Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease that primarily affects intertriginous areas such as the axillae, groin, and anogenital region, where apocrine glands are concentrated (1, 2). It is characterized by recurrent, painful nodules, abscesses, sinus tracts, and scarring. Diagnosis is typically clinical, often utilizing the Hurley staging system to assess severity. Onset usually occurs in early adulthood, and HS can persist for decades, significantly impacting quality of life (1, 2). Global prevalence estimates vary widely (0.00033–4.1%) due to differences in diagnostic criteria, populations studied, and methodologies. Highest rates of HS are reported in Europe (1.4%), followed by North America (0.67%) and Asia (0.42%). HS is more common in women, with reported female-to-male ratios ranging from 1.5:1 to 4:1 (3–5).

Beyond its dermatologic manifestations, HS is increasingly recognized as a systemic condition associated with a wide range of comorbidities that affect multiple organ systems (2, 6, 7). Research has linked HS to various other illnesses, and demonstrated a strong association with components of metabolic syndrome, including obesity, dyslipidemia, hypertension, and type 2 diabetes mellitus (6–9). These conditions are significantly more prevalent in HS patients than in the general population: some studies have reported metabolic syndrome in up to 65% of individuals with HS, versus an estimated 10–25% in the general population (6, 7, 10). Obesity in particular is strongly linked to HS, potentially contributing to its pathogenesis through mechanical stress in skin folds and chronic systemic inflammation. Lipid abnormalities and insulin resistance may also exacerbate disease severity and progression (8, 10).

HS is associated with increased cardiovascular risk (11, 12). Elevated rates of hypertension, cerebrovascular disease, and peripheral vascular disorders have been observed in HS patients, potentially contributing to higher cardiovascular mortality (11, 12). Some studies estimate a 1.7-fold increased risk of cardiovascular-related death in individuals with HS (11, 12). While the independent contribution of HS to cardiovascular risk remains unclear, the frequent co-occurrence of metabolic comorbidities underscores the need for early screening and intervention (10, 13–15).

Gastrointestinal (GI) comorbidities, particularly inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis, also more prevalent among patients with HS (16). The mechanisms linking HS and IBD remain poorly understood, but may involve shared genetic susceptibility, dysregulated immune responses, and overlapping environmental risk factors (16). Although reported prevalences vary widely, epidemiological studies reveal a several-fold increased risk of IBD in HS patients, with some case–control studies estimating a 10-fold higher risk of Crohn’s disease (2, 6, 16).

Musculoskeletal comorbidities, especially spondyloarthritis (including ankylosing spondylitis and psoriatic arthritis), are also associated with HS (17). These inflammatory joint disorders are often underdiagnosed but can significantly impair function and quality of life. Prevalence estimates of spondyloarthritis in HS patients range from 1.5 to 40% (17), but rarely exceed 2% in the general population (18). Shared inflammatory pathways, including elevated levels of TNF-α and IL-17, may explain this overlap (17, 18).

Neuropsychiatric comorbidities are common in HS and substantially contribute to disease burden (19). The chronic pain, visible lesions, malodor, and stigma associated with HS likely contribute to the psychological distress experienced by patients. Recent studies have highlighted a possible association between HS and more severe psychiatric conditions such as schizophrenia and other psychotic disorders, potentially pointing to shared inflammatory mechanisms, including systemic cytokine dysregulation (9, 20–22). Prevalence rates of depression (15–65%) and anxiety (13–36%) in HS patients are also significantly higher than those reported in the general population (20–22).

Infectious diseases constitute another important comorbidity category in HA patients, who are at increased risk of secondary skin and soft tissue infections due to impaired barrier function, recurrent abscess formation, and colonization by pathogenic bacteria (1, 2, 9). The increased prevalence of mycoses and chronic skin infections in HS patients can potentially complicate disease management and therapeutic choices (2, 23).

A better understanding of the comorbid profile of HS is essential to improve care. While previous studies have explored individual comorbidities, few have comprehensively evaluated the full spectrum of chronic conditions in a large, unselected population. In this study, we sought to (i) estimate the prevalence of HS in a large population-based cohort in Aragón, Spain; (ii) describe the sociodemographic and clinical characteristics of affected individuals; and (iii) identify chronic comorbidities that are significantly associated with HS.

This study comprehensively analyzed the comorbidities of 1,003 patients diagnosed with HS, focusing on the most common chronic diseases and those most strongly associated with HS, irrespective of their overall frequency.

Our finding of a higher HS prevalence in women (52% increased likelihood) aligns with previous epidemiological data reporting a predominance in women, with female:male ration of approximately 3:1 (3, 27). While the reasons for this sex bias are not fully understood, exploring intrinsic and extrinsic sex-biased immunological factors, such as the microbiome and genetics, in related autoimmune conditions may offer insights into the underlying mechanisms (3, 27).

The observed HS prevalence of 0.10% in our study is lower than some global estimates, which range up to 0.40% and are often higher in clinical (1.7%) than population-based samples (0.3%) (4). This variation likely reflects differences in diagnostic criteria, study methodologies, and the populations studied, highlighting the challenges in comparing prevalence estimates across different studies (4). No significant association between HS prevalence and the percentage of women in each study has been reported to date (4).

Our observation of a lower HS prevalence among Spanish individuals compared to Sub-Saharan Africans, Latin Americans, and North Africans is consistent with previous research documenting racial and ethnic disparities in HS: previous studies have reported highest rates in African Americans (1.30%) and lower prevalence in Hispanics (0.07%) (28). The comparable rates found in Asians and Spaniards is also consistent with the relatively low prevalence reported in among Asians (28). However, variations in racial and ethnic classifications across studies complicate direct comparisons.

Consistent with previous research, our study found a higher prevalence of HS in the most deprived areas (Q4) (aOR 1.43, 95% CI 1.21–1.69), suggesting an association between lower socioeconomic status and HS (29, 30). This may be related to lifestyle factors such as diet, smoking, and access to healthcare resources (30). Current smoking status has a higher odds ratio for HS compared with controls without HS, with an OR of 4.26 (31). Approximately one-third of HS patients in our study had a documented history of smoking, which, while potentially an underestimate due to underreporting, falls within the range reported in other studies (40–92%) (31, 32).

To comprehensively understand the comorbidity profile in HS patients, we employed a two-step strategy. First, we outlined the most common comorbidities regardless of their relationship with HS. Next, we highlighted comorbidities with an increased probability of occurring in individuals diagnosed with HS. The interplay between HS and these comorbidities is complex and may involve causal, resulting, or shared etiological factors. Our study supports previous research, revealing that HS patients frequently experience multimorbidity, with almost three in four presenting with multiple diseases and symptoms of different origins.

Previous studies have shown a correlation between HS and obesity. Rates among patients with HS range from 12 to 88%, depending on the specific population studied (31, 33). A meta-analysis across Asia, Europe, and the United States involving 5,878 HS patients and over 13 million controls found that individuals with HS are four times more likely to be obese compared with the general population (pooled OR, 4.02 [2.66–6.06]) (34). In addition, obesity can exacerbate dyslipidemia. Several studies have reported a significant association between HS and lipid abnormalities, including hyperlipidemia and decreased high-density lipoprotein (HDL) cholesterol levels. The largest cross-sectional study of 3,207 HS patients and 6,412 controls found a significantly higher risk of hyperlipidemia in the HS group versus the control population (OR 1.17) (35). A case–control study also reported a significant association between HS and decreased HDL cholesterol levels in both hospital-and population-based HS patients (14).

Type 2 diabetes is a comorbidity of HS: a meta-analysis of 12 studies revealed a notably higher proportion of DM in HS cases than in non-HS healthy controls (16.1% vs. 15.7%), and a 2.17-fold higher risk of HS in patients with DM (8). The prevalence of DM in HS patients in out cohort was lower than that reported in other studies.

HS frequently impacts other vital organ systems, notably the digestive and musculoskeletal systems. While our study did not find significant associations with IBD, it is crucial to acknowledge the complex relationship between HS and conditions like Crohn’s disease and ulcerative colitis. Both HS and IBD are chronic inflammatory conditions predominantly affecting young individuals, and they are thought to share common genetic and environmental factors (16). The challenge in distinguishing between perineal manifestations of both diseases can complicate epidemiological findings. Nevertheless, numerous studies have highlighted a concurrent occurrence of HS and IBD, particularly with Crohn’s disease (36). Reported prevalence figures vary widely, ranging from 1.2 to 23%, depending on the specific populations and methodologies employed (16). For instance, two case–control studies revealed a 2.16- to 10-fold increased likelihood of IBD (encompassing both Crohn’s disease and ulcerative colitis) in individuals with HS (37). Furthermore, a separate cohort study reported a 5.6-fold elevated risk of developing IBD in patients with HS (37).

Musculoskeletal comorbidities represent a significant burden for HS patients. Inflammatory forms of arthritis, including rheumatoid arthritis, spondyloarthritis, and psoriatic arthritis, are well-documented associations. Previous research in HS patients indicates prevalences of 3.6% (OR 2.5; 95% IC 1.6–3.9) for rheumatoid arthritis, 9.1% (3.3; 2.0–5.4) for spondyloarthritis, and 4.9% (3.1; 1.8–5.3) for psoriatic arthritis (17, 18). In our cohort, we observed an association between HS and spondylosis, which may represent a broader category encompassing various forms of inflammatory arthritis, albeit with a lower observed odds ratio than reported in some prior studies (17, 18).

The association between HS and an increased risk of cardiovascular disease is a critical area of concern. Establishing a direct causal link between HS and cardiovascular conditions is challenging, primarily because HS frequently co-occurs with intermediate risk factors such as obesity and dyslipidemia, which themselves can independently alter cardiovascular risk (10, 12, 14). Hypertension, a well-established risk factor for cardiovascular diseases, is positively associated with HS. Our study population revealed a significant association between hypertension and HS, with a prevalence of 19.74% (aOR 1.26; CI 95% 1.05–1.52). However, we observed no significant association with cerebrovascular disease or acute myocardial infarction. Studies conducted in populations similar to ours have reported links between HS and comorbidities prevalent within those groups (11, 12, 38, 39). These divergent findings prompt further inquiry into whether our population exhibits distinct characteristics, or if variations in statistical adjustments might account for these differences.

Neuropsychiatric comorbidities are highly prevalent in HS patients and significantly contribute to their overall disease burden. Conditions such as depression, anxiety, and alcoholism have consistently shown a positive relationship with HS in existing literature, both in terms of occurrence and odds ratios (19–22). However, the reported prevalence rates for these conditions tend to fluctuate notably based on the study type and the specific screening methods employed. In our cohort, rates of related comorbidities including alcohol-related disorders, sexual disorders, anxiety disorders, and depression/mood disorders were slightly lower than those reported previously (21). This variability may be partially explained by the fact that our data were derived from diagnoses made by patients’ physicians, rather than from proactive screening initiatives.

Intriguingly, the neuropsychiatric comorbidity most strongly associated with HS in our study was schizophrenia and other psychotic disorders (aOR 2.17; 95% CI 1.16–4.06). This aligns with the findings of a systematic review and meta-analysis in which the likelihood of having schizophrenia was significantly higher in HS patients than control groups (OR 1.66, 95% CI: 1.53–1.79) (22). Chronic inflammation is posited as a key mechanism underlying the relationship between HS and schizophrenia, given that elevated levels of proinflammatory cytokines have been detected in HS skin lesions, as well as in the serum and cerebrospinal fluid of schizophrenia patients (22). Further supporting this connection, a large study in Finland identified a significant link between HS and schizophrenia, reporting a prevalence of 2.4% in HS patients, which is notably higher than rates observed both in psoriasis patients and the general control population (40).

Several studies have demonstrated a significant association between HS and acne vulgaris, particularly in younger patients (41, 42). Both conditions share common pathophysiological mechanisms, including follicular occlusion and neutrophilic inflammation, suggesting a shared pathogenic basis (42). The prevalence of acne among patients with HS is estimated at 15–20%, with higher rates observed in early-onset HS or syndromic phenotypes (41). In our study, acne was included under the broader coding category of “skin and subcutaneous tissue infections.” This categorization prevented us from establishing the specific prevalence of acne in HS patients. However, the overall prevalence of cutaneous infections in this group was 6.18%, indicating a significant association (aOR 3.32; 95% CI 2.56–4.30), and acne constitutes an important component of this category. This relationship is clinically important, both diagnostically and therapeutically. Azithromycin, a macrolide with anti-inflammatory properties, has shown efficacy in the treatment of acne in adolescents and may offer therapeutic benefits in HS owing to its immunomodulatory and antimicrobial effects (43). Similarly, tetracyclines such as doxycycline and minocycline, widely used in acne management, have shown clinical effectiveness in mild-to-moderate HS through their dual anti-inflammatory and antimicrobial actions (42). These therapeutic parallels underscore the importance of considering acne not only as a frequent comorbidity of HS but also as a potential avenue for shared treatment strategies.

A relationship between HS and neoplasms has been previously described. Recent studies report that patients with HS have an increased overall cancer risk and specifically an elevated risk of squamous cell carcinoma (44). In line with that study, we observed a prevalence of neoplasms of 5.88% in HS patients, but detected no significant association.

Our findings have important implications for the understanding of HS-related comorbidities, and highlight opportunities to refine HS management and improve patient well-being. Nonetheless, it should be noted that correlation does not imply causation, and thus caution is advised when interpreting these findings. While certain associations reported here align with those of earlier studies, others are novel and may necessitate further exploration to elucidate the underlying biological mechanisms.

The main strength of our research stems from the extensive, population-based approach applied, encompassing nearly all HS diagnoses within the reference area. Moreover, our comprehensive analysis of HS-related comorbidities involved a thorough examination of virtually all chronic conditions diagnosed in both primary and hospital care, and was not limited to the most prevalent or pertinent comorbidities. The utilization of Electronic Health Records (EHRs) ensured reliability of the data, which underwent continual quality control checks. However, it should be noted that clinical data were not clinically validated and were dependent on registered diagnostic codes, which may not fully represent the actual clinical status of patients. Another limitation of our study was its retrospective cross-sectional design, which inherently prevents determination of the sequential appearance of diseases, thereby impeding the establishment of cause-and-effect relationships between HS and its comorbidities. Moreover, some relevant variables (e.g., HS severity or staging, genetic information, social variables, patient-reported outcomes) were unavailable. Other variables, such as smoking status and obesity, were clearly underreported, precluding their inclusion in adjusted models. Finally, the grouping of the original diagnostic codes into Clinical Classifications Software (CCS) categories, while improving reproducibility and comparability, could potentially hamper the clinical interpretation of results due to the non-specificity of some diagnostic categories.

This large-scale, population-based study provides a comprehensive overview of the comorbidity burden associated with HS. Our findings confirm that HS is not merely a dermatologic condition, but also a systemic disease frequently associated with multiple chronic disorders across metabolic, cardiovascular, neuropsychiatric, musculoskeletal, and infectious domains. Nearly three out of four patients with HS experienced multimorbidity, highlighting the importance of early and integrated management. The strong associations identified between HS and conditions such as obesity, schizophrenia, skin infections, and white blood cell disorders emphasize the need for multidisciplinary care strategies and routine screening for comorbidities. These insights can inform clinical practice and policy by guiding risk stratification, surveillance, and resource allocation. Future longitudinal research is warranted to clarify temporal relationships and underlying mechanisms linking HS to its associated conditions.