Table 3.
Characteristics of included cohort studies
| No. | Study (year) | Country | Population | Exposure | Sleep outcome | Adjusted variables | NOS scorea | Main result |
|---|---|---|---|---|---|---|---|---|
| Infants and toddlers (aged 0–3 y) | ||||||||
| 1 | Cheruku et al (2002)42 | United States | Healthy pregnant women (n = 17) and their new-born children | High DHA level: Maternal plasma phospholipid fatty acid concentration > 3.0% by weight of total fatty acids | Neonates’ AS, QS, sleep-wake transition, and wakefulness measured with actigraph | Maternal age, race, parity, length of gestation, maternal education, infant birth weight, infant birth length, infant head circumference, 1-min Apgar score, 5-min Apgar score |
Total: 5 S: 4, C: 1, O: 0 |
On postpartum day 1, the ratio of maternal n-6 to n-3 fatty acids in maternal plasma was negatively associated with QS and positively associated with arousals in QS. On postpartum day 2, maternal n-6: n-3 was positively associated with AS (r = 0.53, P < 0.05), sleep-wake transition (r = 0.52, P < 0.05), and AS: QS (r = 0.52, P < 0.05). On postpartum day 2, maternal DHA concentration was negatively associated with AS (r = 0.49, P < 0.05), AS: QS (r = 0.55, P < 0.05), and sleep-wake transition (r = 0.49, P < 0.05) and positively associated with wakefulness (r = 0.51, < 0.05). |
| 2 | Zornoza-Moreno et al (2014)52 | Spain | Pregnant women (n = 63) both healthy and with GDM, and their infants | Venous cord plasma DHA percentages in women with GDM treated with diet and insulin | Infants’ sleep rhythm maturation (ie, IS, and CFI) estimated from body temperature and physical activity | Exposure duration: the whole pregnancy period. Follow-up time points: at birth; 15 d; 1, 3, and 6 mo after birth; but only data at 3 and 6 mo were reported |
Total: 7 S: 4, C: 1, O: 2 |
Maternal DHA level at recruitment correlated with children’s better sleep rhythm maturation at 6 mo of age, as indicated by higher IS (r = 0.383, P = 0.007) and CFI (r = 0.340, P = 0.018). |
| 3 | Kocevska et al (2016)53 | Netherlands | Children (n = 3465) aged 1–3 y | Daily nutrient intake | Parent-reported questionnaires regarding total sleep duration, number of night awakenings, usual bedtime, wake-up time, and daytime napping | Maternal parity, age, marital status, education, household income, maternal smoking during pregnancy, children’s sex and birth weight, ethnic group, breastfeeding history, child behavior problems, family regularity, time spent watching television at age 2 y |
Total: 6 S: 3, C: 1, O: 2 |
Substituting unsaturated fat intake with saturated fat was associated with 7 min (95%CI, −13 to −1 min) shorter TSD at age 3 y for each 5% of energy from saturated fat. Vice versa, substituting saturated with unsaturated fat was associated with 5 min (95%CI, 2–8 min) longer nighttime sleep duration at age 3 y |
| Children (aged 4–18 y) | ||||||||
| 4 | Huss et al (2010)54 | Germany | Children aged between 5 and 12 y (n = 810) and referred to primary care settings for attentional and behavioral problems | Food supplement containing a combination of omega-3 (EPA 400 mg +DHA 40 mg) and omega-6 fatty acids (60 mg) as well as magnesium (80 mg) and zinc (5 mg) | Pediatricians’ documentation of sleep-related problems (ie, problems falling asleep, sleeping through the night, and impaired sleep quality) | Child sex and age groups |
Total: 6 S: 3, C: 1, O: 2 |
The number of children evaluated as having problems falling asleep, having problems to sleep through the night, and having impaired sleep quality were 305 (38.3%) and 182 (22.9%), 148 (18.6%) and 87 (10.9%), and 186 (23.7%) and 107 (13.6%), before and after intervention, respectively (P < 0.001 for all). Improvement of sleep-related symptoms was similar in all age groups but more statistically significant for girls regarding to difficulty falling asleep. |
| 5 | Liu et al (2017)56 | China | Chinese children aged 9–11 y (n = 541) | Fish consumption data at age 9–11 y were obtained from a self-administrated food frequency questionnaire | Sleep quality was measured by the total sleep disturbance score derived from parental report of sleep patterns in the CSHQ | Parental education, occupation, marital status, maternal age at childbirth, home location, breastfeeding history, child sex and siblings, and breakfast consumption |
Total: 6 S: 3, C: 1, O: 2 |
Sleep disturbance score in children who frequently ate fish (≥ 1/wk) was 4.49 (P = 0.001, Cohen d = 0.221) and in children who sometimes ate fish (2–3 times per mo) was 3.01 (P = 0.019, Cohen d = 0.132), lower than those who never or seldom ate fish. |
| Adults (aged > 18 y) | ||||||||
| 6 | Christian et al (2016)59 | United States | Pregnant women (n = 135) | RBC PUFA status | Pregnant women’s self-reported sleep quality measured by PSQI | Age, race/ethnicity, education, annual household income, gravidity, and parity, Pre-pregnancy BMI, |
Total: 6 S: 4, C: 1, O: 1 |
Higher RBC DHA levels were associated with significantly better overall sleep quality, as indicated by lower total scores on the PSQI (b = −1.00, P = 0.012), longer sleep duration (P = 0.019), and better sleep efficiency (P = 0.047). Neither EPA nor AA was associated with overall sleep quality (P ≥ 0.34). After adjusting for covariates, higher DHA:AA ratios were associated with better overall sleep quality (b = −15.4, P = 0.005), shorter sleep latency (P = 0.033), longer sleep duration (P = 0.019), and better habitual sleep efficiency (P = 0.026). |
| 7 | Lotrich et al (2016)58 | United States | Nondepressed adult patients aged between 18 and 80 y with HCV (n = 104) who received IFN-α therapy | RBC PUFA status | Patients’ self-reported sleep quality measured by PSQI | Sex, race, age, weight, baseline Beck Depression Inventory score |
Total: 6 S: 4, C: 1, O: 1 |
The PSQI score was 6.6 ± 4.1; the correlation with AA/(EPA+DHA) was 0.31 (P < 0.05). |
| 8 | Ford et al (2016)60 | United States | Participants (n = 8771) older than 30 y who completed the AHS-2 and the PsyMRS cohort studies | Daily dietary intake | Participants reported on questionnaires the duration of sleep at night categorized as < 6, 7–8, and ≥ 9 h. | Age, sex, ethnicity, BMI, education level, frequency of vigorous exercise, alcohol intake, Mediterranean diet pattern, total energy intake |
Total: 7 S: 4, C: 1, O: 2 |
The correlation coefficient between hours of sleep and omega-3 PUFA exposure was β = 0.24, B = 0.15 (95%CI, 0.08–0.22), P < 0.001. |
a
The NOS checklist was used to evaluate the quality of included cohort studies.
Abbreviations: AHS-2, Adventist Health Study-2; AS, active sleep; BMI, body mass index; C, comparability; CFI, Circadian Function Index; CSHQ, Children’s Sleep Habits Questionnaire; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; GDM, gestational diabetes mellitus; HCV, hepatitis C virus; IFN-α, interferon-α; IS, inter-daily stability of the rhythm; O, outcome; NOS, Newcastle-Ottawa Scale; PSQI, Pittsburgh Sleep Quality Index; PsyMRS, Psychosocial Manifestations of Religion Sub-Study; PUFA, polyunsaturated fatty acid; QS, quiet sleep; RBC, red blood cell; S, selection; TSD, total sleep duration.