Sleep
Sleep is a fundamental component of overall health and well-being. The Sleep Measure in the Giji Holistic Index evaluates 6 indicators of Sleep Quality and Sleep Hygiene, which are essential for maintaining cognitive function, emotional regulation, and physical health.
This measure utilizes scientifically-supported indicators, such as sleep duration, consistency, and the absence of sleep disturbances, to provide an objective evaluation of how effectively respondents manage their sleep. By identifying areas where improvements can be made, the Sleep Measure aims to offer actionable insights for enhancing life satisfaction through better sleep practices.
Sleep Duration
During sleep the body undergoes multiple recovery processes including muscle repair, immune function restoration, and cognitive restoration. Sleep deprivation or inconsistent sleep can impair these processes.
Both excessive and inadequate sleep has been shown to be associated with poor health. A systematic meta-analysis conducted by Cappuccio and colleagues (2011) showed that short sleepers (commonly <7h per night, often <5h per night) and long sleepers (commonly >8h or 9h per night) have a 12% and a 30% greater risk of dying, respectively, than those sleeping 7 to 8h per night.
However, studies suggest the optimal amount of sleep may vary from person to person. For example, Lajunen and colleagues (2023) found sleep duration is positively associated with subjective wellbeing in most populations except Japan, where short sleep and high subjective wellbeing is common. The National Sleep Foundation conservatively recommends 7-9 hours. Ultimately, you are the best judge of whether your body is getting the adequate duration of sleep.
Daytime Wakefulness
Daytime alertness is a well-established marker of proper sleep quality and duration. Those who experience sufficient and uninterrupted sleep are more likely to feel energetic throughout the day. The Centers for Disease Control and Prevention (CDC) identifies chronic fatigue and daytime sleepiness as key symptoms of poor sleep hygiene, which can be linked to conditions like sleep apnea or insomnia.
Two accessible and well-known assessments for sleep conditions include the STOPBANG checklist and the Epworth Sleepiness Scale. The former includes one question "Do you often feel Tired, Fatigued, or Sleepy during the daytime (such as falling asleep during driving or talking to someone)?" while the latter lists a number of daytime scenarios when someone might drift off to sleep and asks you to rate your likelihood (such as after lunch, or while watching a movie).
More generally, afternoon slumps, or naps throughout the day, are associated but not necessarily indicative of low wakefulness and poor sleep outcomes.
Sleep-based Mood Impairment
Mood regulation is strongly affected by sleep quality. Indeed the relationship is so strong that a study conducted by Ryerson University found that 87% of those who relieved insomnia through therapy also resolved their depression.
Poor sleep outcomes will often express themselves as increased emotional volatility, including mood swings, irritability, and heightened stress responses. These may all be present even in the absence of other indicators such as daytime drowsiness.
Sleep is of course not the only thing that can cause mood swings, however it is one of the most likely.
Sleep Latency
Sleep onset latency, or the time it takes to fall asleep, should ideally be 15-30 minutes for healthy sleep. This indicator mainly aims to capture the incidence of difficulty falling asleep among respondents - associated with either insomnia or poor sleep hygiene. For the person with either of these, improving awareness and education on the process and importance of sleep may greatly assist in relieving these factors. Cognitive Behavioural Therapy is by far the most effective treatment for insomnia, even more so than prescribed medicines.
Interestingly, a low sleep onset period of less than 15 minutes may be a symptom of narcolepsy or hypersomnia. However this should be accompanied by a host of other sleep-related symptoms before a diagnosis is made. There would not be a cause for concern if, for example, you typically fall asleep within five minutes but do not experience daytime sleepiness.
Sleep Disturbance
Sleep disturbance refers to the act of waking in the night and struggling to return to sleep. Sleep disturbance, and the resulting fragmented sleep, is linearly associated with risk of inflammatory disease and all-cause mortality. In plain words, as a person's sleep becomes more disturbed their likelihood of dying in any given moment also increases. Sleep disturbance is closely associated with rumination on arousing topics, such as a recent cancer diagnosis (see Davidson et al 2002).
This indicator takes a 'less is better' scoring approach in acknowledgement both that occasional sleep disturbances are unavoidable, and that the research has not determined a 'safe limit' on the sliding scale.
Sleep Consistency
Consistent sleep schedules are crucial for maintaining circadian rhythm, the body’s internal clock. Studies from the Sleep Research Society show that fluctuations in sleep timing greater than 90 minutes can lead to circadian misalignment, which negatively affects sleep quality, mood, and overall health. Regularity in sleep and wake times -yes, even on weekends- supports better long-term sleep outcomes.
Sleep consistency is used by the Index as a proxy for good sleep hygiene, which broadly consists of:
Exercise 20 to 30 minutes a day but no later than a few hours before going to bed.
Avoid caffeine, nicotine and alcohol late in the day.
Relax before bed – try a warm bath, reading, or another relaxing routine.
Avoid bright lights and loud sounds,
Keep the room at a comfortable temperature
Don’t watch TV or have a computer in your bedroom.
Don’t lie in bed awake. If you can’t get to sleep, do something else, like reading or listening to music, until you feel tired.
