Title of the study: Sleep and subjective age: Protect your sleep if you want to feel young
Authors: Leonie JT Balter & John Axelsson
Contact: leonie.balter@su.se
Abstract: The current studies examined the impact of insufficient sleep and sleepiness on the subjective experience of age. Study 1, a cross-sectional study of 429 participants (282 females (66%), 144 males, 3 other; age range 18-70) showed that for each additional day of insufficient sleep in the last 30 days, subjective age increased by 0.23 years. Study 2, an experimental crossover sleep restriction study (N = 186; 102 females (55%); 84 males; age range 18-46) showed that two nights of sleep restriction (4h in bed/night) made people feel 4.44 years older compared to sleep saturation (9h in bed/night). Additionally, moving from feeling extremely alert (KSS score of 1) to feeling extremely sleepy (KSS score of 9) was associated with feeling 10 years older in both studies. These findings provide compelling support for insufficient sleep and sleepiness to exert a substantial influence on how old we feel, and that safeguarding sleep is likely a key factor in feeling young.

Code version: RMarkdown
Overview files:
2 studies:

1. Study 1 Lifespan study (“lifespan.xlsx”)
2. Study 2 Experimental sleep restriction study (“bs.xlsx” and “agegender.xlsx”)

R Markdown html link: Sleep-and-subjective-age-Script.html

Description of the data and file structure

Study 1

The lifespan.xlsx file contains a column with:

• Participant id (“id_new”)
• Calendar age (“age”)
• Subjective age (“feelage”)
• Gender ("gender"), answer option: "Female", "Male", or Other, please specify:
• Text entry if gender is "Other, please specify:" (“genderspecify”)
• Karolinska Sleepiness Scale rating (“sleepy”, range 1-9)
• Number of days with insufficient sleep in the past 30 days (“insuffsleep”, range 0-30)
• rMEQ item 1 ("rmeq_getupownchoice"), answer option: 05:00 - 6:30 AM; 6:31 - 7:45 AM; 7:46 - 9:45 AM; 9:45 - 11:00 AM; 11:00 - 12 (noon); After 12 (noon)
• rMEQ item 2 ("rmeq_tiredwokenup"), answer option: Very tired; Fairly tired; Fairly refreshed; Very refreshed
• rMEQ item 3 ("rmeq_timetired"), answer option: 8:00 PM - 9:00 PM (20:00 - 21:00); 9:01 PM - 10:15 PM (21:01 - 22:15); 10:16 PM - 12:45 AM (22:16 - 00:45); 12:46 AM - 2:00 AM (00:46 - 2:00); 2:01 AM - 3:00 AM (2:01 - 3:00)
• rMEQ item 4 ("rmeq_feelingbestpeak"), answer option: 5:00 AM - 8:00 AM (5:00 - 8:00); 8:01 AM - 10:00 AM 8:01 - 10:00); 10:01 AM - 5:00 PM (10:01 - 17:00); 5:01 PM - 10:00 PM (17:01 - 22:00); 10:01 PM - 4:59 AM (22:01 - 4:59)
• rMEQ item 5 ("rmeq_chronotype"), answer option: Definitely a "morning" type; Rather more a "morning" than an "evening" type; Rather more an "evening" than a "morning" type; Definitely an "evening" type

Study 2

The bs.xlsx file contains a column with:

• Participant id (“id”)
• Subjective age (“feelage”)
• Karolinska Sleepiness Scale rating (“sleepy”, range 1-9)
• rMEQ item 1 ("rmeq_getupownchoice"), answer option: time entry
• rMEQ item 2 ("rmeq_tiredwokenup"), answer option: Very tired; Fairly tired; Fairly refreshed; Very refreshed
• rMEQ item 3 ("rmeq_timetired"), answer option: time entry
• rMEQ item 4 ("rmeq_feelingbestpeak"), answer option: time entry
• rMEQ item 5 ("rmeq_chronotype"), answer options: Definitely a "morning" type; Rather more a "morning" than an "evening" type; Rather more an "evening" than a "morning" type; Definitely an "evening" type

The agegender.xlsx file contains a column with:

• Participant id (“id”)
• Gender ("gender"), answer option: female (F), male (M) or other (Other, please specify:)
• Calendar age (“age”)

Code/Software

R Markdown file shows script and results
The following packages were used:
ggplot2, writexl, readxl, dplyr, lme4, sjPlot, tidyr, patchwork, knitr, reshape2, ggdist