Introduction

Sjögren disease (SjD) is a chronic systemic autoimmune disorder characterized by lymphocytic infiltration of exocrine glands, leading to xerostomia and keratoconjunctivitis sicca. In addition to glandular involvement, the disease may affect multiple extraglandular systems, including musculoskeletal, cutaneous, gastrointestinal, pulmonary, cardiac, endocrine, renal, hematologic, obstetric, and nervous systems [1, 2]. When SjD occurs in isolation, it is referred to as primary Sjögren disease (pSjD), whereas its coexistence with other autoimmune disorders such as systemic lupus erythematosus, rheumatoid arthritis, or systemic sclerosis is defined as associated Sjögren disease [3]. pSjD is among the most common autoimmune diseases, with an estimated prevalence ranging from 0.06 to 1.5%. It predominantly affects women, with a female-to-male ratio of approximately 10:1, and typically presents in the fifth to sixth decades of life [4]. Beyond glandular symptoms, pSjD is associated with a substantial burden of fatigue, pain, depression, anxiety, and sleep disturbances, all of which contribute to impaired quality of life [2].

Medication adherence, defined as the extent to which a patient’s medication-taking behavior corresponds with agreed recommendations, is a key component of effective management in chronic rheumatic diseases. Suboptimal adherence has been consistently associated with poorer clinical outcomes, including higher disease activity, worse functional status, and increased healthcare utilization [5, 6]. In rheumatoid arthritis, nonadherence rates have been reported to range from 30 to 80%, depending on the assessment method, and have been linked to reduced treatment response and impaired long-term disease control [7]. Similarly, in systemic lupus erythematosus, between one-quarter and more than half of patients are considered nonadherent, a behavior associated with disease flares, organ damage, and reduced quality of life [8, 9]. Comparable patterns have been reported in axial spondyloarthritis, where approximately one-third to one-half of patients do not fully adhere to prescribed therapies, and patients’ illness perceptions and beliefs about medicines have been shown to be associated with adherence behavior [10, 11]. Recent publications have also emphasized that adherence-related problems are relevant across rheumatic diseases, including treatment compliance and persistence with biological therapies in rheumatoid arthritis and the association between medication adherence and health empowerment in gout [12, 13].

Despite the increasing recognition of adherence as an important aspect of disease management across rheumatology, data on medication adherence in pSjD remain limited. Available evidence is sparse and largely indirect. For example, a recent study evaluating hydroxychloroquine blood levels suggested that a considerable proportion of patients had subtherapeutic concentrations, indicating potentially suboptimal adherence [14]. However, prospective studies using patient-reported adherence measures and simultaneously evaluating clinical, psychological, and perceptual factors—particularly in prospective cohorts—are lacking.

In addition, it is important to distinguish between newly diagnosed disease and early disease, as symptom onset in SjD may precede diagnosis by several years. Therefore, patients classified as newly diagnosed may still represent a heterogeneous group in terms of disease duration and burden.

While the relationship between medication beliefs and adherence has been studied in several rheumatic diseases, data addressing this relationship specifically in pSjD are scarce, particularly in newly diagnosed cohorts in which adherence, medication beliefs, systemic disease activity, Sjögren-specific symptoms, and patient-reported outcomes are evaluated together.

Accordingly, the present study aimed to evaluate medication adherence during follow-up in patients with newly diagnosed pSjD and to examine its associations with clinical characteristics, patient-reported outcomes, and beliefs about medicines.