Iltatyyppit

Iltatyyppit, or evening types, is a term used in chronobiology to describe individuals whose circadian preference leans toward later bedtimes and wake times and whose peak alertness and performance tend to occur in the evening. The concept sits at the evening end of the circadian typology spectrum, with morning types (aamutyypit) on the opposite end and many people occupying an intermediate position. Iltatyyppit are typically characterized by later sleep onset, longer time in bed to achieve sufficient sleep, and greater difficulty waking up for early obligations when schedules require early rising.

Assessment and prevalence: Eveningness is commonly measured with instruments such as the Morningness-Eveningness Questionnaire (MEQ) or the Munich Chronotype Questionnaire (MCTQ). The distribution of evening types varies across age and culture; eveningness tends to be more common in adolescence and young adulthood and often declines with age as schedules and biology align more with early waking.

Health and performance implications: Evening types may experience more social jetlag, a mismatch between biological timing and social obligations, which can contribute to sleep debt and daytime sleepiness. Some associations have been reported with mood variation, substance use, and academic or work performance when schedules do not accommodate an individual’s chronotype. However, causality is complex and influenced by environmental and behavioral factors.

Practical considerations: For iltatyyppit who must follow early schedules, strategies include consistent sleep-wake times, morning light exposure, and reducing evening light and stimulating activities before bedtime. Flexible scheduling and alignment of activities with individual chronotypes can mitigate sleep disruption and support well-being.

See also: chronotype, circadian rhythm, morningness-eveningness.