Abstract
Objectives: We aimed to determine the prevalence of cardiovascular risk factors in patients with psoriatic arthritis (PsA) followed at a large Swedish Rheumatology Clinic, and to compare differences in cardiovascular risk factors between men and women with PsA and with the general population.
Method: A questionnaire was sent to patients with PsA registered at the Rheumatology Clinic at Sahlgrenska University Hospital, Gothenburg (n = 982). Comparisons with the general population were made using data from the Swedish National Public Health Survey. Descriptive statistics are presented. Body mass index (BMI) was calculated using self-reported height and weight.
Results: Overall, 692 (70.6%) of the patients with PsA responded. The mean ± sd age was 55.6 ± 11.4 years and 52% were women. Obesity (BMI ≥ 30 kg/m2) was more prevalent (p < 0.001) in patients with PsA (28.6%) than in matched subjects from the general population (16.3%). Hypertension was also more prevalent (p < 0.001) in PsA (40.3%) than in matched subjects from the general population (24.1%), as was diabetes, with a prevalence of 10.5% in the PsA population compared with 6.2% in matched subjects (p < 0.001).
Conclusion: We found obesity to be highly overrepresented in patients with PsA compared with matched subjects from the general population. This difference was particularly seen in women with PsA. Hypertension and ever smoking were also more prevalent in women with PsA compared with matched subjects from the general population.
Patients with psoriatic arthritis (PsA) have an increased risk for cardiovascular disease (CVD) (Citation1). This has been suggested to be caused by the combination of chronic inflammation that accelerates the atherosclerotic process and an increased prevalence of cardiovascular risk factors, such as obesity, smoking, hypertension, diabetes, and hyperlipidaemia (Citation2–Citation6). A previous study showed obesity to be more frequent in PsA compared to psoriasis without arthritis and demonstrated an increasing prevalence of obesity with increasing age (Citation7). Another study showed a higher mean body mass index (BMI) in PsA compared to psoriasis, rheumatoid arthritis (RA) and the general population (Citation3), but most studies have lacked comparisons with the general population. The prevalence of overweight and obesity in Swedish patients with PsA is not known.
We aimed, first, to determine the prevalence of cardiovascular risk factors in patients with PsA followed at a large Swedish Rheumatology Clinic and compare differences in cardiovascular risk factors between men and women with PsA; and, secondly, to compare the prevalence of cardiovascular risk factors in patients with PsA, overall and by gender, with the general population.
Method
A questionnaire including self-reported weight, height, smoking habits, hypertension, diabetes (self-reported treatment), and hyperlipidaemia was sent to all patients with PsA [International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) codes L40.5, M07.2, and M07.3] aged 25–75 years and registered at the Rheumatology Clinic at Sahlgrenska University Hospital, Gothenburg (n = 982) with at least one visit to the rheumatology clinic between 1 January 2014 and 1 March 2016. In the letter sent to the patients with PsA, they were also asked whether they wanted to participate in a weight-loss study (if they had a BMI ≥ 33 kg/m2). A reminder was sent to those who did not respond to the initial questionnaire.
Comparison with the general population was made by gender and age groups, using data from the 2016 Swedish National Public Health Survey, ‘Health on Equal Terms’. The survey is sent every 2 years to 20 000 randomly selected citizens by the Public Health Agency of Sweden and is considered representative of the general population of Sweden. In 2016, the response rate was 47%. Data from ‘Health on Equal Terms’ are available from the National Board of Health and Welfare upon reasonable request.
Descriptive statistics are presented as percentages, mean and standard deviation (sd). BMI was calculated using self-reported height and weight. Independent sample t-test and chi-squared or Fischer’s exact tests were performed to compare cases with matched subjects, by gender and age groups. Logistic regression was used to calculate odds ratios. All tests were two tailed, and p < 0.05 was considered statistically significant. SPSS Statistics version 23 (IBM Corp., Armonk, NY, USA) was used for statistical analyses.
The study was approved by the Regional Ethics Committee in Gothenburg (approval number 901-15) and carried out in accordance with the Declaration of Helsinki. Informed consent was considered when replying to the questionnaire.
Results
Overall, 692 (70.6%), of the patients with PsA responded. The mean ± sd age was 55.6 ± 11.4 years and 52% (n = 360) were women. Non-responders were significantly younger (p < 0.001) and more often men (p = 0.008). The prevalence of self-reported cardiovascular risk factors in PsA patients is shown in . Obesity (BMI ≥ 30 kg/m2) was present in 198 (28.6%) of the patients with PSA and overweight (BMI 25–29.9 kg/m2) in 250 (36.1%), compared with 1231 (16.3%; p < 0.001) and 2876 (38.0%; p = 0.319), respectively, of the matched subjects from the general population. Hypertension and diabetes were reported by 279 (40.3%) and 73 (10.5%) of the PsA patients, respectively. Among the matched subjects, corresponding numbers were 1801 (24.1%; p < 0.001) and 468 (6.2%; p < 0.001).
Table 1. Characteristics of the patients (N = 692) with psoriatic arthritis, stratified by gender (332 men, 360 women).
Comparing women and men with PsA, we found that overweight was more prevalent in men. Women were more frequently current, former, and ever-smokers.
In , the study population is stratified by gender and age groups and compared with matched subjects from the health survey (n = 7559). Obesity was more prevalent in both women and men with PsA in all age groups, except for men 45–60 years of age compared with matched control subjects. In women, other risk factors for CVD, such as hypertension, diabetes (age group ≥ 45 years), and ever smoking (age group 27–60 years), were also significantly more prevalent in patients with PsA, compared with matched control subjects. In men, the only CVD risk factor that was significantly more prevalent, besides obesity, in patients with PsA was hypertension. In addition, clustering of several risk factors for CVD (variables obesity, ever smoking, hypertension, and diabetes) was significantly more prevalent in both women and men with PsA than in the general population ().
Table 2. Study population stratified by gender and age groups compared with matched subjects from the general population.
Table 3. Number of cardiovascular risk factors (variables obesity, ever smoking, hypertension, diabetes) in the study population, separated by gender and compared with matched subjects from the general population.
Discussion
We found that, of the CV risk factors, in particular obesity and hypertension were more prevalent in women and men with PsA compared with subjects from the general population, whereas diabetes and ever smoking were more prevalent only in the women with PsA. Clustering of several CV risk factors in the same individual was also more common in patients with PsA of both genders. The overrepresentation of risk factors for CVD was, however, especially marked in the women with PsA.
Obesity in PsA is associated with higher disease activity, reduced response to treatment and increased risk for CVD, especially in women with PsA (Citation1, Citation6). In addition, obesity has been shown to increase the risk for PsA in patients with psoriasis (Citation8). Obesity leads to increased mechanical loading of joints and entheses and is also characterized by constant overproduction of proinflammatory cytokines and adipokines in adipose tissue, possibly fuelling disease activity in PsA (Citation9). Leptin levels have been shown to be elevated in women with PsA, and adiponectin, which has been suggested to have proinflammatory properties in joints, was higher in PsA patients than in psoriasis without arthritis (Citation10).
In line with our findings, observational studies from Belgium, North America, and Ireland have shown high prevalences of obesity and metabolic syndrome in patients with PsA (Citation4–Citation6). A study by Bhole et al included subjects from the general population for comparisons and showed that obesity was more prevalent in PsA than in RA and in the general population (Citation3). Bhole et al found the mean BMI in PsA patients to be 2.3 kg/m2 higher than in the RA population. This was reported to be consistent with a US registry study (Citation11)
Obesity was reported by 28.6% of our PsA population, which is lower than the 45% reported by Labitigan et al, despite similar age and gender distributions (Citation5). This discrepancy could possibly be explained by the fact that obesity is more prevalent in the populations in Belgium, North America, and Ireland than in Sweden (Citation12).
Conflicting results exist regarding smoking and the risk for PsA (Citation8). In our study, 51% were ever-smokers. Previous studies found around 40% of patients with PsA to be ever-smokers (Citation3, Citation13). These differences could be attributed to younger study populations and the lower proportion of women in other studies.
As a limitation to the present study, self-reported data may lack validity. Self-reported weight is often underestimated and height may be overestimated. A review study found the underestimation of weight to be especially pronounced in women (Citation14). Assessing or validating the investigated variables at a hospital visit could have increased the reliability of the collected data.
We identified cases using ICD-10 codes, which can cause diagnostic misclassification. Although we did not validate the diagnostic codes for PsA in our centre, a previous validation study showed a generally high validity in the Swedish outpatient register for many diagnoses (Citation15).
Another limitation is that the cases were not derived from the same population as the controls to which they are being compared. Cases were identified from tertiary care, which may have led to more ill cases, whereas controls are from the general population. This may hamper comparisons. There may also be economic as well as geographic mismatching, since the reference population is a national representation. The underrepresentation of young men with PsA answering the questionnaire is also a limitation, possibly affecting the generalizability of the results.
It is imperative to identify cardiovascular risk factors and obesity in people with PsA, since those with PsA have increased cardiovascular morbidity and mortality, and obesity can lead to increased disease activity and reduced response to pharmacological treatment.
Conclusion
We found obesity and hypertension to be highly overrepresented in patients with PsA, compared with matched subjects from the general population. This difference was particularly seen in women with PsA. Other risk factors for CVD, such as diabetes and ever smoking, were also more prevalent in women with PsA compared with matched subjects from the general population.
Acknowledgements
This work was supported by grants from the Swedish state under the agreement between the Swedish Government and the county councils, the ALF-agreement (ALFGBG-825511), the Health and Medical Care Executive Board of the Västra Götaland, the Gothenburg Society of Medicine, Inger Bendix Foundation for Medical Research, Rune and Ulla Amlövs Foundation for Rheumatology Research, the Swedish Psoriasis Association, and the Swedish Rheumatology Association research grant in collaboration with Roche.
Disclosure statement
No potential conflict of interest was reported by the authors.
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