Depression experienced by older adults is often dismissed as just another part of aging, but depression and suicide among the elderly remains a serious problem that must be addressed. New research appearing in May's Archives of General Psychiatry demonstrates how a physical condition may contribute to depression in older populations. The researchers found that individuals with low levels of vitamin D and high levels of a hormone secreted by the parathyroid gland were more likely to also have symptoms of depression.
In their study, researchers from Vrije Universiteit in Amsterdam analyzed blood samples from 1,282 seniors, aged 65 through 95. They measured levels of vitamin D and serum parathyroid hormones (PTH), while also assessing the severity of depression symptoms experienced by their subjects. 26 subjects had been diagnosed with major depressive disorder (MDD), while an additional 169 had significant symptoms of depression but did not meet the criteria for MDD. These subjects were classified as having minor depression. Analysis revealed that 38.8 percent of the men and 56.9 percent of the women had insufficient levels of vitamin D in their blood, while 4.5 percent of the men and 7.7 percent of the women had levels low enough to be considered deficient. Low levels of vitamin D can lead to a rise in PTH levels, and previous studies have examined both hyperparathyroidism and vitamin D deficiency as possible factors in depression.
Tellingly, the researchers found that higher scores on measures of depression correlated to low levels of vitamin D and high levels of PTH. Subjects with either MDD or minor depression had vitamin D levels that were 14 percent lower than those seen in subjects who were not depressed, and the disparity observed in PTH levels was even greater. Compared to non-depressed participants, those with minor depression had PTH levels that were 5 percent higher on average, while PTH levels were an average of 33 percent higher in those with MDD. These results held even when the researchers controlled for other factors that may have influenced their findings, including age, sex, weight, physical activity levels, and antidepressant use. Because exposure to sunlight affects levels of vitamin D, the researchers also considered the seasons in which the data had been collected and the urbanization of areas where the participants lived. While changes in season did not alter their results, urbanization did have a small effect. The researchers suggest that for older individuals, a reduction in outdoor activities may result in lower levels of vitamin D and hyperparathyroidism, and these conditions could then contribute to depression.
While this study indicates that in some instances treatment for a vitamin D deficiency or hyperparathyroidism may alleviate depression symptoms, further research is needed in order to clarify this relationship. As the researchers explain, their work does not indicate whether low levels of vitamin D and high levels of PTH contribute directly to depression or are merely consequences of the disorder. Depression remains a significant problem among the elderly, and researchers should continue investigating factors that may result in depressive symptoms. With an increased awareness of the disorder's prevalence among older adults along with a better understanding of how the disorder develops, we may be able to identify treatment options that will be most effective for this population.
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