Maternal tryptophan levels tied to sleep quality in pregnancy
Women with higher plasma tryptophan concentrations were less likely to have poor sleep quality during pregnancy, especially among those with anxiety symptoms, according to the GUSTO* study.
“These findings suggest the importance of having adequate tryptophan concentrations during pregnancy,” said the researchers led by Dr Mary Chong of Saw Swee Hock School of Public Health at National University of Singapore.
The study included 572 pregnant Asian women in Singapore who were assessed for plasma tryptophan concentrations at 26–28 weeks gestation. They also underwent sleep and psychological assessments using the Pittsburgh Sleep Quality Index (PSQI), the State-Trait Anxiety Inventory, and the Edinburgh Postnatal Depression Scale at 26–28 weeks gestation and 3 months after delivery. [J Affect Disord 2018;225:523-529]
For each 10 µmol/L increase in maternal plasma tryptophan levels at 26–28 weeks gestation, the prevalence of poor sleep quality during pregnancy dropped by 12 percent (adjusted prevalence ratio [PR], 0.88 per 10 µmol/L; p=0.008), after adjusting for covariates such as age, ethnicity, physical activity, smoking habits, and household income.
The association between maternal tryptophan levels and poor sleep during pregnancy was particularly evident in those with probable anxiety (PR, 0.79 per 10 µmol/L; p=0.008). While the association was also observed among women with probable depression, this was not statistically significant after adjustment for covariates (PR, 0.70 per 10 µmol/L; p=0.115).
“Pregnant women commonly report sleep difficulties, which is in part due to the many physical and psychologic changes during pregnancy,” according to Chong and co-authors. “Lowering poor sleep quality and mental disorders is of vital importance as it reduces the risk for postnatal mental distress and promotes maternal and offspring health.”
Looking at the PSQI subcomponents, the researchers found that women with higher tryptophan levels scored lower on subjective sleep quality disturbance (adjusted odds ratio [OR], 0.77; p=0.021), habitual sleep efficiency (OR, 0.75; p=0.019), and sleep disturbances (OR, 0.79; p=0.035).
There was no association between tryptophan levels during pregnancy and sleep quality or mental health after delivery, to which the researchers attributed to the lower number of participants with postnatal data available (n=246).
“Tryptophan is involved in brain serotonin availability, which influences sleep latency. Furthermore, serotonin is the precursor for the hormone melatonin, which is involved in circadian rhythms including sleep quality,” suggested the researchers regarding the possible mechanism underlying the association. [Neurosci Biobehav Rev 34:387-407; Nutr J 2014;13:106]
As plasma tryptophan concentrations, sleep quality, and mental well-being were assessed at the same time point, the researchers acknowledged that no causal relationship can be inferred. Also, sleep quality and mental mood were self-reported, which may limit the findings.
“These results might be useful to design future dietary interventions in pregnant women suffering from poor sleep quality, particularly together with anxiety symptoms,” said Chong and co-authors.