Oral Contraceptive Pill Use in Women with Ankylosing Spondylitis Is Associated with a Younger Age At Diagnosis

Dharini Mahendira¹, Arane Thavaneswaran², Adele Carty³, Nigil Haroon⁴, Ammepa Anton⁵, Laura A. Passalent⁶, Khalid A. Alnaqbi³, Laurie M. Savage⁷, Elin Aslanyan⁷ and Robert D. Inman⁸, ¹Rheumatology, St Michael's Hospital, Toronto, ON, Canada, ²Rheumatology, Toronto Western Hospital and University of Toronto, Toronto, ON, Canada, ³Rheumatology, Toronto Western Hospital, Toronto, ON, Canada, ⁴Medicine/Rheumatology, University Health Network, Toronto Western Research Institute, University of Toronto, Toronto, ON, Canada, ⁵Rheumatology, University Health Network, Toronto, ON, Canada, ⁶Allied Health, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada, ⁷Spondylitis Association of America, Van Nuys, CA, ⁸Dept of Medicine/Rheumatology, Toronto Western Research Institute, University Health Network and University of Toronto, Toronto, ON, Canada

Meeting: ACR/ARHP Annual Meeting 2012

Keywords: Ankylosing spondylitis (AS), diagnosis and women's health

Session Information

Title: Spondylarthropathies and Psoriatic Arthritis: Clinical Aspects and Treatment

Session Type: Abstract Submissions (ACR)

Background/Purpose: While AS is traditionally recognized as a predominantly male disease, the impact of gender differences on AS pathogenesis has not been clearly established. Specifically, the potential role of sex hormones in mediating gender impact on both AS susceptibility and disease severity remains unanswered. Both exogenous and endogenous estrogens may play a key role in AS disease expression in women. Our objective is to elucidate the potential impact of exogenous estrogen on AS initiation and severity. We hypothesized that exogenous estrogen, in the form of oral contraceptive pills (OCP), may alter AS disease activity and severity in premenopausal women.

Methods: The study population consists of premenopausal women with AS seen in our longitudinal clinic, as well as members of the Spondylitis Association of America (SAA). Measures of disease severity included: use of biological agents, hip replacement surgery, and BASFI scores as a surrogate marker of disability. A patient questionnaire was created and used to obtain information on patient demographics, past and present OCP use, menstrual history, pregnancy history, AS duration, medication use, and hip replacement.

Results: A total of 655 women participated in this study. This was comprised of 516 OCP users and 139 non-OCP users. The mean age of OCP users was 42.2 (+/- 11.5) and 47.9 (+/- 12.2) years in non-OCP users. While no difference was noted with respect to initial onset of back pain, OCP users were significantly younger at the age of diagnosis of AS (35.7 years vs. 38.6 years, p=0.01). (Table) There was no significant difference in anti-TNF or opioid use, pregnancy complications, nor rates of hip surgery between OCP and non-OCP users. A trend towards higher rate of pregnancy complications was noted in all OCP users, although this was not statistically significant (45.4% vs. 36.5%, p=0.13). There was no significant difference in reported BASFI scores between the groups.

Conclusion: The use of exogenous estrogens in the form of oral contraceptive pills is associated with a significantly earlier diagnosis of AS in women. To date, this is the largest study investigating the potential impact of exogenous estrogens in women with AS. While exogenous estrogens are not associated with surrogate indicators of disease severity, the earlier age of diagnosis of AS amongst women taking OCP suggests hormone modulation of disease expression in the early stages of disease.

Table: Women with AS – Clinical Features in OCP Users vs Non-users

	OCP Users (n=516)	Non-OCP Users (n=139)	P-value
Age at diagnosis of AS	35.7 (11.2)	38.6 (12.2)	0.01
Age at onset of back pain	24.1 (10.2)	24.7 (10.5)	0.52
Race (% Caucasian)	457 (90.7%)	112 (83.0%)	0.02
Use of Anti-TNF agents	330 (64%)	80 (58.4%)	0.23
Use of Opioids	186 (41.5%)	56 (45.5%)	0.47
Past hip surgery	20 (4.4%)	8 (6.5%)	0.34
Past pregnancy complications	152 (45.4%)	35 (36.5%)	0.13

Disclosure:

D. Mahendira,
None;

A. Thavaneswaran,
None;

A. Carty,
None;

N. Haroon,
None;

A. Anton,
None;

L. A. Passalent,
None;

K. A. Alnaqbi,
None;

L. M. Savage,
None;

E. Aslanyan,
None;

R. D. Inman,
None.

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