Background/Purpose: Epidemiologic studies have linked osteoarthritis (OA) to atheromatous vascular disease, both age-related diseases.  Systemic hypertension (HTN) is an important risk factor for cardiovascular disease and may also be for OA.  The objective of this study was to evaluate whether there is an association between HTN and prevalent knee OA and pain in the Osteoarthritis Initiative (OAI).

Methods: This is a longitudinal study of the OAI, a multi-center observational study of knee OA. Systolic (SBP) and extensive medication data were accumulated on participants at their OAI baseline,  12-, 24-, and 36- month visits.  Bilateral PA knee radiographs were taken at the OAI 48- month visit.  Central readers assessed radiographic OA severity, Kellgren and Lawrence (KL) grade (0-4).  WOMAC pain scores were assessed for both knees at the 48- month visit.  The greatest WOMAC score within one participant represented the maximal WOMAC score.  There may be a lag between exposure to HTN and development of OA; therefore, we evaluated a 4 year interval between exposure and outcome. We performed logistic regression of quartiles of baseline SBP and 48- month status of prevalent radiographic OA (KL > 2) in either knee.  We evaluated prevalent instead of incident knee OA to minimize the likelihood of right sided censorship.  We performed a least square means of the maximum WOMAC score by quartile of SBP.  The adjusted model included age, sex, and body mass index (BMI) as covariates.  To eliminate the influence of HTN treatments, we performed subgroup analyses of those not taking anti-HTN medications at the baseline visit.  To address the possibility that participants’ SBPs fluctuated over time, we performed a sensitivity analysis using mean SBP over the baseline, 12-, 24-, and 36- month OAI visits as the exposure.

Results: 3644 people were included with a mean age of 61.1 (9.1), mean BMI of 28.5 (2.7), 42% were male.  61% of participants were not on anti-HTN medications.  20%, 13%, 5%, and 1% were on 1, 2, 3, and > 4 anti-HTN medications.

	Outcome = Prevalent Knee OA			Outcome = Knee Pain
N = 3644	Prevalence of Knee OA by SBP Quartile	Unadjusted Odds Ratio (95% CI)	Odds Ratio (95% CI) Adjusted for Age, Sex, BMI	LS Means of Maximal WOMAC Score, Adjusted for Age, Sex, BMI, Rad OA status
SBP Quartile 1(76 – 112)	531/1031 (52%)	Referent	Referent	2.6 (2.4 – 2.8)
SBP Quartile 2 (114 – 122)	519/846 (61%)	1.5 (1.2 – 1.8)	1.2 (1.0 – 1.5)	2.8 (2.6 – 3.0)
SBP Quartile 3 (123 – 134)	586/865 (68%)	2.0 (1.6 – 2.4)	1.4 (1.2 – 1.7)	2.9 (2.7 – 3.1)
SBP Quartile 4 (135 – 210)	619/902 (69%)	2.1 (1.7 – 2.5)	1.3 (1.0 – 1.6)	3.2 (3.0 – 3.4)
		p-for trend       < 0.0001	p-for trend           = 0.006	p trend                = 0.0016

Table. Systolic blood pressure is associated with prevalent radiographic knee osteoarthritis and knee pain.  Logistic regression of SBP quartile and prevalent knee OA.  Least Squared Means of maximal WOMAC score by SBP quartiles, adjusted for age, sex, BMI, and radiographic OA status.

Sensitivity analyses of participants who did not report anti-HTN medications showed similar results, as did using mean SBP over baseline – OAI 36 month as the exposure.

Conclusion: To our knowledge, this is the first epidemiologic study to show elevated systemic blood pressure is associated with increased prevalence of knee OA and greater levels of knee pain. The associations were weakened when adjusting for age, sex, and BMI, but were still significant.  These findings suggest a new and promising avenue for research on disease modification as well as symptom control in knee OA.  Future epidemiologic studies are needed to confirm these findings.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/elevated-systemic-blood-pressure-is-associated-with-increased-prevalent-knee-osteoarthritis-and-knee-pain-data-from-the-osteoarthritis-initiative/