Of the 60,000 households surveyed, 42,249 (70%) responded, yielding a weighted total of 116,202 individuals. The distribution of sociodemographic characteristics for the total TNS panel and for the responding households is displayed in Table 1 .
A total of 19,889 individuals (17.1% of the total population) experienced at least one of the following four symptoms associated with eczematous conditions: itching/scratching, red or inflamed rash, excessive dryness/scaling, and thickening of skin. This is the "symptomatic" subpopulation, but because of its nonspecific makeup, we established the more selective empirical criteria as defined above under "Methods." Based on empirical criteria, eczema was identified in 12,424 individuals (10.7% of the total weighted population, 58% of the symptomatic subpopulation), and AD was identified in 6,931 individuals (6% of the total weighted population, 32.3% of the symptomatic subpopulation) (Figure 1). The overall prevalence of empirical eczema and empirical AD was relatively consistent and showed no linear trend among different-sized population centers. However, when analyzed by income level, the prevalence decreased with increasing household income, from 14% for empirical eczema and 8% for empirical AD at an income of less than $15,000 (US), to 9% and 5%, respectively, at an income of ≥ $75,000 (US). Among Asians and Pacific Islanders and among Native Americans, the prevalences of empirical eczema (13%) and empirical AD (8%) were notably higher than in other populations (10-11% and 6%, respectively), but these differences were not statistically significant.
Prevalence and sociodemographic variation according to eczematous condition (empirical diagnosis).
Self-Reported Physician Diagnosis
A total of 7,952 individuals (6.8% of the total population, 37.1% of the symptomatic subpopulation) reported a physician diagnosis of an eczematous condition (eczema, seborrheic dermatitis, contact dermatitis, or AD). The pattern of self-reported diagnosis was relatively consistent and showed no linear trend, regardless of household income (range, 6.4-7.4%), but increased slightly with increasing size of the population center (6.3-7.2%). The percentage of such diagnoses was notably higher among Asians and Pacific Islanders (9.7%), Native Americans (8.5%), and black/African Americans (7.7%), as compared with white persons (6.7%), but these differences were not statistically significant.
Characterization According to Symptoms and Comorbidities
Questionnaire data that characterized symptoms and symptom locations in the subpopulations with empirical eczema and empirical AD revealed that itching/scratching (a criterion for diagnosis) was experienced by all individuals. Other symptoms experienced most frequently in both subpopulations were excessive dryness/scaling and red or inflamed rash ( Table 2 ). Most individuals (74%) with empirical eczema experienced two to three symptoms whereas 61% of individuals with empirical AD experienced two to three symptoms. The locations cited by at least 40% of individuals with each diagnosis were arms or hands, legs or feet, and head, face, or scalp (see Table 2 ). Twenty-eight percent of those with empirically defined eczema reported three or more symptom locations, compared with 34% of those with empirically defined AD.
Age at the onset of symptoms varied notably between the subpopulation with empirical AD and the subpopulation with empirical eczema (Figure 2). The most frequent ages at onset for empirically defined eczema were in the range of 18 to 29 years (20%) although onset also occurred frequently in the age range of 5 years or less (17%). For empirically defined AD, onset occurred most frequently in the age range of 5 years or less (28%). In general, with increasing age there was a steady decline in the percentage of individuals experiencing an onset of symptoms.
Age (in years) at onset of skin symptoms among individuals with empirical eczema (n = 12,424) or empirical atopic dermatitis (AD) (n = 6,931).
Severity and Impact of Eczematous Conditions
For many individuals, eczema and AD are chronic and unremitting, their symptoms experienced daily (23% and 28%, respectively) ( Table 3 ). Twenty-seven percent of individuals with empirical eczema and 10% of individuals with empirical AD experienced short-term symptoms (≤ 14 days per year), and most (50% and 62%, respectively) experienced limited or intermittent symptoms (15-364 days per year). Symptoms were severe in 14% of individuals with empirical eczema and 18% of individuals with empirical AD and mild in 37% and 30%, respectively. Sleep disturbance occurred frequently in 7% and 10% of individuals with eczema and AD, respectively ( Table 4 ).
Comorbidities related to the skin (self-reported physician diagnoses) were generally reported at similar rates in the subpopulation with empirical eczema and in the subpopulation with empirical AD ( Table 5 ). Approximately half of the individuals in each subpopulation reported a diagnosis of an eczematous condition (see Table 5 ). In contrast, the rates of asthma (33%) and hay fever/allergic rhinitis (30%) in the subpopulation with empirical AD were at least 50% higher than the corresponding rates in the subpopulation with empirical eczema (20% for each diagnosis).
Self-Reported Physician Diagnosis versus Nonphysician Diagnosis
The severity of symptoms and the frequency of sleep disturbance were compared among members of the symptomatic subpopulation with and without a self-reported physician diagnosis of an eczematous condition (ie, seborrheic dermatitis, AD, contact dermatitis, or eczema), and the results are shown in Table 6 . For each eczematous condition, the results of those with a physician diagnosis and those without a physician diagnosis were similar. As would be expected, those in the physician-diagnosed group were more severely impaired (p < .001) and more likely to experience sleep disturbance related to their symptoms (p < .001). All symptoms were reported more often among diagnosed individuals than among undiagnosed individuals (p < .001). However, key eczematous symptoms were quite common in the undiagnosed group (itching/scratching, 76%; excessive dryness/scaling, 56%; red or inflamed rash, 44%). These results, along with the finding that only 37.1% of the symptomatic subpopulation reported a physician diagnosis of eczema, indicate that there is a high prevalence of undiagnosed eczema that may be comparable in severity and impact to eczema that is diagnosed by a physician. This suggests that there is a high level of undertreatment of eczematous conditions and/or considerable self-treatment with over-the-counter products in the United States.
Dermatitis. 2007;18(2):82-91. © 2007 American Contact Dermatitis Society
Cite this: A Population-Based Survey of Eczema Prevalence in the United States - Medscape - Jun 01, 2007.