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A prospective study of change in sleep duration: associations with mortality in the Whitehall II cohort

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A prospective study of change in sleep duration: associations with mortality in the Whitehall II cohort JE Ferrie*, MJ Shipley*, FP Cappuccio , EJ Brunner*, MA ... – PowerPoint PPT presentation

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Title: A prospective study of change in sleep duration: associations with mortality in the Whitehall II cohort


1
A prospective study of change in sleep duration
associations with mortality in the Whitehall II
cohort JE Ferrie, MJ Shipley, FP Cappuccio,
EJ Brunner, MA Miller, M Kumari, MG
Marmot International Centre for Health
Society, Department of Epidemiology Public
Health, University College London Cardiovascular
Medicine Epidemiology Group, Clinical Sciences
Research Institute, Warwick Medical School,
Coventry
2
Background
  • Inconsistent relationship between short sleep
    duration and all-cause mortality in populations
  • U-shaped effect
  • Kripke 1979 2002 Breslow 1980 Wingard 1983
    Gale 1998 Tamakoshi 2004 Patel 2004
  • Non uniform effect
  • Kojima 2000 Mallon 2002 Heslop 2002 Burazeri
    2003 Amagai 2004
  • No association
  • Kaplan 1987

3
Background
  • Inconsistent relationship between short sleep
    duration and all-cause mortality in populations
  • U-shaped effect
  • Kripke 1979 2002 Breslow 1980 Wingard 1983
    Gale 1998 Tamakoshi 2004 Patel 2004
  • Non uniform effect
  • Kojima 2000 Mallon 2002 Heslop 2002 Burazeri
    2003 Amagai 2004
  • No association
  • Kaplan 1987
  • Cause-specific mortality also inconsistent (some
    U-shaped)
  • Wingard 1983 Kripke 2002 Amagai 2004 Patel
    2004
  • One study indicates no association between
    increase or decrease in sleep over time and
    all-cause mortality
  • Heslop 2002
  • Finally, potential mechanisms underlying a
    U-shape curve with mortality may differ in short
    vs long-sleepers
  • Knutson 2006

4
Objective
  • To examine sleep duration and change in sleep
    duration as predictors of all-cause,
    cardiovascular and non-cardiovascular mortality
    in longitudinal data from the Whitehall II study
    of British civil servants

5
Whitehall II Cohort
  • White-collar British civil servants
  • Men and women aged 35-55 at entry

6
Measures (1)
  • Exposure sleep duration
  • Phase 1 How many hours of sleep do you have on
    an average night? Categories were lt5, 6, 7, 8,
    gt9h
  • Phase 3 On an average weekday how many hours do
    you spend on the following activities? a) work b)
    time with family c) sleep Responses were 1-12h
    and were collapsed to match Ph 1.
  • People on sleep medications (147 and 91) were
    included in lt5h.
  • Changes in sleep duration over time three
    categories
  • Sleeping less, the same or more at Ph3 than at
    Ph1
  • For decrease we pooled 6,7 and 8
  • For increase we pooled 5 and 6 (assuming
    beneficial effect on mortality), and 7 and 8
    (assuming detrimental effect on mortality)
  • Reference group for comparison those who slept
    the same

7
Measures (2)
  • Mortality
  • Through the NHS Central Registry
  • Censored at 30th September 2004
  • Mean follow-up 17.1 years from Ph1, 11.8 from
    Ph 3
  • Death certificates coded using 9th and 10th
    revisions of ICD
  • Cardiovascular (ICD-9 390-459 and ICD-10 I00-I99)
  • Non-cardiovascular (all remaining codes)

8
Measures (3)
  • Covariates and Risk factors
  • Socio-demographic factors
  • Age, employment grade, marital status
  • Existing morbidity
  • Modified GHQ score without sleep Qs, use of
    hypnotics, self-rated health, physical illness
    indicator (diabetes, heart trouble, ECG
    abnormalities, hypertension, respiratory
    illnesses), prevalent CHD
  • CVD risk factors
  • BMI, blood pressure, total cholesterol
  • Health-related behaviours
  • Cigarette smoking, high alcohol consumption,
    little exercise (lt1h of mod-to-vig exercise a
    week)

9
Analysis
  • Cox proportional hazard models
  • Follow-up as time scale
  • Hazard Ratio (95 CI)
  • 7h of sleep as reference category
  • Results identical in men and women, hence pooled
  • Two models
  • Age-adjusted
  • Fully-adjusted
  • Age, sex, marital status, employment grade,
    smoking, physical activity, alcohol consumption,
    self-related health, BMI, SBP, cholesterol,
    physical illness indicator, modified GHQ score,
    prevalent CHD

10
All-Cause mortality by hours of sleep
11
CVD mortality by hours of sleep
12
Non-CVD mortality by hours of sleep
13
All-cause mortality from Phase 3 by hours of
sleep at Phase 1 and 3
lt5h 6h 7h 8h
lt5h 4.3
6h 3.5
7h 2.3
8h 1.8
Phase 3
Phase 1
Age-standardised mortality rates per 1,000 person
years
14
All-Cause mortality from Phase 3 by the change in
sleep between Phase 1 and Phase 3
Age-adjusted Fully adjusted
15
CVD mortality from Phase 3 by the change in sleep
between Phase 1 and Phase 3
Age-adjusted Fully adjusted
16
Non-CVD mortality from Phase 3 by the change in
sleep between Phase 1 and Phase 3
Age-adjusted Fully adjusted
17
Summary
  • Either a decrease in sleep duration from a
    regular 6, 7 or 8h per night or an increase from
    a regular 7 or 8h per night predict all-cause
    mortality
  • A decrease in sleep duration affects all-cause
    mortality via increases in cardiovascular deaths
  • An increase in sleep duration affects overall
    mortality via an increase in non-cardiovascular
    deaths

18
Conclusions
  • People reporting decrease in sleep duration
    should be regarded as high risk groups for
    cardiovascular and all-cause mortality
  • Further work is required to determine which
    causes of death contribute most to the excess
    non-cardiovascular mortality among people whose
    sleep duration increases

19
Acknowledgements and disclosures
  • The Whitehall II study has been supported by
    grants from the MRC, BHF, HSE, DoH, NHLBI
    (HL36310) NIA (AG13196), Agency for Health Care
    Policy Research (HS06516) and the JD CT
    MacArthur Foundation Research Networks on
    Successful Midlife Development and Socio-economic
    Status and Health.
  • J.E.F. is supported by MRC, M.J.S. by BHF and
    M.G.M. by an MRC Research Professorship.
  • We thank all participating Civil Service
    departments and their welfare, personnel, and
    establishment officers the Occupational Health
    and Safety Agency the Council of Civil Service
    Unions all participating civil servants in the
    Whitehall II study all members of the Whitehall
    II study team.
  • F.P.C. holds the Cephalon Chair, an endowed post
    at Warwick Medical School, the result of a
    donation from the company. The appointment to the
    Chair was made entirely independently of the
    company and the postholder is free to devise his
    own programme of research. Cephalon do not have
    any stake in IP associated with the postholder
    and the Chair has complete academic independence
    from the company.
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