Introduction

Psoriasis is an inflammatory disease typically characterized by formation of erythema, plaques, and scaling of the skin. Proinflammatory cytokines including TNF-α, IL-23, or IL-17 are upregulated in psoriatic lesions and promote keratinocyte proliferation and inflammation in the skin [1, 2]. These proinflammatory cytokines also promote systemic inflammation, which is associated with a range of comorbidity including increased cardiovascular risk [3]. This includes risk factors such as hyperlipidemia, hypertension, type 2 diabetes mellitus, obesity [4], and metabolic syndrome [5], affecting around 40% of psoriasis patients, compared to 13–27% of the general population [6, 7]. Psoriasis patients are at increased risk of metabolic syndrome, which may be related to an increase in circulating adipocytokines [5, 8], mediating systemic proinflammatory effects [9].

The metabolic and cardiovascular comorbidity of psoriasis, such as obesity, is characterized by inflammatory processes, such as adipose tissue inflammation in obesity and insulin resistance or vascular inflammation in coronary artery disease [10,11,12,13,14]. A cycle of feedback between psoriasis and obesity is postulated, in which psoriasis causes systemic inflammation that in turn stimulates adipocytes to secrete proinflammatory cytokines that can promote cutaneous inflammation (Fig. 1) [15]. Obesity and metabolic syndrome negatively impact psoriasis disease severity, treatment response, and also aggravate the cardiovascular risk in psoriasis patients [9, 16,17,18,19]. Increased cutaneous inflammation is associated with vascular inflammation in psoriasis patients, which increases with psoriasis severity [20, 21].

Fig. 1
figure 1

Interaction of skin and adipose tissue in psoriasis and concomitant obesity. Psoriasis causes systemic inflammation that in turn stimulates visceral fat tissue to secrete proinflammatory cytokines that can promote cutaneous inflammation. TNF-alpha tumor necrosis factor alpha, IL interleukin

Full size image

A recent survey (PsoHealth) indicated that around 40% of German psoriasis patients are overweight, with an additional 30% classified as obese [2]. According to the World Health Organization (WHO) 2008, overweight is considered as BMI ≥ 25 kg/m2, whereas obesity is considered as BMI ≥ 30 kg/m2. To assess the relationship between psoriasis, obesity, patient behavior, and approach of care providers to weight management in individuals with psoriasis in the general population, a survey on health, nutrition, and physical activity was designed and conducted in German participants with self-reported psoriasis (hereafter referred to as participants) (Umfrage zu ERnährung und Aktivität bei PSOriasis-Patienten, or ERAPSO).

Methods

Study Objectives

The study aim was to collect representative cross-sectional data from approximately 10,000 participants (comprising around 0.5% of individuals with psoriasis in Germany) about eating behavior, physical activity, prevalence of obesity and other factors contributing to metabolic syndrome, as well as the extent to which care providers offered support with weight management. The data was then used to assess the association between psoriasis, obesity, and patient behavior. A second aim was to give insight into current treatment practices and identify the potential need for intervention.

Survey Execution and Analysis

ERAPSO was conducted with IT support from Clariness GmbH, Hamburg, Germany. The survey was online from 29 January to 21 March 2018. Completing the survey took approximately 10 min. ERAPSO was promoted in German language on German websites, search engines, and social media, targeting individuals with psoriasis and encouraging their participation by asking for help in developing a better understanding of psoriasis.

According to the European consensus on definition of psoriasis severity, mild psoriasis is defined as BSA ≤ 10% and moderate to severe disease is defined as BSA > 10% [22]. In this survey, BSA was self-assessed and entered online. To aid self-assessment of BSA, participants were shown a small graphic of a palm stating that the area of one palm is equal to 1.0% of the body surface.

For subgroup analyses, participants were divided into one group consisting of participants with mild disease (self-reported BSA ≤ 10%) and another group consisting of participants with moderate to severe disease (self-reported BSA > 10%). Participants reported data on (1) elevated cholesterol levels or other dyslipidemias, (2) impaired fasting glucose and/or diabetes mellitus, (3) arterial hypertension, and (4) waist circumference.

As a result of its observational and cross-sectional nature, the data restricted itself to purely descriptive methodology, and no statistical testing was performed. Furthermore, as a result of this survey’s self-reporting design, answers could not be confirmed.

Compliance with Ethics Guidelines

Ethics committee approval was not required because ERAPSO was conducted as an online survey. All the participants received explanations about the survey details. Informed consent was obtained from all participants for data storage, processing, and publication. This survey was performed in accordance with the Helsinki Declaration of 1964 and its later amendments.

Results

Demographic Data

Overall, 15,693 individuals participated in this survey (Fig. 2). Of those, 97.0% (n = 15,226) currently lived in Germany, and were included in the study. The study population comprised the 65.3% of the participants living in Germany who stated that they had been diagnosed with psoriasis (n = 9940, “true completers”), the 32.3% of participants who had never been diagnosed with psoriasis (n = 4923), and 2.4% who were not sure (n = 363), and were therefore excluded from the analysis. All of the following results describe only participants living in Germany with a confirmed diagnosis of psoriasis (n = 9940).

Fig. 2
figure 2

Flow chart of ERAPSO survey participants

Full size image

Within the study population, 55.1% (n = 5477) were female and 44.9% (n = 4463) were male, with a mean age at survey completion of 51.3 ± 14.0 years (Table 1). A majority (65.1%; n = 6474) were currently being treated for psoriasis by their dermatologist and 14.5% (n = 1439) were being treated by other physicians, for example general practitioners. A minority of participants (3.7%; n = 368) consulted a homeopath or alternative practitioner (multiple selections were possible). Nearly one-quarter of participants (25.3%; n = 2518) stated that they did not receive any treatment for psoriasis at all.

Table 1 Baseline characteristics
Full size table

Psoriasis Severity

In this survey, the mean BSA affected by psoriasis was 12.7 ± 19.1% (Table 1). The majority of participants (74.5%; n = 7404) had mild disease while 25.5% (n = 2536) were affected by moderate to severe psoriasis. Participants with mild psoriasis had a mean self-reported BSA of 4.0 ± 2.9% while participants with moderate to severe psoriasis had a mean self-reported BSA of 38.0 ± 23.5%. This is consistent with established prevalence of moderate to severe psoriasis.

Obesity

Mean participant body weight was 83.8 ± 21.2 kg. Mean BMI was 28.5 ± 14.1 kg/m2 (Table 1). Figure 3 shows the distribution of BMI in the overall study population. In this population, 66.9% (n = 6647) of all participants with psoriasis were overweight or obese (defined by the WHO 2008 as BMI ≥ 25 kg/m2). In comparison, approximately 50–60% of the general German population is overweight or obese [23]. Most participants (90.2%) with BMI ≥ 25 kg/m2 perceived themselves as being overweight. Figure 4 shows the association of BMI with psoriasis severity. Participants with high BMI tended to show increased reported BSA.

Fig. 3
figure 3

BMI distribution shows high burden of obesity in German participants. 66.9% of German participants are overweight or obese (BMI ≥ 25 kg/m2). In comparison, approximately 50–60% of the total German population is overweight or obese [23]. Total N = 9940. BMI body mass index

Full size image
Fig. 4
figure 4

Affected body surface area increases with BMI in ERAPSO participants. BMI subgroups are shown with associated mean affected body surface area. Total N = 9940, n = number of participants per BMI subgroup. BMI body mass index

Full size image

Cardiovascular Profile

Within the study population, 5.9% (n = 582) had reported coronary heart disease, 2.5% (n = 246) reported angina pectoris, 3.3% (n = 331) had signs of myocardial infarction, and 2.5% (n = 251) reported having had a stroke. On division by BMI subgroups, higher BMI was associated with increased prevalence of cardiovascular risk factors (CVRFs) and of cardiovascular events (CVEs) (Figs. S1 and S2, electronic supplementary material).

Of all the participants (n = 9940), 23.1% (n = 2297) reported high cholesterol or other dyslipidemias. Impaired fasting glucose was reported by 9.0% (n = 894) of participants and 9.5% (n = 940) had been diagnosed with diabetes mellitus. In total 34.4% (n = 3422) were diagnosed with arterial hypertension. Mean waist circumference in women was 88.4 + 16.5 cm and that in men was 92.7 + 17.0 cm. More women had elevated waist circumference (n = 3961/5477 [72.3%] above 78.7 cm) than men (n = 855/4463 [19.2%] above 100.0 cm). These are common cutoff values for elevated waist circumference [24].

Diet and Physical Activity

Among overweight participants, 12.6% (n = 836) were currently on a weight loss diet. The majority of overweight participants had tried weight loss diets already (60.7%, n = 4038) and 55.6% (n = 2244) had been successful (completed to participants’ satisfaction) with weight loss diets at least once.

Food was said to influence psoriasis severity by 25.9% (n = 1914) of participants with mild psoriasis and 31.0% (n = 785) of participants with moderate to severe psoriasis. Participants who stated that food can have positive or negative effects on their disease severity were asked to evaluate different types of food and how it affects their disease (Fig. 5). While vegetables, fish, potatoes, pasta, rice, and dairy products were perceived to have positive effects on psoriasis severity in many participants, convenience products, fast food, sweets, and alcohol appeared to have negative effects on psoriasis severity in approximately 50% of participants in the overall population. Within the ERAPSO population, 9.0% (n = 346) of participants with mild psoriasis say that psoriasis has prevented them from losing weight by diet, whereas 20.3% (n = 257) of participants with moderate to severe psoriasis say that their psoriasis has prevented them from losing weight by diet.

Fig. 5
figure 5

Positive and negative effects of different types of food on psoriasis. All data shown are the percentage of participants. Participants (n = 2699 [27.2%] of the total population) stated that food can have positive or negative effects on their disease severity. They were asked to evaluate different types of food and how it affects their disease. Darker color shades represent a higher percentage

Full size image

Only 21.2% (n = 1408) of overweight participants reported currently exercising to lose weight. Participants who were overweight reported greater discomfort with physical activity than those with BMI < 25 kg/m2 (Fig. 6a) when their psoriasis is active. One-quarter (25.6%; n = 904) of participants with mild psoriasis and 46.6% (n = 514) of participants with moderate to severe psoriasis said that psoriasis has prevented them from exercising at least once. Figure 6b illustrates how active psoriasis is associated with discomfort with physical activities in participants with increasing disease severity, to the extent of causing total abandonment of physical activity. Eighteen percent of participants with mild psoriasis and 25.8% of participants with moderate to severe psoriasis said that exercise can influence their disease severity. These participants were asked to evaluate different types of physical activity and how they affected their disease severity (Fig. 7). While walking, cycling, and endurance sports showed positive effects in 41.0%, 32.4%, and 26.6% of participants, respectively, housework showed a negative impact on psoriasis severity in 31.1% of participants.

Fig. 6
figure 6

Active psoriasis impairs physical exercise especially in overweight participants (a) and participants with moderate to severe psoriasis (b). All data shown are the percentage of participants. Participants were asked how active psoriasis disease affects their physical activities. The figure shows the percentage of participants suffering from impairment of physical activities. Impairment of sportive activities was examined in a population doing sports with varying intensity. a Illustrates impairment of physical activities in participants with normal weight (BMI < 25 kg/m2) compared to overweight participants (BMI ≥ 25 kg/m2). b Reports the same outcomes dependent on mild psoriasis (BSA ≤ 10%) or moderate to severe psoriasis (BSA > 10%). Darker color shades represent a higher percentage. BMI body mass index, BSA body surface area

Full size image
Fig. 7
figure 7

Different types of physical exercise can have positive and negative effects on psoriasis. All data shown are the percentage of participants. Participants (n = 1989 [20.0%] of the total population) stated that physical activity can have positive or negative effects on their disease severity. They were asked to evaluate different types of physical activities and how they affected their disease. Darker color shades represent a higher percentage

Full size image

Nearly one-third (35.7%; n = 2374) of overweight participants have been approached by their treating physician to lose weight by going on a diet or exercising. Only 13.3% (n = 887) of overweight participants stated that their physicians and health insurances offer specific programs to lose weight using diets or physical activity.

Discussion

ERAPSO identified a higher prevalence of overweight and obesity among participants than in the general German population, where around 50–60% are overweight or obese [23]. Rates of overweight and obesity in participants matched those determined in PsoHealth [2]. There is not only an objective burden of obesity but also a subjectively perceived burden of obesity, as participants show intact self-perception regarding overweight/obesity. Despite this, only a minority of overweight participants are currently attempting to lose weight by diet or exercise. This underlines the need for professional external support in multiple approaches.

Awareness of obesity or the necessity to treat obesity in psoriasis patients appears relatively low among physicians, as only a minority of participants were offered weight loss programs. Awareness of the negative impact of obesity and metabolic syndrome on psoriasis disease severity needs to be raised, and the efficacy of treatment options established. For example, weight loss combined with cyclosporine therapy improves psoriasis more than cyclosporine alone [25]. The combined efficacy of weight loss and secukinumab treatment for plaque psoriasis is under current investigation (METABOLYX trial, NCT03440736).

Compared to ERAPSO findings on the prevalence of CVRFs in participants, in Germany 28.1% of men and 27.1% of women overall have dyslipidemia, with a significant increase in prevalence with increasing age and with no significant differences between sexes [26]. Prevalence of arterial hypertension is around 40–50% in adults in Germany (Robert Koch Institut, Statistisches Bundesamt 2018). Type 2 diabetes occurs in 7–8% of the general German population (Deutsche Diabetes Gesellschaft 2018). ERAPSO participants showed a similar prevalence of dyslipidemia, arterial hypertension, and diabetes mellitus to the general German population. Increasing prevalence of CVRFs with growing BMI translated into increased incidence of CVEs.

Participants with moderate to severe psoriasis perceived stronger positive and negative influences of food and sports on their disease than participants with mild psoriasis. Psoriasis severity was identified by participants as a limiting factor for engaging in exercise, as might be expected given physical symptoms and concerns regarding outer appearance in sports clothing. Interestingly, some participants reported that severity of psoriasis also impacted their capacity to follow a specific diet. This suggests an intersection between the psychological effects of psoriasis, including depression and, potentially, emotional eating, and obesity, and may warrant further research. In addition, treating psoriasis and adequate control of skin symptoms could help participants to lose weight since psoriasis severity is associated with impairment in diets and exercise. Participants reported “healthy” foods such as vegetables having a positive effect on their psoriasis, whereas processed food, sweets, and alcohol were more frequently labelled as having negative effects. A perceptual effect cannot be ruled out, as for instance it is unclear whether increased alcohol consumption in psoriasis participants is a risk factor for the disease [27]. However, when giving advice on nutrition and diets for psoriasis patients, physicians can continue to recommend “healthy” food like fiber-rich vegetables and fish, which seems to have positive effects on participants’ perception of disease. In addition, when giving advice on physical exercise, physicians can continue to recommend daily physical activities like endurance sports, cycling, or walking. Furthermore, endurance sports, cycling, or walking are often more practical than resistance training to include as daily activities and they have a higher chance to burn body fat compared to resistance training. ERAPSO revealed participants’ perceptions of weight loss treatment as being limited. In terms of weight management, diet, and exercise, treatment offerings appeared to be insufficient.

Limitations of ERAPSO include the self-selecting patient population. For example, severely depressed participants may be less likely to complete online surveys. A further limitation is that all data collected, including psoriasis diagnosis, were based on participants self-reporting of their health information, not on physician’s records. Finally, differences in digital literacy between participants compared with the general population might be a further source of bias, with the ERAPSO participants being a self-selecting digitally literate subpopulation.

Conclusions

ERAPSO showed a high prevalence of overweight and obesity among participants in Germany, with psoriasis severity being associated with BMI. A relationship between obesity and CV risk factors or events was also apparent. Only a minority of overweight/obese participants were currently on a diet or exercising to lose weight, and few were approached by their physician with weight loss recommendations, indicating a lack of professional weight loss support for psoriasis patients. Psoriasis severity was associated with impairment in participation and success of diets and physical activity; therefore, optimal psoriasis disease control could in itself be a means to facilitate patients’ weight loss attempts. ERAPSO shows an unmet medical need in obese individuals with self-reported psoriasis, with insufficient offerings for professional support to lose weight or increase physical activity.