Findings from the two studies point towards the vitamin’s intake as a lifelong process contributing to the healthy ageing process in cognitive as well as physical function.
“This study shows that vitamin D is associated with a health condition other than bone health,” said senior study author, Dr Eamon Laird, who led a Trinity College Dublin team in showing a 75% increased depression risk in vitamin D deficient patients over four-year follow up period.
“Our previous research has shown that one in eight older adults are deficient in the summer and one in four during the winter. Moreover, only around 8% of older Irish adults report taking a vitamin D supplement.”
Newborns and schizophrenia
Professor John McGrath from Aarhus University in Denmark found newborns with vitamin D deficiency had a 44% increased risk of being diagnosed with schizophrenia as adults compared to those with normal vitamin D levels.
“As the developing foetus is totally reliant on the mother's vitamin D stores, our findings suggest that ensuring pregnant women have adequate levels of vitamin D may result in the prevention of some schizophrenia cases,” he said.
“This is comparable to the role folate supplementation has played in the prevention of spina bifida."
The prevalence of deficiency particularly among vulnerable patient groups is likely due to several factors, including reduced capacity of the skin to synthesise vitamin D, malnutrition, reduced sun exposure, and impaired hydroxylation by the liver and kidney.
In later life, inadequate vitamin D has an impact on frailty status, bone health, cardiovascular disease, and mortality, and there is also growing interest in the link between vitamin D and late life mental health.
Older adults and depression
Dr Laird’s study looked at almost 4000 community-dwelling people aged 50 years and over. The longitudinal study examined the relationship between vitamin D levels at baseline (wave 1) and incident depression at 2- and 4-year follow-up (waves 2 and 3).
Whilst findings revealed the deficiency’s link to a 75% increase in the risk of developing depression by four years, the results also remained robust after controlling for a wide range of relevant factors.
These included depressive symptoms, chronic disease burden, physical activity and cardiovascular disease.
Furthermore, excluding participants taking anti-depressant medication and vitamin D supplementation from the analyses did not alter the team’s findings.
“The new finding that the development of depression could potentially be attenuated by having a higher vitamin D status could have significant policy and practice implications for Government and health services,” said principal investigator of the Study on Ageing (TILDA) at Trinity College Dublin, professor Rose Anne Kenny.
“It is our responsibility to now ascertain whether supplementation will influence depression. There are many reasons for vitamin D supplementation in Ireland. Benefits to something as disabling and often ‘silent’ as depression are therefore important for wellbeing as we age.”
Eight per cent of Danish schizophrenia cases
Meanwhile, Professor McGrath drew on findings from 2602 individuals to suggest that neonatal vitamin D deficiency could possibly account for about 8% of schizophrenia cases in Denmark.
"Much of the attention in schizophrenia research has been focused on modifiable factors early in life with the goal of reducing the burden of this disease," he said.
"Previous research identified an increased risk of schizophrenia associated with being born in winter or spring and living in a high-latitude country, such as Denmark.
Professor McGrath hypothesised that low vitamin D levels in pregnant women due to a lack of sun exposure during winter months might underlie this risk, and investigated the association between vitamin D deficiency and risk of schizophrenia.
"The next step is to conduct randomised clinical trials of vitamin D supplements in pregnant women who are vitamin D deficient, in order to examine the impact on child brain development and risk of neurodevelopmental disorders such as autism and schizophrenia," he added.
Source: Scientific Reports
Published online: DOI: 10.1038/s41598-018-35418-z
“The association between neonatal vitamin D status and risk of schizophrenia.”
Authors: Darryl Eyles et al.
Source: Journal of the American Medical Directors Association
Published online: doi.org/10.1016/j.jamda.2018.10.006
“Vitamin D Deficiency Is Associated With an Increased Likelihood of Incident Depression in Community-Dwelling Older Adults”
Authors: Robert Briggs et al.