women in 2004. The case definition of AS was based on physician diagnosis. The relative risk (RR) was calculated as the prevalence of AS among individuals with affected first-degree relatives, divided by the prevalence of AS among individuals with no affected first-degree relatives. The identification of first-degree relatives of each individual was determined using the NIHRD registry for beneficiaries. The marginal Cox proportional hazard model with an equal follow-up time for all subjects was used to estimate RR and the 95% confidence interval (CI). This model was used to account for shared environment and case clustering within families with robust variance, and to adjust for age, sex, place of residence, income levels and occupation. Heritability was calculated based on multifactorial polygenic model.

Results: There were 82,618 men (0.70%) and 58,445 women (0.50%) who had AS diagnosis in 2004. The prevalence of AS was higher in individuals with affected first-degree relatives (3.28%) than those without (0.58%). The overall familial relative risk (RR) was 7.95 (95% CI, 7.68–8.24). The RRs (95% CIs) for an individual with an affected twin, sibling, parent and offspring were 21.70 (18.75–25.11), 15.07 (14.78–16.13), 6.98 (6.66–7.32) and 6.77 (6.50–7.06) respectively. The RR (95% CI) increased with the number of affected first-degree relatives, from 7.35 (7.10–7.62), 43.00 (38.77–47.70) and 141.85 (103.50–194.41) for one, two or three, or more affected relatives, respectively. The heritability of AS was 0.95 (95% CI, 0.92–0.98). Among individuals with AS, only 4.16% had a family history. The population attributable risk associated with familial aggregation in Taiwan was 3.73% (95% CI, 4.24%–4.59%).

Conclusion: The risk of AS is higher among individuals with affected first-degree relatives. In addition, the heritability of AS is very high in the general population in Taiwan, confirming that genetic predisposition plays a major role in AS susceptibility.

Disclosure:

C. F. Kuo,
None;

M. J. Grainge,
None;

L. C. See,
None;

K. H. Yu,
None;

S. F. Luo,
None;

A. M. Valdes,
None;

I. J. Chou,
None;

W. Zhang,
None;

M. Doherty,
None.

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