RESEARCH LETTER

Serum 25-hydroxyvitamin D status in individuals with psoriasisin the general population

Patrick Benjamin Wilson

Received: 3 April 2013 / Accepted: 21 May 2013

� Springer Science+Business Media New York 2013

Abstract There is a dearth of data assessing serum

25-hydroxyvitamin D (25[OH]D) status in psoriasis. This

population-based study in the United States evaluated

25(OH)D status in psoriasis and examined the associations

between 25(OH)D and psoriasis severity. The 2003–2006

National Health and Nutrition Examination Survey was

analyzed. Participants aged 20–59 years self-reported

psoriasis, psoriasis body surface area (BSA), and psoriasis

life impairment (PLI). Serum 25(OH)D was assessed with

the DiaSorin radioimmunoassay. General linear models

were used to examine the associations between psoriasis

and 25(OH)D while accounting for age, gender, race/eth-

nicity, season, and body mass index (BMI). Among the

5,841 participants with complete data, 148 reported a

psoriasis diagnosis. Mean 25(OH)D levels and deficiency

prevalences (\20 and \30 ng/mL) were not different

between those with and without psoriasis. Among those

with psoriasis, a multivariate model showed participants

with BSA [10 hand palms trended towards lower

25(OH)D compared to those with minimal BSA (-4.98

ng/mL, P = 0.07). PLI was not associated with 25(OH)D,

but BMI showed an inverse association with 25(OH)D

(coefficient = -0.40, P \ 0.001). In summary, dermatol-

ogists may consider measures of adiposity as better

screening tools for vitamin D deficiency than BSA

involvement among psoriatics with mild-to-moderate

disease.

Keywords Vitamin D � Epidemiology � Psoriasis �Public health

Introduction

Deficiency of serum 25-hydroxyvitamin D (25[OH]D) is a

serious problem associated with numerous auto-immune

conditions [1, 2] and pre-mature mortality [3]. Studies have

found low 25(OH)D is common among individuals with

psoriasis [4, 5]. Both studies, however, recruited individ-

uals from hospitals, which represent only a subset of

patients. The National Health and Nutrition Examination

Survey (NHANES) uses complex sampling to achieve a

representative sample of the American population [6]. For

2003–2006, information on psoriasis and 25(OH)D was

collected. This investigation evaluated 25(OH)D status in

psoriasis and examined the associations between 25(OH)D

and psoriasis severity.

Materials and methods

This was a cross-sectional analysis of NHANES data.

NHANES stratified, multistage probability sampling pro-

cedure uses four stages (counties, segments, households,

individuals). Individuals within households are drawn at

random within designated age–sex–race/ethnicity screen-

ing subdomains. To assess psoriasis, participants aged

20–59 self-reported whether they had ever been told by a

healthcare provider they had psoriasis [6]. Participants

reporting psoriasis rated body surface area (BSA) from 1 to

4 based on the following question: ‘‘Do you currently have

little or no psoriasis (\1 hand palm), only a few patches

(1–2 hand palms), scattered patches (3–10 hand palms), or

P. B. Wilson (&)

School of Kinesiology, University of Minnesota, 220 Cooke

Hall, 1900 University Avenue SE, Minneapolis,

MN 55455, USA

e-mail: wilso733@umn.edu

123

Endocrine

DOI 10.1007/s12020-013-9989-8

extensive psoriasis ([10 hand palms)?’’ Psoriasis life

impairment (PLI) was rated from 1 to 10 with the following

question: ‘‘On a scale of 1–10, how much of a problem has

psoriasis been in your life, where 1 means no problem and

10 means a very large problem?’’ [6]. NHANES did not

assess psoriasis type.

Serum 25(OH)D was collected via venous blood sample.

Centrifugation separated serum after samples were kept at

room temperature for 1 h. Serum samples were subsequently

frozen (-20 �C) for shipment to the National Center for

Environmental Health, where they were analyzed with the

DiaSorin radioimmunoassay (Stillwater, Minnesota). The

co-efficient of variation ranged from 4.4 to 13.2 %, and

sensitivity was B1.5 ng/mL. NHANES files with adjusted

25(OH)D values were used since quality investigations

showed mean 25(OH)D varied from year-to-year because of

assay reformulation and lot variation. Assessments were

completed during the summer for northern states and winter

for southern states. Cutoff values of 30 and 20 ng/mL were

selected given the debate over optimal levels [7]. Consent

was obtained using protocols approved by the National

Center for Health Statistics Ethics Review Board.

PLI scores were transformed into quartiles (low counts

for some values). Proportions were compared using the

Rao–Scott likelihood Chi square test. SPSS Complex

Samples (version 20) general linear model was used to

examine psoriasis diagnosis as a predictor of 25(OH)D

while accounting for age, gender, race/ethnicity, season

(November–April vs. May–October), and body mass index

(BMI). Among psoriatics, Spearman correlations examined

the associations between BSA, PLI, and 25(OH)D. Two

additional multivariate models examined BSA and PLI as

predictors of 25(OH)D among psoriatics. These models

used minimal BSA and the lowest quartile of PLI as ref-

erence groups and accounted for age, gender, race/ethnic-

ity, season, BMI, and prescription vitamin D analog use.

Results

The 2003–2006 NHANES screened 25,623 individuals,

and 20,470 agreed to participate. After excluding individ-

uals with missing data on psoriasis status, 25(OH)D, and

BMI, 5,841 participants were analyzed. There were 5,693

participants without psoriasis and 148 reporting psoriasis.

No differences in age, smoking, or the proportion of men/

women were apparent between those with and without

psoriasis. Participants with psoriasis, however, were more

likely to be obese (45 vs. 33 %, P \ 0.01), non-Hispanic

white (83 vs. 69 %, P \ 0.01), and have greater than a high

school education (68 vs. 60 %, P = 0.03).

Mean 25(OH)D was 24.2 ng/mL (95 % confidence

interval [CI] 22.8–25.7) and 23.6 ng/mL (95 % CI

22.8–24.5) for participants with and without psoriasis

(P = 0.37). Mean 25(OH)D was 21.3 ng/mL (95 % CI

20.2–22.4) during winter and 25.3 ng/mL during summer

(95 % CI 24.3–26.2), with no significant differences by

psoriasis status. The prevalence of 25(OH)D \30 ng/mL

was 72.5 and 76.4 % for participants with and without

psoriasis (P = 0.29). The prevalence of 25(OH)D\20 ng/

mL was 33.0 and 34.9 % for participants with and without

psoriasis (P = 0.67). In the general linear model including

age, gender, race/ethnicity, season, and BMI, participants

with psoriasis had a non-significant 0.26 ng/mL greater

25(OH)D (P = 0.71).

Table 1 shows mean 25(OH)D among individuals with

psoriasis by BSA and PLI. The Spearman correlations

demonstrated that BSA (q = -0.15, P = 0.07) and PLI

(q = -0.10, P = 0.24) were weakly, non-significantly

correlated with 25(OH)D. In the multivariate model

including BSA, participants with BSA equal to 1–2 and

3–10 hand palms did not have significantly lower 25(OH)D

compared to those with minimal BSA (\1 hand palm).

Those with [10 hand palms trended toward having lower

25(OH)D (-4.98 ng/mL, P = 0.07). In the multivariate

model including PLI, no significant differences in

25(OH)D were present between PLI categories. BMI

showed an association with 25(OH)D in both models

(coefficient = -0.40, P \ 0.001). Only four participants

with psoriasis used vitamin D analogs, which were not

significantly associated with 25(OH)D.

Discussion

Using a population-based sample, vitamin D deficiency

was not more common in psoriasis. Gisondi et al. [4] found

that 57.8 % of psoriasis patients had 25(OH)D\20 ng/mL,

Table 1 Mean serum 25(OH)D by psoriasis severity measures

among 148 participants with psoriasis

Mean (95 % CI)

Body surface area involvement

\1 hand palm (N = 81) 25.0 (22.9–27.1)

1–2 hand palms (N = 40) 23.4 (20.0–26.9)

3–10 hand palms (N = 20) 25.5 (21.6–29.3)

[10 hand palms (N = 7) 17.5 (13.9–21.0)

Psoriasis life impairment

Quartile 1 (N = 40) 25.6 (23.0–28.1)

Quartile 2 (N = 29) 26.2 (22.2–30.2)

Quartile 3 (N = 45) 23.2 (20.4–26.0)

Quartile 4 (N = 34) 22.1 (18.7–25.6)

25(OH)D 25-hydroxyvitamin D, CI confidence interval, N represents

the number of participants within each category

Endocrine

123

compared to 29.7 % of controls. Likewise, Orgaz-Molina

et al. [5] found that the prevalence of 25(OH)D\30 ng/mL

was 79.1 % among psoriasis patients, compared to 58.1 %

of controls. Caution is warranted when comparing results

because 25(OH)D deficiency prevalence can vary with

numerous factors, including race, dietary vitamin D intake,

and ultraviolet light exposure [8, 9]. While the previous

studies had well-defined controls, this study had the

advantage of a nationally representative population, which

has implications for population-wide 25(OH)D screening.

BSA and PLI were not significantly associated with

25(OH)D. The majority of participants had mild disease,

but nonetheless, those reporting a BSA of 1–10 hand palms

did not have lower 25(OH)D compared to those with

minimal BSA. Psoriatics reporting BSA [10 hand palms

had lower 25(OH)D, but inferences are limited by the small

number of participants. In support of these findings, neither

of the previous investigations found an association between

25(OH)D and the Psoriasis Area and Severity Index [4, 5].

BMI was negatively associated with 25(OH)D in this

study, as it was in Orgaz-Molina et al. [5]. Adipose tissue

sequesters vitamin D after its synthesis, which provides a

causal mechanism for the association between BMI and

25(OH)D [10].

In summary, dermatologists may consider measures of

adiposity as better screening tools for vitamin D deficiency

than BSA involvement among psoriatics with mild-to-

moderate disease (\10 hand palms).

Acknowledgments NHANES is a major program of the National

Center for Health Statistics, which is part of the Centers for Disease

Control and Prevention. No funding was used to conduct this analysis

or write this manuscript.

Conflict of interest The author declares that he has no conflict of

interest.

References

1. M.F. Holick, T.C. Chen, Vitamin D deficiency: a worldwide

problem with health consequences. Am. J. Clin. Nutr. 87, 1080S–

1086S (2008)

2. M. Rotondi, L. Chiovato, Vitamin D deficiency in patients with

Graves’ disease: probably something more than a casual associ-

ation. Endocrine 43, 3–5 (2013)

3. T. Skaaby, L.L. Husemoen, C. Pisinger, T. Jørgensen, B.H.

Thuesen, Fenger et al., Vitamin D status and incident cardio-

vascular disease and all-cause mortality: a general population

study. Endocrine 43, 618–625 (2013)

4. P. Gisondi, M. Rossini, A. Di Cesare, L. Idolazzi, S. Farina, G.

Beltrami et al., Vitamin D status in patients with chronic plaque

psoriasis. Br. J. Dermatol. 166, 505–510 (2012)

5. J. Orgaz-Molina, A. Buendı́a-Eisman, M.A. Arrabal-Polo, J.C.

Ruiz, S. Arias-Santiago, Deficiency of serum concentration of

25-hydroxyvitamin D in psoriatic patients: a case–control study.

J. Am. Acad. Dermatol. 67, 931–938 (2012)

6. NHANES 2003-2004 Questionnaire Data. National Health and

Nutrition Examination Survey. http://www.cdc.gov/nchs/nhanes/

nhanes2003-2004/DEQ_C.htm. Accessed 6 May 2013

7. A.C. Ross, J.E. Manson, S.A. Abrams, J.F. Aloia, P.M. Brannon,

S.K. Clinton et al., The 2011 report on dietary reference intakes

for calcium and vitamin D from the Institute of Medicine: what

clinicians need to know. J. Clin. Endocrinol. Metab. 96, 53–58

(2011)

8. K.A. Bertrand, E. Giovannucci, Y. Liu, S. Malspeis, A.H. Eli-

assen, K. Wu et al., Determinants of plasma 25-hydroxyvitamin

D and development of prediction models in three US cohorts. Br.

J. Nutr. 108, 1889–1896 (2012)

9. J.H. Langdahl, L.L. Schierbeck, U.C. Bang, J.E. Jensen, Changes

in serum 25-hydroxyvitamin D and cholecalciferol after one

whole-body exposure in a commercial tanning bed: a randomized

study. Endocrine 42, 430–435 (2012)

10. J. Wortsman, L.Y. Matsuoka, T.C. Chen, Z. Lu, M.F. Holick,

Decreased bioavailability of vitamin D in obesity. Am. J. Clin.

Nutr. 72, 690–693 (2000)

Endocrine

123