ISLAMABAD, May 20 (Online): Around 1 in 5 adults in the U.S. who get COVID-19 eventually develop long COVID, according to the Centers for Disease Control and Prevention (CDC) Trusted Source.
But long COVID affects 50% to 70% of people who’ve been hospitalized with COVID-19, according to a new study that explores a link between vitamin D deficiency and long COVID.
The researchers looked at vitamin D levels of people with COVID-19 upon hospital admission and again six months after discharge. They observed that those with long COVID had lower levels of vitamin D than those who did not have the condition.
Lead investigator Dr. Andrea Giustina, professor of endocrinology and metabolism at the University Vita-Salute San Raffaele, in Milan, Italy, told Medical News Today:
“The clinical area of long COVID in which we found a more relevant influence of low vitamin D was the neurocognitive one.”
The findings of the research were recently published in The Journal of Clinical Endocrinology & Metabolism.
What is long COVID?
The World Health Organization (WHO)Trusted Source defines long COVID as a continuation or appearance of COVID-19-related symptoms within three months of an acute SARS-CoV-2 infection. The symptoms, which may last for two months or longer, have no other explanation.
The National Institutes on Aging (NIH)Trusted Source describes the following symptoms of long COVID:
• feeling tired or fatigued
• having difficulty breathing or shortness of breath
• coughing
• experiencing joint pain and weakness
• having hypertension
• noticing changes to smell, taste, or both
• confusion, forgetfulness, or brain fog
Linking long COVID to low vitamin D
For the study, researchers recruited 50 people diagnosed with long COVID and 50 people who did not develop the condition from an outpatient clinic associated with San Raffaele Hospital in Milan.
Individuals in the two groups were matched one to one, taking into account the severity of their illness from COVID-19, as well as age, sex, and any preexisting chronic conditions.
The close matching of people with and without long COVID was a means to avoid as many influencing factors as possible that might confuse the study’s findings. Uncontrolled variables in studies of vitamin D, and of long COVID, are difficult to account for.
At the six-month follow-up, the authors of the study found no other observable differences between their matched participants than their vitamin D levels, suggesting vitamin D deficiency as a driver of long COVID symptoms.
The researchers also found that greater vitamin D deficiencies were most often associated with the neurocognitive symptoms synonymous with long COVID.
How vitamin D deficiency may lead to long COVID
While vitamin D obviously plays a role in keeping bones healthy, Dr. Giustina explained that “extra-skeletal effects of vitamin D are well-known. Among those, the positive effects on the immune system can be thought to play a role in this connection.”
Ray Marks, PhD, a lecturer of health and behavioral studies at Columbia University, told MNT that “it would be hard to refute” the study’s findings since other research is consistent with them.
Dr. Marks noted that studies indicate that vitamin D affects cognitive health, pain, obesity, and bone health, all of which, she said, “parallel long COVID and multiple chronic diseases.”
Similarly, she added that older adults having lower vitamin D levels is a common finding and that this can lead to other potentially long COVID symptoms such as cognitive disturbances, frailty, and weakness.
“The molecular mechanisms of vitamin D alone imply it is a necessary cell physiology and gene mediator with enormous organism implications if insufficient. Hence, results appear to be what one might expect, but this would need to be carefully studied.”
– Ray Marks, PhD
Dr. Marks also noted that other studies have established that people with dark skin are more likely to have vitamin D insufficiency.
For instance, the Cooper Institute reports that vitamin D deficiency affects as many as 76% of African Americans. The melanin in darker skin tones is believed to reduce the production of vitamin D.
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