Both the presence and severity of depression are associated with decreased serum levels of 25-hydroxyvitamin D and increased levels of parathyroid hormone in older patients, researchers reported.
It is not yet known whether abnormal levels of 25(OH)D and PTH precede depression or are a consequence of it, they noted.
“Our findings may be of clinical relevance because the prevalence of minor depression in older persons is high (13%), and both decreased serum 25(OH)D levels and increased serum PTH levels can, in theory, be treated with higher dietary intake of vitamin D or calcium and increased exposure to daylight,” said Dr. Witte J.G. Hoogendijk and his associates at the Free University Medical Center, Amsterdam.
The investigators examined the relationship between depression and these serum markers using data from the Longitudinal Aging Study Amsterdam, an ongoing population-based study of changes in mood, autonomy, and well-being among older Dutch men and women.
In a subset of 1,282 of these subjects who were aged 65–95 years, 26 were found to have major depressive disorder and 169 were found to have minor depression.
Levels of 25(OH)D were 14% lower in people with minor depression and in people with major depression than in nondepressed people. PTH levels were 5% higher in people with minor depression and 33% higher in people with major depression than in nondepressed people, Dr. Hoogendijk and associates said (Arch. Gen. Psychiatry 2008;65:508-12).
These associations remained robust after the data were adjusted to account for several potential confounders such as gender, body mass index, smoking status, and coexisting chronic conditions. They also were not attributable to seasonal differences regarding when the assessments were done (and thus the amount of sunlight to which subjects had been recently exposed), to levels of physical activity, or to the use of antidepressants.
The importance of these results is underscored by the finding that 39% of men and 57% of women in this community-based cohort were obtaining insufficient vitamin D from their diets, including 5% of men and 7% of women who were frankly deficient in vitamin D. Only 1% of subjects were taking vitamin D or calcium supplements.
The study was supported by the Netherlands Organisation for Scientific Research.