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Low vitamin D tied to depression in older people

Older men and women with lower levels of vitamin D in their blood are more prone to become depressed over time, new research shows.

Many studies have been published recently on the potential health benefits of vitamin D, and the potential risks of deficiency. Low vitamin D levels have been linked to heart disease, stroke, high blood pressure, and more severe asthma.

In older people, insufficient vitamin D is quite common, and has been linked to fractures, worse physical function, greater frailty, and a wide variety of chronic illness.

In the current study, Dr. Luigi Ferrucci of the National Institute on Aging in Baltimore and colleagues looked at whether low vitamin D levels and depression in older people might be related.

They followed 531 women and 423 men 65 and older who were participating in the InCHIANTI Study, a long-term investigation of factors associated with loss of mobility in aging people, over six years.

At the study's outset, 42 percent of the women and 18 percent of the men were depressed, while three-quarters of the women and half of the men had levels of vitamin D below 50 nanomoles per liter, which is generally considered insufficient.

Seventy-two percent of the depressed people and 60 percent of the non-depressed people had vitamin D insufficiency - the level above deficiency -- the researchers found. Women with vitamin D insufficiency showed a worse decline in mood at three and six years into the study; their scores on a standardized test measuring depressive symptoms increased more at three and six years compared to the scores for women who had adequate vitamin D. This increase could have tipped the scale into a diagnosis of depression for some people.

Women with low vitamin D who weren't depressed at the beginning of the study were also twice as likely to become depressed over the following six years as the women who had sufficient levels of the nutrient. While similar patterns were seen for men, the association wasn't as strong, and in some cases could have been due to chance, according to the researchers.

The study does not prove that low vitamin D levels cause depression, the authors note; people with low levels of the nutrient might have other characteristics that predispose them to the blues.

Still, they suggest that preventing “vitamin D deficiency in the elderly may become in the future a strategy to prevent the development of depressive mood in the elderly and avoid its deleterious consequences on health. In addition, normalization of vitamin D levels may be part of any depression treatment plans in older patients.”

Vitamin D, produced by the body when skin is exposed to sunlight, is also found in certain foods such as oily fish. It helps cells absorb calcium and is important for bone health.

However, the authors conclude, before any strategies to boost vitamin D can be adopted they must be tested in larger and more rigorously designed trials.

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