Can you write an abstract based on the paper below?:

To the editor: Melasma is an acquired, often symmetric, facial dyschromia characterized by light-brown to dark-brown macules to patches on the forehead, malar cheeks, upper lip, and chin.1 Genetic predisposition, pregnancy, chronic UV exposure, and hormonal therapy have all been implicated in its etiology.1 Although studies have reported a prevalence between 8.8-41%, its epidemiology in the general population, however, has not been clearly elucidated.1,2

We aimed to understand how demographic factors correlate with melasma prevalence using the All of Us open-access database initiative from the National Institutes of Health in the United States.3 

A cross-sectional statistical analysis of the All of Us database was performed. Patients with melasma were identified using a diagnostic search using ICD-10 code L81.1, with their electronic medical record data analyzed based on sex, age group, and self-identified race. The Wald method with 95% confidence intervals (CI) was used to calculate melasma prevalence in each population subset. 

The All of Us database has 407,333 patients currently enrolled, with 744 identified melasma cases, indicating an overall 0.18% prevalence (95% CI, 0.17-0.20) (Table 1). A 19:1 female-to-male prevalence was noted, with a mean of 95.3% women and 4.7% men. The average age at the time of enrollment was 55.1 years (standard deviation 12.9). A positively skewed bell-shaped curve was observed for the age groups with the highest prevalence (0.37% [95% CI, 0.30-0.44]) in the 46-50 age group (Figure 1). Although there were no statistically significant differences between age groups 41-45, 46-50, and 51-55 years, the prevalence data from these 3 age groups was significantly different from the rest of the patient population. The prevalence of melasma in Hispanic (0.36% [95% CI, 0.32-0.40]) and Asian (0.37% [95% CI, 0.28-0.48]) patients was 3-times that of White (0.12% [95% CI, 0.09-0.11]) and Black (0.12% [95% CI, 0.09-0.14]) patient populations. 

Our analysis has multiple limitations. Given that the database analyzed is categorized by billing codes, it is highly likely that many cases of melasma were either not coded or coded as other forms of hyperpigmentation or dyschromia, thereby suppressing the true prevalence of this disorder and leading to far lower prevalence rates than prior studies. The All of Us database is also 55.2% White, 19.0% Black, 18.1% Hispanic, and 3.5% Asian, contrasting with the racial demographics of the 2022 US Census (75.8% white, 13.6% Black/African American, 18.9% Hispanic/Latino, and 6.1% Asian).4 These inherent differences may contribute to sample bias within the database in underrepresented (White and Asian) and overrepresented (Black) patient populations, leading to underestimation and overestimation of melasma prevelance rates, respectively.

Overall, analysis of the All of Us patient database reveals that Asian and Hispanic race and a 41-55 year age group are correlated with a significantly greater prevalence of melasma. Further epidemiological study using a larger patient pool from a database not dependent on billing codes would expand on these findings.