Natural history of naevi: a two‐wave study

Abstract

Summary Background Naevi number changes with age. Thus, a better understanding of naevus biology will shed more light on the genetic and environmental factors involved in melanoma development. Objectives To use a two‐wave study to better understand the evolution of naevi in healthy adults. Methods This study is a prospective two‐wave study based on adult twins from the TwinsUK registry (n = 414) who underwent total body naevus counts with an interval of at least 15 years. A negative binomial hierarchical model with two levels, the individual and the twin pair, was used to estimate expected changes in naevus count between the first and second visit, at any specific body site and on the whole body. The model was adjusted for age, calendar year at the first visit, height and skin type. Results The mean age of participants was 46 years at the first visit and 63 years at the second visit (the mean elapsed time between visits was 17 years). An increase in naevus count was observed in 235 (57%) participants and a decrease was observed in 166 (40%). The mean difference in total naevus count between the two visits was nine. The expected total body naevus count increased, on a logarithmic scale, by 0·28 [95% confidence interval (CI) 0·16–0·40] with a change in the incidence rate of total body naevus count of 32% (95% CI 17–49%). However, the observed increase in naevus count over time was observed only on the upper parts of the body, whereas there was no evidence of an increase on the lower parts. Conclusions Naevus counts increased slightly over time at older ages, but this was dependent on body site. The overall decrease in naevus counts previously reported in cross‐sectional studies has not been confirmed by this longitudinal study.

A different finding on whether naevus numbers change during adulthood

“…In this issue of the BJD , Ribero et al 6 . explore this phenomenon using a longitudinal study design, in which 414 female adult twins in the UK had total‐body naevus counts at least 2 mm in diameter measured 15 years apart (mean age 46 and 63 years, respectively).…”

“…Surprisingly, a systematic review 8 identified only two previous longitudinal studies of adults in the general population, both of which were very small and reported limited data. Thus, the paper by Ribero et al 6 addresses a major gap in our knowledge of the natural history of common melanocytic naevi. Based on their findings, it appears that results from previous cross-sectional studies may reflect a cohort effect rather than a true age effect.…”

“…In this issue of the BJD, Ribero et al 6 explore this phenomenon using a longitudinal study design, in which 414 female adult twins in the UK had total-body naevus counts at least 2 mm in diameter measured 15 years apart (mean age 46 and 63 years, respectively). Contrary to the findings of previous cross-sectional studies, they instead found a mean 32% increase in naevi between the two visits, after adjusting for age and calendar year at the first visit, height and skin type.…”

“…Interestingly, this increase in naevi over time was observed only on the upper parts of the body and not on the lower parts, leading the authors to postulate that misclassification with solar lentigines and flat seborrhoeic keratosis might explain the increase on the upper body. Interrater reliability of naevus counts is generally good, 7 and this was optimized by Ribero et al 6 using the same protocol and having the naevus counts performed by research nurses trained by the same dermatologist. Surprisingly, a systematic review 8 identified only two previous longitudinal studies of adults in the general population, both of which were very small and reported limited data.…”

“…Surprisingly, a systematic review 8 identified only two previous longitudinal studies of adults in the general population, both of which were very small and reported limited data. Thus, the paper by Ribero et al 6 . addresses a major gap in our knowledge of the natural history of common melanocytic naevi.…”