Morningness-eveningness scale for children: Difficulties in establishing reference score intervals by age and sex throughout adolescence.

As adolescents become older, they tend to prefer sleeping and waking later due to biological maturation and social/environmental changes. Higher evening preferences relate to risks of developing physical and mental ill-health and/or academic underachievement. To identify individuals who are more vulnerable to these negative outcomes, prior studies have mostly established percentile cutoff scores in questionnaires of morningness-eveningness (M-E) preferences, a method that leads to biased estimates, and/or used linear statistical methods, which do not consider that M-E can fit other types of distribution. We reanalyzed cross-sectional data of 1815 10-18-year-old Brazilians who filled in the most popular circadian preference scale, the M-E Scale for Children (MESC). Age/sex MESC sum raw score differences were analyzed using correlations, general linear models and 44 different curve fittings based on fractional polynomials and exponential data transformation. We found a very slight correlation and general linear increase in eveningness with age, but none of the 44 tested curve fit patterns reliably explained score changes across ages, being highly variable at all ages. Hence, establishing MESC reference score intervals by age/sex is of little practical value. We discuss other factors combined with MESC scores that may help identify adolescents at risk of circadian-related problem.