Iron, Vitamin D Deficiency May Contribute to Poor Sleep Health in Reproductive-Aged Women

Ana Baylin, MD, DrPH
Credit: University of Michigan

A new report from a team at the University of Michigan School of Public Health provides insight into the effects of iron and vitamin D deficiencies on sleep health and quality in women.

An analysis of data from the National Health and Nutrition Examination Survey (NHANES), results of the study, which included more than 9000 reproductive-aged women, suggest the presence of iron deficiency and iron deficiency anemia were associated with an increased risk of poor sleep quality while the presence of vitamin D deficiency and vitamin D inadequacy was associate with an increased risk of shorter sleep duration.¹

“In this study, we examined the cross-sectional association of iron and vitamin D deficiencies and inadequacies with sleep duration, latency, and quality in a representative sample of the US women of reproductive age. We found that [iron deficiency/iron deficiency anemia] was associated with sleep quality while [vitamin D deficiency/vitamin D inadequacy] was associated with sleep duration, which emphasizes the importance of assessing different sleep dimensions when studying sleep health,” wrote investigators.¹

Launched in the 1960s, NHANES is a program of studies designed to assess the health and nutritional status of adults and children in the United States. A combination of interviews and physical examinations, the survey became a continuous program in 1999 and examines a national representative sample of approximately 5000 people each year.²

For the purpose of analysis, a team of investigators led by Ana Baylin, MD, DRph, created 2 sample cohorts of women aged 20-49 years old who were not pregnant. The first cohort contained 2497 women from survey cycles occurring between 2005 and 2009. The second cohort contained 6731 women from survey cycles 2005 and 2010 and 2015 and 2018. Investigators pointed out sociodemographic characteristics of the 2 samples were comparable. Overall, 12.8% of females had iron deficiency, 6.0% had iron deficiency anemia, 7.6% had vitamin D deficiency, and 30.1% had vitamin D inadequacy.¹

Investigators noted sleep outcomes were measured using a self-reported questionnaire. Investigators also pointed out the body iron model based on serum ferritin and serum soluble transferrin receptor to identify iron deficiency and also with hemoglobin to identify iron deficiency anemia cases. Investigators used 25-hydroxyvitamin D levels were used to determine vitamin D deficiency and vitamin D inadequacy cases.¹

Initial analysis revealed 25.9% of women reported short sleep duration, 20.2% reported long sleep latency, and more than half reported poor sleep quality. Upon analysis, results suggested iron deficiency (Odds Ratio [OR], 1.42; 95% Confidence Interval [CI], 1.02-2.00) and iron deficiency anemia (OR, 2.08; 95% CI, 1.29-3.38) were associated with poor sleep quality. Further analysis revealed vitamin D deficiency (OR, 1.26; 95% CI, 1.02-1.54) and vitamin D inadequacy (OR, 1.22; 95% CI, 1.04-1.44) were significantly associated with short sleep duration.¹

Additionally, investigators noted women with both nutritional deficiencies had significantly greater odds of poorer sleep quality compared to subjects with neither condition. Investigators also called attention to a significant multiplicative interaction observed between iron deficiency and vitamin D deficiency (P=.0005).¹

“Among women of reproductive age, iron and vitamin D deficiencies are associated with sleep health outcomes. The potential synergistic effect of both deficiencies warrants further assessment,” investigators wrote.¹

References:

1. Al Hinai M, Jansen EC, Song PXK, Peterson KE, Baylin A. Iron Deficiency and Vitamin D Deficiency Are Associated with Sleep in Women of Reproductive Age: An Analysis of NHANES 2005-2018 Data. J Nutr. Published online November 30, 2023. doi:10.1016/j.tjnut.2023.11.030
2. Nhanes - about the National Health and Nutrition Examination Survey. Centers for Disease Control and Prevention. May 31, 2023. Accessed December 7, 2023. https://www.cdc.gov/nchs/nhanes/about_nhanes.htm.