Even with recent pharmacologic treatment advances, narrowband UVB (NB-UVB) phototherapy remains a versatile, safe, and efficacious adjunctive or exclusive treatment for multiple dermatologic conditions, including psoriasis and atopic dermatitis. 1-9 Some providers choose NB-UVB phototherapy as a first-line treatment for older adult patients who frequently use multiple treatment modalities for more than 1 health condition. Older adults with atopic dermatitis and psoriasis are at higher risk for comorbidities such as autoimmune disorders, diabetes mellitus, dyslipidemia, sleep disorders, neuropsychiatric disorders, and cardiovascular disease that can complicate treatment compared with their peers without these dermatologic diagnoses. 10-12 Polypharmacy (ie, the use of 5 or more daily medications), frequently associated with these conditions, contributes to prescribers pursuing NB-UVB phototherapy as a nonpharmacologic treatment, but some providers wonder if it is as effective and safe for their older patients compared with younger patients.
In a prior study, Matthews et al13 reported that 96% (50/52) of patients older than 65 years achieved medium to high levels of clearance with NB-UVB phototherapy. Nonetheless, 2 other findings in this study related to the number of treatments required to achieve clearance (ie, clearance rates) and erythema rates prompted further investigation. The first finding was higher-than-expected clearance rates. Older adults had a clearance rate with a mean of 33 treatments compared to prior studies featuring mean clearance rates of 20 to 28 treatments.7,8,14-16 This finding resembled a study in the United Kingdom17 with a median clearance rate in older adults of 30 treatments. In contrast, the median clearance rate from a study in Turkey18 was 42 treatments in older adults. We hypothesized that more photosensitizing medications used in older vs younger adults prompted more dose adjustments with NB-UVB phototherapy to avoid burning (ie, erythema) at baseline and throughout the treatment course. These dose adjustments may have increased the overall clearance rates. If true, we predicted that younger adults treated with the same protocol would have cleared more quickly, either because of age-related differences or because they likely had fewer comorbidities and therefore fewer medications.
The second finding from Matthews et al13 that warranted further investigation was a higher erythema rate compared to the older adult study from the United Kingdom.17 We hypothesized that potentially greater use of photosensitizing medications in the United States could explain the higher erythema rates. Although medication-induced photosensitivity is less likely with NB-UVB phototherapy than with UVA, certain medications can cause UVB photosensitivity, including thiazides, quinidine, calcium channel antagonists, phenothiazines, and nonsteroidal anti-inflammatory drugs.8,19,20 Therefore, photosensitizing medication use either at baseline or during a course of NB-UVB phototherapy could increase the risk for erythema. Age-related skin changes also have been considered as a potential cause for erythema. One study found that the skin of older patients was more sensitive than younger patients, resulting in a lower minimal erythema dose (MED)14—the lowest UV dose that results in erythema.21 Others, however, found similar MEDs across age groups, but older adults experienced more intense erythema in the late phase of NB-UVB treatment.22,23 Such conflicting findings indicate that questions remain regarding the risk for erythema in older patients and if photosensitizing medications are responsible for an increased risk.
This retrospective study aimed to determine if NB-UVB phototherapy is equally effective in both older and younger adults treated with the same protocol; to examine the association between the use of photosensitizing medications and clearance rates in both older and younger adults; and to examine the association between the use of photosensitizing medications and erythema rates in older vs younger adults.
Methods
Study Design and Patients—This retrospective cohort study used billing records to identify patients who received NB-UVB phototherapy at 3 different clinical sites within a large US health care system in Washington (Group Health Cooperative, now Kaiser Permanente Washington), serving more than 600,000 patients between January 1, 2012, and December 31, 2016. The institutional review board of Kaiser Permanente Washington Health Research Institute approved this study (IRB 1498087-4). Younger adults were classified as those 64 years or younger and older adults as those 65 years and older at the start of their phototherapy regimen. A power analysis determined that the optimal sample size for this study was 250 patients.
Individuals were excluded if they had fewer than 6 phototherapy treatments; a diagnosis of vitiligo, photosensitivity dermatitis, morphea, or pityriasis rubra pilaris; and/or treatment of the hands or feet only.
Phototherapy Protocol—Using a 48-lamp NB-UVB unit, trained phototherapy nurses provided all treatments following standardized treatment protocols13 based on previously published phototherapy guidelines.24 Nurses determined each patient’s disease clearance level using a 3-point clearance scale (high, medium, low).13 Each patient’s starting dose was determined based on the estimated MED for their skin phototype. If the patient was using photosensitizing medications, the protocol indicated a need for a decreased starting dose—down 25% to 50%—depending on the presumed level of photosensitivity. All clinical sites used the same protocol, but decisions about adjustments within this range were made by individual registered nurses and dermatologists, which could lead to variability across sites. Protocols also directed nurses to query patients about specific treatment responses, including erythema, tenderness, or itching; how their condition was responding; use of photosensitizing medications; missed treatments; and placement of shielding. Doses were adjusted accordingly.