. 2016 Feb 17;6(2):e008119. doi: 10.1136/bmjopen-2015-008119

Table 3.

Characteristics of the studies included in the meta-analysis (in order of baseline year)

First author, publication year	Ascertainment of sleep (ref vs exposure)	Ascertainment of mortality	Adjustment for confounders
Kaplan, 1987⁴²	Questionnaire Nighttime sleep 7.0–8.0 vs <7.0 h 7.0–8.0 vs >8.0 h	Death certificate All cause	Age, self-reported health status
Kronholm, 2011²⁹	Questionnaire Nighttime sleep 7.0–8.0 vs ≤5.0 h 7.0–8.0 vs ≥10.0 h	Death certificate and hospital discharge register All cause and CVD	None
Gale, 1998⁴³	Questionnaire Nighttime sleep 9.0 vs ≤7.0 h 9.0 vs ≥12 h	Death certificate All cause	Age, sex, geriatrician’s diagnoses of illness, social class, systolic BP, BMI
Branch, 1984⁴⁴	Questionnaire Nighttime sleep 7.0–8.0 vs 1.0–6.0 h 7.0–8.0 vs >8 h	Death certificate All cause	None
Gangwisch, 2008⁴⁵	Questionnaire Nighttime sleep 7.0 vs ≤5.0 h 7.0 vs ≥9.0 h	Death certificate and proxy interviews All cause	Age, physical activity, smoking, depression, sex, education, living alone, low income, daytime sleepiness, nighttime awakening, ethnicity, sleeping pill use, BMI, diabetes, hypertension, general health, cancer
Mallon, 2002³⁰	Questionnaire Nighttime sleep 6.0–8.0 vs <6.0 h 6.0–8.0 vs >8.0 h	Death certificate All cause	Age, living alone, not being married, smoking, diabetes, CVD, depression, insomnia, BMI, joint pain, respiratory disease, gastrointestinal disease, habitual sleeping pills use, habitual snoring
Jung, 2013³⁹	Questionnaire Nighttime sleep 7.0–7.9 vs 6.0 h 7.0–7.9 h vs ≥9.0 h Daytime sleep None vs ≥0.5 h	Death certificate (90%), or notice from a family member or published obituary (10%) All cause	Age, nap duration, depression, exercise, education, smoking, alcohol consumption, hypertension, diabetes, coronary heart disease, stroke, cancer, sleep-related medications and postmenopausal oestrogen
Burazeri, 2003³⁶	Questionnaire Daytime sleep None vs ≥2.0 h	Death certificate All cause and CVD	Age
Rumble, 1992⁴⁶	Questionnaire Nighttime sleep 4.0–9.9 vs <4.0 h 4.0–9.9 vs ≥10.0 h	Death certificate and patient records All cause	Sex, health ‘risk’, sleep medication
Ruigomez, 1995⁴⁷	Questionnaire 24 h sleep 7.0–9.0 vs ≤5.0 h 7.0–9.0 vs >9.0 h	Death certificate All cause	Age, sex, education, perceived health status
Stone, 2009³⁴	Questionnaire Nighttime sleep 6.0–8.0 vs <6.0 h 6.0–8.0 vs >8.0 h 24 h sleep 8.0–8.9 vs <6.0 h 8.0–8.9 vs ≥10.0 h	Death certificate All cause, CVD, cancer and other	Age, BMI, history of at least one medical condition (diabetes, Parkinson's disease, dementia, COPD, non-skin cancer and osteoarthritis), CVD, hypertension, walks for exercise, alcohol use, smoking status, depression, cognitive impairment, oestrogen use, benzodiazepine use
Cohen-Mansfield, 2012⁴⁸	Questionnaire Nighttime sleep 7.0–9.0 vs <7.0 h 7.0–9.0 vs >9.0 h	Death certificate All cause	Age, sex, origin, marital status, education, income, had children, number of medications, comorbidity, subjective health, ADL and IADL limitations, cognitive difficulties, depressed affect
Kim, 2013⁴⁹	Questionnaire 24 h sleep 7.0 vs ≤5.0 h 7.0 vs ≥9.0 h	Death certificate All cause	Age, sex, ethnicity, education, marital status, hypertension, diabetes, alcohol consumption, energy intake, BMI, physical activity, hours spent daily watching television, smoking
Seki, 2001⁵⁰	Questionnaire 24 h sleep 7.0 vs <6.0 h 7.0 vs ≥9.0 h	Death certificate All cause	Age, sex, medical history (cerebrovascular disease, CVD, hypertension, diabetes, liver disease, renal disease, malignant neoplasm)
Lan, 2007³⁷	Questionnaire Nighttime sleep 7.0–7.9 vs <7.0 h 7.0–7.9 vs ≥10 h Daytime sleep None vs ≥2.0 h	Death certificate All cause, CVD and cancer	Age, marital status, monthly income, cigarette smoking, alcohol consumption, BMI, exercise, disease history (heart disease, stroke and cancer), depression, afternoon nap duration
Leng, 2014⁵¹	Questionnaire Daytime sleep None vs ≥1.0 h	Death certificate All cause	Age, sex, social class, educational level, marital status, employment status, BMI, physical activity level, smoking status, alcohol intake, depression, self-reported general health, hypnotic drug use, antidepressant use, COPD drug use, time spent in bed at night, self-reported pre-existing diseases, sleep apnoea
Yeo, 2013⁵²	Questionnaire 24 h sleep 7.0 vs ≤5.0 h 7.0 vs ≥10.0 h	Death certificate All cause, CVD, cancer, external cause, respiratory disease and other	Sex, educational attainment, BMI, cigarette smoking, alcohol consumption, hypertension, diabetes, CVD, metabolic syndrome
Kakizaki, 2013³¹	Questionnaire 24 h sleep 7.0 vs ≤6.0 h 7.0 vs ≥10.0 h	Death certificate All cause, CVD, cancer and other	Age, sex, total caloric intake, BMI, marital status, education, job status, history of myocardial infarction, history of cancer, history of stroke, hypertension, diabetes, smoking, alcohol consumption, time spent walking, perceived mental stress, self-rated health
Werle, 2011⁴⁰	Questionnaire Nighttime 24 h sleep ≤8.0 vs >8.0 h	Death certificate, proxy interviews and patient records All cause and CVD	Age, sex, education, number of family members living with the elderly, smoking, physical activity, BMI
Kripke, 2011³³	Questionnaire and actigraphy Nighttime sleep 7.0 vs ≤5.0 h 7.0 vs ≥9.0 h	Proxy interviews and social security death index All cause	None
Castro-Costa, 2011²⁴	Questionnaire Nighttime sleep 7.0–7.9 vs <6.0 h 7.0–7.9 vs ≥9.0 h	Death certificate and proxy interviews All cause	Age, schooling, marital status, working status, education, alcohol consumption, coffee consumption, smoking, physical exercises, depressive symptoms, cognitive functioning, psychoactive medications, physical functioning, arthritis ascertainment, systolic BP, HDL cholesterol ratio, diabetes, BMI
Chen, 2013⁵³	Questionnaire Nighttime sleep 7.0 vs ≤4.0 h 7.0 vs ≥9.0 h	Death certificate All cause and CVD	Age, sex, living status, marital status, education, BMI, insomnia, excessive daytime sleepiness, pain, smoking, alcohol drinking, snorers, diabetes, hypertension, CVD, stroke, gouty arthritis, depression, hypnotics, total sleep time
Suzuki, 2009⁴¹	Questionnaire 24 h sleep 7.0 vs ≤5.0 h 7.0 vs ≥10.0 h	Death certificate All cause and CVD	Age, sex, BMI, smoking status, alcohol consumption, frequency of physical activity, socioeconomic status, mental health, hypertension, diabetes
Ensrud, 2012³⁵	Actigraphy 24 h sleep >5.0 vs ≤5.0 h	Death certificate and proxy interviews All cause	Age, race, site, health status, BMI, education, social support, alcohol intake, smoking, antidepressant, benzodiazepine, non-benzodiazepine sedative hypnotic use, medical conditions, cognition, baseline frailty status
Mesas, 2010⁵⁴	Questionnaire 24 h sleep 7.0 vs ≤5.0 h 7.0 vs ≥11.0 h	Death certificate All cause	Age, sex, BMI, educational level, municipality of residence, physical activity, smoking, alcohol consumption, coffee consumption, social links, perceived health, MMSE score, depression, Medical Outcomes Study 36-item Short Form Survey Physical and Mental Component Summary scores, instrumental activity of daily living limitations, hypertension, ischaemic heart disease, stroke, diabetes, cancer, COPD, Parkinson’s disease, arousal from sleep at night, use of anxiolytic medication
Lee, 2014³⁸	Questionnaire Nighttime sleep <10.0 vs ≥10.0 h	Death certificate All cause	Age, smoking, mood, overweight (BMI>23), medical conditions (diabetes, heart disease, history of cancer, COPD, history of stroke), frailty
Zuurbier, 2015³²	Questionnaire and actigraphy 24 h sleep 6.0–7.5 vs<6.0 h 6.0–7.5 vs >7.5 h	Death certificate and patient records All cause	Age, sex, ADL, smoking, diabetes, myocardial infarction, stroke, cognitive functioning, depressive symptoms, BMI, sleep medication, napping, apnoea

ADL, activities of daily living; BMI, body mass index; BP, blood pressure; COPD, chronic obstructive pulmonary disease; CVD, cardiovascular disease; HDL, high-density lipoprotein; IADL, instrumental activities of daily living; MMSE, Mini-Mental State Examination; Ref, reference.