Atopic Dermatitis Associated With Lymphopenia and Lower Mean Lymphocyte Counts

Adult patients with atopic dermatitis have an increased rate of lymphopenia and common infections, although lymphocyte counts are not predictive of increased infection risk, according to a study in the Journal of the European Academy of Dermatology and Venereology.

Investigators used patient data from the UK Clinical Practice Research Datalink (CPRD GOLD) to compare the odds of lymphopenia in patients with atopic dermatitis with a matched cohort without atopic dermatitis. The analysis was repeated with US data from the National Health and Nutrition Examination Survey (NHANES).

Participants were adults (aged ≥18 years) who were registered with a CPRD practice between April 1, 1997, and March 31, 2015, and were eligible for Hospital Episode Statistics linkage. Each patient with atopic dermatitis was randomly matched with up to 5 individuals by age (within 15 years), sex, and general practice.

Lymphopenia was defined as documentation of testing revealing 2 low lymphocyte counts (<1×10⁹/L) within 3 months. Logistic regression was used to compare the odds of lymphopenia in patients with atopic dermatitis with that in individuals without the condition.

A total of 71,731 adults with atopic dermatitis (median age, 68 years; 66% women) and 126,349 adults without the condition (median age, 70 years; 65% women) were included in the primary analysis. Median follow-up was 9.0 years in those with atopic dermatitis vs 8.8 years in those without the condition. Among participants with atopic dermatitis, 4.1% (2909) had lymphopenia compared with 3.7% (4700) without the condition. The investigators also reported that the prevalence of lymphopenia increased with atopic dermatitis severity.

The adjusted odds ratio (OR) for lymphopenia in individuals with vs without atopic dermatitis was 1.16 (95% CI, 1.09-1.23) and increased with greater atopic dermatitis severity (OR for severe atopic dermatitis, 1.89; 95% CI, 1.54-2.32). Use of immunosuppressive drugs also was associated with lymphopenia (OR, 1.15; 95% CI, 1.06-1.24).

Analysis of lymphocyte count involved 1,497,306 measurements from 286,906 patients with atopic dermatitis and 4,035,870 measurements from 866,319 matched individuals without the condition. Patients with atopic dermatitis had lower lymphocyte counts compared with individuals without the condition (adjusted mean difference -0.047×10⁹/L; 95% CI, 0.051-0.043), with a greater difference occurring in men and older individuals. A decrease in lymphocyte count was associated with greater atopic dermatitis severity. Use of immunosuppressive drugs did not appear to influence the association between atopic dermatitis and lymphopenia.

Study authors estimated adjusted hazard ratios (HR) by comparing the following common infection rates in patients with atopic dermatitis with individuals without atopic dermatitis: cellulitis, 1.58 (95% CI, 1.57-1.60); varicella zoster, 1.11 (95% CI, 1.06-1.16); gastroenteritis, 1.33 (95% CI, 1.31-1.34); and urinary tract infection, 1.18 (95% CI, 1.17-1.19). Estimated HRs for these 4 infections were unchanged after additional adjustment for time with lymphopenia.

The NHANES analysis included data from 22,624 participants between 1999 and 2006. Of this group, 5563 participants were part of the 2005-2006 survey, of whom 7% to 8% had atopic dermatitis within the previous year. Pooled analysis for 1999 to 2006 showed a trend toward an inverse association between atopic dermatitis within the past year and lymphocyte count (adjusted mean difference, -0.03; 95% CI, -0.07 to 0.02), as well as a trend toward an increased odds of lymphopenia (adjusted OR, 1.30; 95% CI, 0.80-2.11).

As study limitations, the researchers noted that many individuals with lymphopenia may not undergo testing or have primary care records available and that an increased rate of infections could have caused lower lymphocyte counts in patients with atopic dermatitis rather than the condition itself. In addition, time with lymphopenia accounted for a small proportion of follow-up time, which resulted in a lack of power, and atopic dermatitis severity levels were based on therapeutic prescriptions rather than by direct measure of severity.

“Knowing that individuals with atopic eczema have higher rates of infection can help in the development of a more comprehensive approach to decrease morbidity in individuals with atopic eczema and may help guide more targeted vaccination and/or treatment strategies in the future,” stated the investigators.

Disclosure: One of the study authors declared an affiliation with a biotechnology company. Please see the original reference for a full list of authors’ disclosures.

This article originally appeared on Dermatology Advisor