Sleep and Exercise

Question 1

Who needs sleep?

Answer 1

Sleep predicts mortality!
Review of studies conducted with 1.3 million people (Francesco et al., 2010)
Results:
“Short sleepers” (less than 7 hours/night and especially less than 5 hours/night) have 12% greater risk of mortality
“Long sleepers” (more than 8-9 hours/night) have 30% greater risk of mortality (depressed and sick people tend to sleep a lot - this is tricky because it may be confounded by the health factors

Short and long sleep associated with elevated BMI and mortality

• plotting hours of sleep against mortality and BMI
• seem to be tracking together- lowest mortality if you’re getting 7 hours of sleep

Question 2

Sleep and disease

Answer 2

Too much sleep and too little sleep are associated with:

• Cardiovascular morbidity and mortality
• Hypertension
• Obesity
• Type 2 diabetes
• Colds
• Depression
• Cognitive impairment

Question 3

Sleep and colds

Answer 3

Participants reported sleep duration and sleep efficiency (how much of the time you are actually lying down in bed is spent ACTUALLY sleeping) for 14 days prior to viral challenge
Longer sleep associated with lower risk of developing a cold
Effects significant for age, BMI, SES, personality, stress, depression, positive affect, health behaviors
-possible pathways - sleep is over an above these other pathways

Question 4

Are young adults susceptible to effects of poor sleep?

Answer 4

In sample of 17,465 college students:

• 63% slept 7-8 hours
• 21% were short sleepers
• 16% were long sleepers

Short sleepers reported poorer health

• Association remained significant controlling for sex, age, smoking status, physical activity, alcohol, parental education, BMI, country of origin
• could be that they aren’t sleeping enough because they’re in poorer health but could also be the sleep itself

Shorter sleep associated with higher blood pressure in adolescents
long sleep associated with lowest BP

Question 5

Sleep and depression

Answer 5

sleep and depression go hand in hand
-sleep dimension predicts getting depressed again?

those with no sleep disturbance in year 1 had very low chance of getting depression in year 2
In older adults, persistent sleep disturbance predicted persistent or recurrent depression at year 2 (much higher likelihood of getting depressed in the following year)

Question 6

Sleep and cognition

Answer 6

A single night of sleep deprivation compromises the neural and behavioral capacity for committing new experiences to memory
No sleep = poor learning/memory
Inadequate sleep also interferes with social and emotional function

Question 7

Sleep and inflammation

Answer 7

There is a bi-directional interaction between sleep and inflammation
-Induction of proinflammatory cytokines leads to changes in sleep (sickness behavior pathway)
-Sleep disruption leads to increases in inflammation (health behavior pathway)
This has consequences for inflammation-associated conditions

Question 8

Models of sleep disruption

Answer 8

Experimental sleep deprivation studies

• Bring people into sleep lab and monitor them while they sleep
• After you let them adapt to environment, disrupt their sleep and measure physiological changes

Question 9

Partial sleep deprivation

Answer 9

12 day sleep study (Vgontzas et al., 2004)
-Nights 1-4: 8 hours of sleep
-Nights 5-12: 6 hours of sleep (woken two hours early)
Looked at effects on inflammation
-Elevations in IL-6 after sleep deprivation period
draw blood samples every hour
-IL-6 levels higher, particularly in the evening
-sleep deprivation increases IL-6

Napping helps reduce this effect
No nap group: Elevated IL-6 after sleep deprivation
Nap group: Lower IL-6 during nap

Partial sleep deprivation (Irwin et al., 2006)
5 nights in sleep lab - one night sleep deprivation
-Night 1: adaptation
-Nights 2-4: baseline (sleep 11pm – 7am)
-Night 5: sleep deprivation (wake up at 3am)

Just a few hours of sleep deprivation lead to increases in cytokine gene expression and elevated production of proinflammatory cytokines
-3-fold increase in gene expression from just ONE NIGHT!!!

Is this why we feel depressed, tired, irritable, and have trouble concentrating after a bad night of sleep??
your brain may be telling you that your sick - one hypothesis

Question 10

Exercise and health

Answer 10

Exercise has well-known beneficial effects on physical health (CVD, cancer, etc.)
Research also shows beneficial effects of exercise on mental health
-Decreased rates of major depression and anxiety disorders
-Less depression, anger, and stress
-Increased self-esteem, social support, & positive affect

But…
-Could it just be that people who are depressed or stressed don’t want to exercise? Or don’t have time? (maybe not causal - just an association)
Let’s test the exercise –> mental health link experimentally (get people to exercise and see if it affects mood)
Can test causality through interventions
If we get people to exercise, does their mood change?

Question 11

Soccer intervention study

Answer 11

N=104 young sedentary but healthy men (age 18 – 40)
Randomly assigned to one of three conditions:
1) Soccer/cognitive behavioral therapy (CBT) condition
(2) Individual exercise Condition
(3) No treatment control condition

Methods:
10 week intervention, 2 sessions per week
Answered surveys throughout the intervention
Dependent variables/ outcomes:
-Depressive symptoms
-Quality of social relationships

Soccer/ CBT treatment condition
During practices, the soccer coach used CBT techniques to address weekly themes such as:
Relaxation
Teamwork and communication
Identifying personal strengths
Goal setting
Problem solving

Intervention effects on depressive symptoms:
Depressive symptoms decreased over time in both treatment groups compared to controls
No difference between individual exercise and soccer/ CBT condition
Benefits remained two months later

Question 12

Magnitude of effect?

Answer 12

Intervention studies have tested causality and found that exercise improves mental health

How big are the effects?
Review of effect sizes:
Effect size = Measure of the strength of relationship between two variables
Cohen’s d is one type of effect size statistic
.2 = small .5 = medium .8 = large
Helps us interpret the actual “significance” or meaning of the result not just statistical significant

Question 13

How effective is exercise in improving mental health?

Answer 13

In meta-analyses:

• Cohen’s d for exercise interventions on depression, d=.72 (Craft & Landers, 1998)
• Cohen’s d for exercise interventions on anxiety, d=.36 (Long & Stavel, 2008)

Question 14

What psychological mechanisms might explain why exercise is associated with lower depressive symptoms?

Answer 14

Increased positive mood
Increased self-esteem
Increased social support
Interruption of negative thoughts (can interrupt rumination)

Question 15

Mechanisms (Y)

Answer 15

Physiological
Endogenous opioids (endorphins)
Decrease in inflammation

Question 16

Mechanisms: Endorphins

Answer 16

Endorphins(“endogenous morphine”) are natural pain killers your body produces that are secreted during exercise, excitement, pain, consumption of spicy food, love, and orgasms.
Reduces pain and creates a sense of overall well-being
Produced in pituitary gland and hypothalamus
Secreted when contracting muscles

Question 17

Depression and inflammation

Answer 17

In epidemiological studies, inflammation (i.e. CRP, IL-6) has been found to positively correlated with depressive symptoms and episodes of major depression

Experimental studies have shown that inducing inflammation leads to “sickness” behavior including increased depressive symptoms

Question 18

Exercise and inflammation

Answer 18

Cross-sectional studies suggest that those who exercise have lower levels of chronic inflammation

Inflammatory profiles of exercisers:

• Physically active people have low levels of circulating IL-6 and CRP than sedentary people (this is baseline state - not acute effects of exercise)
• Training for a marathon reduces circulating pro-inflammatory cytokines

Question 19

How might exercise lead to lower levels of inflammation?

Answer 19

Two ways that this can happen:
Adipose tissue (fat) secretes pro-inflammatory cytokines
if you Lose weight you will have less adipose tissue so you should have lower levels of pro inflammatory cytokines

when you have a lot of fat cells the cells get necrotic (they start dying)
-in obese tissue the macrophages come in and start pumping out proinflammatory cytokines

Question 20

Randomized controlled intervention trial by You et al. (2004): getting sedentary people to exercise

Answer 20

Sample
-N=34 healthy, overweight, sedentary women
Intervention
-Hypocaloric diet alone (N=17) or diet with exercise (N=17) for 6 months
-Diet plus exercise group restricted their diet and walked on a treadmill 3 days/week for 20 – 60 mins
Hypothesis
-Combination of diet and exercise is more effective then diet alone in decreasing chronic inflammation
Inflammatory Outcomes
-CRP, IL-6, TNFα
Results
-Both groups lost a similar amount of body weight
-Diet plus exercise group had larger decrease in inflammatory markers compared to diet only
similar effects on weight but exercise had better effects on inflammatory markers

Conclusion of this study
-Exercise may have an effect above and beyond that of weight loss, perhaps due to decreased adipose tissue

Results: Changes in inflammatory markers in the diet (white) and diet plus exercise (black) groups
Bigger decrease in inflammation for exercise + diet group compared to exercise only, even though they lost the same amount of weight

Question 21

Randomized controlled intervention trial by Campbell et al. (2008)

Answer 21

Sample
-N= 202 sedentary men and women
Intervention
-Exercise group: 12 months of aerobic exercise 6x/week for 60 mins at 60-85% of maximal heart rate
-Control group: Asked to not change any health habits
Inflammatory outcome
-CRP
Results
-NO treatment effects on CRP levels
-NO intervention effects even after stratifying by baseline BMI, baseline CRP, and changes in body weight, body composition and aerobic fitness

-showing these effects are much more complicated than you would think

Question 22

Exercise guidelines

Answer 22

Department of Health and Human Services exercise guidelines for adults:

• 2.5 hours / week of moderate, or 75 mins/ week of vigorous aerobic physical activity
• Muscle-strengthening activities that involve all major muscle groups 2x/ week
• Aerobic activity should be performed in episodes of at least 10 minutes, preferably spread throughout the week

Question 23

Sleep guidelines

Answer 23

American Academy of Sleep Medicine recommends the following:
Get at least 7 hours of sleep per night!
Keep a consistent sleep schedule. Get up at the same time every day, even on weekends or during vacations.
If you don’t fall asleep after 20 minutes, get out of bed.
Limit exposure to light in the evenings.
Don’t eat a large meal before bedtime. If you are hungry at night, eat a light, healthy snack.
Avoid consuming caffeine in the late afternoon or evening.
Avoid consuming alcohol before bedtime.