Objectively measured physical activity predicts arterial stiffness in women independent of traditional and female-specific risk factors: evidence from the UK Biobank cohort

Background and purpose Arterial stiffness (AS) and carotid intima-media thickness (CIMT) are critical markers of vascular health that independently predict cardiovascular (CV) mortality. While physical activity (PA) is the cornerstone of CV risk reduction, most evidence relies on self-reported measures prone to recall bias and measurement error. Moreover, CV risk in women is influenced not only by traditional risk factors but also female-specific factors, such as reproductive and hormonal status. Accordingly, we investigated whether PA is independently associated with AS/CIMT in women beyond these risk factors by examining the association of both accelerometer-measured and self-reported PA with vascular outcomes. Methods We included all women from the UK Biobank who were free of any cardiovascular disease (CVD) and had completed PA and vascular assessments. Women whose PA was assessed after imaging were excluded. PA was measured both objectively using wrist-worn accelerometers (2013-2015, n = 8640/7582 for CIMT/AS) and self-reported IPAQ questionnaires (2006-2010, n = 19,088/17,022 for CIMT/AS). Vascular health was assessed using the arterial stiffness index (ASI) and CIMT (2014+). ASI was also measured at baseline (2006-2010); therefore, it was included as a covariate in ASI models to account for prior vascular status. Multivariable linear regression models examined associations between PA and vascular outcomes, adjusting for traditional CV risk factors. Further adjustment for female specific risk factors (menopause status, hormone replacement therapy (HRT), and pregnancy adverse events) was performed in a subgroup with available data (~85%). Results Accelerometer measured PA was significantly associated with lower ASI after adjustment for traditional risk factors (β = -0.028, p = 0.04). Each 1 SD increase in objective PA (~8.6 units) was associated with a decrease in ASI of 0.24 (95% CI -0.47 to -0.01). The association remained significant after additional adjustment for female-specific risk factors (β = -0.037, p = 0.015) and a reduced ASI by 0.32 (95% CI -0.58 to -0.06) was observed per 1 SD increase in accelerometer PA. No significant associations were found between self-reported PA and ASI. In our fully adjusted models, mean CIMT showed no significant association with either objective or self-reported PA. Age and LDL cholesterol were the strongest predictors of mean CIMT. Similarly, no significant association was observed between maximum CIMT and PA. Conclusion In women, objectively measured PA was inversely associated with ASI but not CIMT, independent of traditional and female-specific CV risk factors. Our findings highlight the importance of multi-modal CVD prevention strategies for women.