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Module 1.5b

Young Adults
REM sleep increases Figure 1.5-7
Awake as night progresses
The stages in a typical
REM night’s sleep
People pass through a
Stage 1 multistage sleep cycle several
times each night. As the night
Stage 2 goes on, periods of deep sleep
diminish and, for younger
adults, REM sleep increases.
Stage 3
As people age, sleep becomes
more fragile, with awakenings
1 2 3 4 5 6 7 8 being more common among
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
Hours of sleep older adults ( Kamel & Gammack,
2006 ; Neubauer, 1999 ).
Older Adults
Awake
Copyright © Bedford, Freeman & Worth Publishers.
REM
®
AP Exam Tip
Stage 1
Stage 2 Study this cycle of sleep care-
fully. One common mistake that
students make is to believe that
Stage 3
REM sleep comes directly after
deep Stage 3 sleep. As you can
1 2 3 4 5 6 7 8 see, it does not. Generally, Stage 2
Hours of sleep follows Stage 3; then comes REM.
This clarification will help for the
®
AP exam.

during REM sleep. Neuroscientists have also identified brain regions that are active during
dreaming, which enables them to detect when dreaming occurs ( Siclari et al., 2017 ).

What Affects Our Sleep Patterns?

1.5-6 How do biology and environment interact in our sleep patterns?
1.5-6 How do biology and envir onment interact in our sleep patter ns?
True or false? “Everyone needs 8 hours of sleep.” False. Newborns often sleep two-thirds of
their day, most adults no more than one-third (with some thriving on fewer than 6 hours AP Science Practice
®
nightly, while others slumber 9 or more hours). But there is more to our sleep differences Research
than age. Some people are awake between nightly sleep periods — sometimes called “first
sleep” and “second sleep” ( Randall, 2012 ). And some find that a 15-minute midday nap is Having a huge sample size, such as
1.3 million people, allows research-
as effective as another hour of nighttime sleep ( Horne, 2011 ). ers to easily generalize their findings
Sleep patterns are genetically influenced ( Hayashi et al., 2015 ; Mackenzie et al., 2015 ). to the intended population —
One analysis of 1.3 million people identified 956 genes related to sleep patterns such as in this case, all people.
insomnia ( Jansen et al., 2019 ). Another identified genes associated with being a morning
person ( Jones et al., 2019 ).
Sleep patterns are also culturally, socially, and economically influenced. In Britain, CULTURAL
Canada, Germany, Japan, and the United States, adults average 7 hours of sleep on work- AWARENESS
days and 7 to 8 hours on other days ( NSF, 2013 ). Earlier school start times, more extra- While the function and purpose of
curricular activities, and fewer parent-set bedtimes lead American adolescents to get less sleep (which we will discuss later in
sleep than their Australian counterparts ( Short et al., 2013 ). Stress, including the experience this unit) transcend culture, you can
of discrimination or poverty, can also disturb sleep ( Johnson et al., 2018 ; Mai et al., 2019 ; see here that our beliefs and values
about sleep are heavily influenced by
Vancampfort et al., 2018 ; Yip et al., 2020 ). our culture.

Sleep: Sleep Stages and Theories Module 1.5b 97

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