Table 1.

Longitudinal studies with diet as a confounder or an independent risk factor

Author, Year, Country	Study population	Study design	Sleep Assessment	Confounder Assessment	Outcome Assessmenta,b	Other Covariates	Statistical Analysis	Main findings
Children and adolescents
Baird, 2016, UK [20]	587 children, aged 3 years at baseline	Population-based longitudinal study of mothers and children followed from preconception	Sleep duration, including nighttime sleep and daytime naps, at age 3; parent-report	Diet quality at age 3, Prudent diet z-score; FFQ	BMI (height and weight); body composition (fat and fat-free mass index by DXA scan) at age 4	Gestational age (GA), age at DXA, sex, pre-pregnancy maternal BMI, maternal education, prenatal smoking, parental SES, age last breastfed, activity level, TV watching time	Linear regression	Shorter sleep was associated with higher BMI, a greater fat mass index, and a greater fat-free mass index one year later; adjustment for confounders did not substantially alter estimates; diet was independently associated with adiposity
De Souzab, 2015, Portugal [21]	6,894 adolescents, aged 10–18 years at baseline	Longitudinal study, annual measurements for 3 years	Sleep duration during the week; self-report	Fruit and vegetable intake (dichotomo us variable: every day vs. not every day); FFQ	BMI	Physical activity, physical fitness	Sex-stratified hierarchical linear models to model change in BMI	Sleep duration was not associated with BMI trajectories in fully adjusted models (crude association not reported)
Fairleyb, 2015, UK [24]	987 participants, aged 3 years	Longitudinal multiethnic birth cohort	Sleep duration during day and night at 24 months; parent-report	Duration of any breastfeeding, age at weaning on to solids, infant’s total energy intake per day, infant’s total protein intake per day, caregivers feeding style; parent reported	BMI z-scores and child overweight; measured at the 36 month visit, based on the WHO 2006 growth standards	Ethnicity, infant sex, maternal age, maternal highest educational qualification, parity, birthweight, gestational age at delivery, mode of delivery	Linear regression models and Poisson regression models	No association between sleep duration and BMI-z scores (unadjusted analyses not shown). BMI z-scores were higher in children who breastfed between 1 day and 1 month (compared to those who never breastfed) and had an indulgent caregiver’s feeding style; similar patterns for overweight
Shang, 2014, Canada [23]	613 children, aged 8–10 years	Longitudinal study of families	Sleep duration; 7-day actigraphy	3 dietary patterns (traditional, healthy fast food); total energy intake; 24-hr recalls	BMI, WC, fat mass %, obesity defined as ≥ 95th percentile for age and sex	Age, sex, screen time, mother’s obesity, family income, daily steps; sweetened beverage intake	Multivariable logistic regressions	In fully adjusted multivariable models, fast food dietary pattern was associated with overweight and adiposity measures (BMI, WC, body fat mass %), sweetened beverage intake was associated with BMI and WC, but sleep duration was not significantly associated with adiposity (crude association not shown)
Lytle, 2013, USA [22]	723 adolescents, mean age 14.7 years at baseline	Longitudinal study; one follow-up visit 2 years after baseline	Change in average daily sleep duration over follow-up; self-report	Total energy intake; average daily calories from three 24-h recalls via phone (two weekdays and a weekend)	BMI and % body fat; body size via bioelectrical impedance and hydrodensitometry	Sex, grade level, depression, screen time/sedentary behavior, physical activity, puberty, race, SES, parental education, study	Random coefficient models to account for within-person correlation, all conducted separately for males and females	Change in sleep duration was not associated with change in adiposity measures over two years, neither in analysis adjusting only for sociodemographic characteristics nor in fully adjusted analysis.
Adults
Byrneb 2016, USA [25]	10,248 employees of Vander bilt University, mean age 41 years	Longitudinal study, annual participation in health risk assessment	Sleep 7-8h per night (range from seldom or never to always); self-report	Dietary fat intake, unhealthy snacks, breads and grains, fruits and vegetables, regular breakfast; self-report	Cardiometabolic outcomes: hypercholester olemia, hypertension, obesity, diabetes mellitus, heart disease, stroke; self-report	Age, sex, race/ethnicity, physical activity, smoking, strength exercising, baseline BMI and comorbidities	Multivariable Cox regression, excluding individuals with outcomes at baseline	“Always” sleeping 7–8h per night compared to “never” was associated with lower risk of obesity, heart disease, hypercholester olemia, and stroke even after accounting for diet (largest effect estimate with high-fat diet) and other covariates
Hoevenaar-Blom, 2014, The Netherlands [27]	17,887 adults age 20-79 years	Longitudinal study, 10–14 year follow up	Sleep duration (sufficient (≥7 h) versus insufficient); self-report	Mediterranean diet intake; FFQ	CVD events and mortality	Age, sex, physical activity, smoking, education, BMI, blood pressure, alcohol	Cox proportional hazards, Preventable fraction calculated	Sufficient sleep in addition to the healthy lifestyle score significantly reduced the hazard of CVD deaths or events (unadjusted estimates not substantially different from adjusted)
Li, 2014, Japan [28]	12,883 adults aged 20–79 year at baseline	Longitudinal study with a 10-year follow-up	Sleep duration (<6h vs. ≥ 6 h); self-report	3 dietary patterns: traditional, healthy, Western; FFQ	Diabetes mellitus, general CVD events and deaths	Occupation, age, current smoking, habitual drinking, regular physical activity, work intensity BMI, systolic BP, total cholesterol, and fasting blood glucose	Cox proportional hazard regression and logistic regression to predict 10-year risk of CVD events	Short sleep duration, traditional and Western diet were associated with CVD events after controlling for other lifestyle factors
Restall, 2014, multi-country: Australia, New Zealand, Ireland [29]	1,950 nulliparous women, mean age 29 years, 14–16 weeks pregnant with a singleton	Longitudinal, multi-center cohort study, 2004–2011	Nightti me sleep duration hours (<8h (referen ce), 8-9h, ≥10h); self report	Fish/seafood (including oily fish such as tuna or salmon and shellfish or shrimps) weekly intake (<3 vs. ≥3 servings); self-report	Excessive gestational weight gain (yes vs. no) according to Institute of Medicine 2009 guidelines	Exercise, infertility, behavioral responses to illness, smoking, immigration status, birth weight	Logistic regression;	High fish/seafood intake and sleeping for 10h+ per night were each associated with higher risk for excessive weight gain in pregnancy (unadjusted associations not shown)
Sayon-Orea, 2013, Spain [26]	10,532 adults (n=9,470 for naps data), mean age 39 years at baseline	Longitudinal study, followed for median 6.5 years	Average night sleep duration (reference = 7–8 h) and average nap duration (reference=never/almost never nap); self report	Total energy intake, sugar-sweetened beverage intake, fast food intake, snacking between meals; FFQ	Incidence of obesity over follow-up period; self-reported height and weight	Age, sex, physical activity, smoking, sitting, regular snoring, insomnia, caffeine intake, alcohol intake, baseline BMI	Cox regression model	Sleeping <5 h per night was associated with higher risk of developing obesity and a nap of 30 min/day was associated with lower risk of developing obesity, accounting for potential confounders did not substantially alter estimates (except for adding baseline BMI).

BMI=Body Mass index; CDC=Centers for Disease Control; CHO=carbohydrate; FFQ= food frequency questionnaire; IOM=Institute of Medicine; IOTF=International Obesity Taskforce; MetS=metabolic syndrome; SES=socioeconomic status; TV=television; UK=United Kingdom; USA=United States of America; WC=waist circumference; WHO=World Health Organization

^aOverweight defined as BMI≥25 and obesity defined as BMI≥30, WC≥40 in men, WC≥35 in women unless otherwise specified

^bIndicates a study where sleep was one of many risk factors (including nutrition) considered for cardiometabolic outcome