Presented at the annual meeting of the American Association for Public Opinion Research

Austin, Texas May 13, 2016

David Cloud, Kristen Knutson – National Sleep FoundationJulie E. Phelan, Gary Langer – Langer Research Associates

The Sleep Health Index ™

A Brief History of Polling at the National Sleep Foundation

Kristen Knutson, PhD

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The Sleep in America (SIA) Poll

• Started in 1990• Released during Sleep Awareness Week • Goal: To increase media and public awareness

of sleep

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The Sleep in America (SIA) Poll

• Surveyed sub-sections of Americans on sleep-related topics (N~1000 respondents)

Year Topic Sample2002 Sleep in Adults >18y2003 Sleep in Older Adults 55-84 y2004 Sleep in Kids <10 y2006 Sleep in Adolescents 11-17 y2007 Sleep in Women 18/-64 y; Women 2008 Sleep in Full-time workers >18 y & work ≥30 h/week2010 Sleep & Race/Ethnicity 25-60 y; White, Black, Asian or

Hispanic2011 Bedroom Environment 25-55 y2012 Sleep & Transportation Workers Pilots, truck drivers, train

operators and bus, taxi & limo drivers

2013 Sleep & Exercise 23-60 y

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SIA Poll Challenges

• Questionnaire Design– Question wording, responses, recall

• Minimal disclosures of methodology • Not representative samples (nonprobability

sampling)• Polls cannot be compared to each other.

– Variability in sample, topic, task force.– No trends can be detected

• Lack of systematic process for archiving poll materials

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NSF Faces these Challenges

• Hired outside group to audit the Poll.• Led to:

– Polling expert consultant – Creation of SIA Poll Fellow– Use AAPOR standards to disclose methodology– Increase scientific rigor (e.g. probability-based

sampling)– Archive materials including data files, press

releases, questionnaire and methods reports

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Sleep Health Index™ Overview• Developed over the course of a year• Involved input from many different perspectives

including sleep researchers, doctors, methodologists, and pollsters

• Addressed the limitations of the Sleep in America Poll– Probabilistic – Same population– Same questions– Significantly shorter

• Surveys 1,000 Americans on a quarterly basis • Track trends over the years and seasons• Calculates a ‘Sleep Health Grade’

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Creating the Sleep Health Index• Resources- SIA Poll Scholar, Consultants, Task Force• Question development and refinement • Cognitive testing • Pre-testing• Question refinement • Years 1 and 2 of data collection • Question refinement • Index creation – Langer Research Associates

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Construction and Validation of the Sleep Health Index

Julie Phelan, PhD

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Objective• Create a robust, clear and concise tool to assess sleep health

• Use existing data from the two national surveys conducted for the Foundation in 2014 and 2015– random-sample landline and cellphone interviews– 28 substantive questions about sleep– 2,503 respondents

• Test the SHI’s reliability and validity

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Index Construction• 14 of the 28 questions were selected on a conceptual and

empirical basis

• Factor analysis identified three distinct constructs related to sleep health: sleep quality, sleep duration and sleep disorders

• Cronbach’s alphas confirmed the internal consistency of these subindices: α= .63 to .77

• Virtually identical Cronbach’s alphas in 2014 and 2015 data indicated reliability over time

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Sleep Quality Subindex

Simple average of scores assigned to six items:

• Self-assessed ratings of sleep quality

• Number of days in the past seven the respondent:– had trouble falling asleep– had trouble staying asleep– was negatively impacted by lack of sleep– dozed unintentionally– felt well-rested (reverse coded)

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Disordered Sleep SubindexSimple average of scores assigned to three items:

• Number in the past seven the respondent took a sleep medication

• Whether or not the respondent reported having a sleep disorder

• Whether or not the respondent has discussed sleep problems with a doctor

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Sleep Duration SubindexSimple average of scores assigned to three items:

• Weekday sleep score: how well self-reported weekday time in bed aligns with expert recommendations for optimal sleep

• Sleep deficit score: how well respondents’ approximate weekday sleep aligns with the amount of sleep they say the need to feel their best

• Social jetlag score: how well respondents’ weekday time in bed aligns with their weekend time in bed

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Sleep Health Index Scores

0102030405060708090

100

7769

80 8275

6879 80

2015 2014

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Distribution of SHI Scores

Grade: A_x000d_(90-100)

Grade: B_x000d_(

80-89)

Grade: C_x000d_(

70-79)

Grade: D_x000d_(

60-69)

Grade: F_x000d_(

<60)

0%

10%

20%

30%

40%

50%

24% 27%

19%14% 17%

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Sleep Quality (Score 68)

Excellent: 11%

Very good: 19%

Good: 35%

Fair: 22%

Poor: 12%

NET: 33% NET: 31%

Item score: 49

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Add’l Sleep Quality Items: Days in Past 7 Resp.

0

1

2

3

4

5

6

7

3.9

2.11.7 1.5 1.3

55 69 76 78 82

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Disordered Sleep (Score 81)

Took sleep medication0

1

2

3

4

5

6

7

0.8

# of days out of the past seven…

89

a diagnosed sleep disorder

spoken with a doctor about sleep issues

0%10%20%30%40%50%60%70%80%90%

100%

15%

27%

85 69

% who have…

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Sleep Duration (Score 79)

0%

10%

20%

30%

40%

50%

5% 6%

15%

27% 25%

14%9%

Time in Bed average: 7.7 hours

TIB score: 67

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Sleep Duration Deficit …and Social Jetlag

None <1 hr 1 to <2 hrs

2+ hrs

0%

10%

20%

30%

40%

50%

28% 29%24%

20%

Score: 84

Average: 1.1 hours

1 hr or less

1 to <2 hrs

2+ hrs0%

10%

20%

30%

40%

50%

60%

70%

51%

26%22%

Average: 1.1 hours

Score: 88

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Testing Construct Validity

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SHI by Overall Health

0102030405060708090

10081 76 80

88

6451

7766

Excellent/very good health

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SHI by Stress

0102030405060708090

100

6754

73 7481 77 82 84

Extremely/very stressed

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SHI by Life Satisfaction

0102030405060708090

10080 74

81 84

6146

69 66

Extremely/very satisfied

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SHI by “How you’d use an extra hour”

0102030405060708090

100

6756

71 747871

80 82

Sleep Something else

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SHI by Mattress Comfort

0102030405060708090

100

7770

80 82

6553

73 72

Very/fairly comfortable mattress

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Sleep Quality by Sleep Disorders

Sleep disorder? Talk to doctor? Sleep medication?0102030405060708090

100

56 57 54

71 73 71

Yes No

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Predicting the SHI

• Strongest predictors: stress and overall health– Stress predicts all three subindices, sleep quality most strongly – Health predicts sleep quality and disorders, not duration. (Poor

health is linked with sleeping too much or too little, hence a non-linear relationship)

• Weaker predictors:– Life satisfaction (predicts quality and duration, not disorder)– Frequency of texting or emailing after initially falling asleep

(predicts quality and duration, not disorder– Mattress comfort (predicts quality, not duration or disorder)– Employment (predicts duration)– Age (predicts disorder)

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Conclusions

• The Sleep Health Index demonstrates strong empirical reliability and validity

• It provides a simple way to:– summarize the nation’s sleep health overall and in three

separate but related elements - quality, duration and disorders– track sleep health over time and across groups of interest– assess the relationship between sleep health and key variables,

either asked alongside the index questions or – as time trend develops – from external data sources

• Quarterly calculation of the SHI is now underway