Fatty acid composition related to depression in older individuals - Geriatric Nutrition

Nutrition Research Newsletter, August, 2003

The long-chain polyunsaturated fatty acids (PUFAs) are divided into two main families: n-3 and n-6. The specific concentration of these fatty acids in the blood reflect dietary intakes. As Western societies have changed their eating patterns over the past decade, they are believed to have altered the ratio of n-6 to n-3 PUFAs. The increases in ischemic heart disease and depressive disorders have been hypothesized to be reflective of these dietary changes and may be directly related to the ratio of PUFAs.

Different mechanisms may be behind this relationship. Fatty acid composition determines the biophysical properties of neuronal membranes and influences neurotransmission. Higher n-3 PUFA concentrations lead to higher membrane fluidity, which in turn increases serotonin transport. Another mechanism may be that dietary intake of n-3 PUFAs decreases the risk of atherosclerosis and increased n-6 PUFAs result in an overproduction of prostacyclins and inflammatory markers. As both inflammation and atherosclerosis have been associated with depression, this could link fatty acids and depression. However, now it is unknown whether fatty acid composition affects mood in the general, community-dwelling population.

A study was performed to investigate the relation between the fatty acid composition of plasma phospholipids and depressive disorders in elderly person, with control for a number of demographic and biological variables. The study was based on the Rotterdam Study, an ongoing, population-based cohort study in which all in habitants of a suburb of Rotterdam who were = 55 years of age in 1990-1993 were invited to participate. A total of 7983 men and women participated in the study. During the third survey, assessment of depressive symptoms was added to the study protocol. The assessment included a home interview and a visit to the research center. Investigators compared fatty acid composition between all subjects with depressive symptoms and randomly selected reference subjects.

Depressive disorders were assessed using a two-step procedure. First, subjects completed the Dutch version of the original Center for Epidemiologic Studies Depression scale (CES-D) during the home interview. Second, those who screened positive had a psychiatric work-up with the Dutch version of the Present State Examination (PSE-10), a semi-structured psychiatric interview. Psychiatric disorders were classified according to criteria from the Diagnostic and Statistical Manual of Mental Disorder, 4th edition (DSM-IV). A sample of 461 participants, aged from 61 to 101 years served as the reference group. Psychiatric disorders and duration of symptoms were defined in 250 participants. Psychiatric work-up revealed that 106 subjects had a depressive disorder and the remaining 144 subjects were diagnosed as having either an anxiety disorder or another psychiatric disorder. They were randomly selected from participants in the Rotterdam Study who screened negative for depression.

Following an overnight fast, blood was collected and the concentrations of fatty acids originating from the phospholipid fraction of plasma were measured. The variables that were considered as possible confounding variables included age, sex, level of education, history of stroke, cognitive function as measured by the Mini Mental State Examination, disabilities in the activities of daily living, and the cardiovascular disease risk factors such as cigarette smoking, blood pressure, and serum total and HDL cholesterol. The inflammation marker C-reactive protein (CRP) was also measured.

Subjects with depressive disorders were found to have a higher ratio of n-6 to n-3 PUFAs. However, differences in individual PUFAs were mostly small. Depressed subjects with normal CRP concentrations had a substantially altered fatty acid composition; percentages of n-3 PUFAs and ratios of n-6 to n-3 PUFAs were significantly lower and higher, respectively, in subjects with depressive disorders than in control subjects [5.2% compared with 5.9% (P = 0.02) and 7.2 compared with 6.6 (P = 0.01), respectively]. This relation was not due to atherosclerosis.

It appears that in community-dwelling older individuals, fatty acid composition is related to depression. As this relationship did not seem to be due to inflammation, atherosclerosis, or possible confounders, it suggests a direct effect of fatty acid composition on mood.

H. Tiemeier, H. Ruud van Tuijl, A. Hofmal, et al. Plasma fatty acid composition and depression are associated in the elderly: the Rotterdam Study. Am J Clin Nutr; 78:40-46 (July, 2003). [Correspondence: MMB Breteler, Department of Epidemiology and Biostatistics, Erasmus Medical Centre, PO Box 1738, 3000 DR Rotterdam, Netherlands. E-mail: breteler@epib.fgg.eur.nl].