Six fold Rise in LPP Incidence over 2003-2019 Period of Study
A new study from Korea set out to investigate the prevalence, incidence, and clinical characteristics of LPP in Korea. To do so, the authors used data from the National Health Insurance Service database of Korea (NHIS). The NHIS is operated by the Korean government and includes approximately 99% of the Korean population.
Only patients who had ≥3 documented visits with an International Statistical Classification of Disease, 10th revision (ICD-10) code of L66.1 (lichen planopilaris) from 2003 to 2019 were considered as LPP patients. Presumably, LPP and FFA were grouped together in this study. To include only incident cases, LPP patients with medical visits dated before 2003 were excluded. The incidence and prevalence of LPP were calculated during the 2003-2019 study period. In terms of controls, age, sex, insurance type, and income level-matched individuals without documented visits of LPP during the whole observational period were selected, to compare the comorbid conditions
RESULTS
A total of 2992 patients with LPP and 59 840 matched controls were identified. There was slight female predominance (male-to-female ratio, 1:1.24), and age with peaks in the 40–50s and teenage years. The incidence rose from around 1 per 1,000,000 in 2006 to 6 per 1,000,000 in 2019. Annual prevalence rose from around 2 per 1,000,0000 in 2006 to 11.38 per 1,000,000 in 2019. In other words, there appears to be a six fold increase in incidence or annual prevalence during this time. According to cumulative incidence data, there are now at least 5 people with LPP per 100,000 population in Korea (1 in 20,000).
Overall, data indicated that LPP incidence and annual prevalence have increased over the last 17 years. Peak incidence was observed during the summer. The incidence was 36 % higher in urban than in rural areas,
CORMORBIDITIES
The more prevalent comorbid conditions in patients at LPP diagnosis compared to controls were atopic dermatitis (odds ratio [OR], 2.06; 95% confidence interval [CI], 1.89–2.24), allergic rhinitis (OR, 1.23; 95% CI, 1.15–1.33), and asthma (OR, 1.27; 95% CI, 1.17–1.38), autoimmune connective tissue diseases (such as RA, SLE, Scleroderma, ankylosing spondylitis); OR, 1.48; 95% CI, 1.17–1.87), hypothyroidism (OR, 1.54; 95% CI, 1.30–1.83), vitamin D deficiency (OR, 3.59; 95% CI, 2.34–5.51), and rosacea (OR, 3.48; 95% CI, 1.20–10.07). These are summarized in the figure below.
