Inverse Relationship Between Depressive Symptoms and Arterial Blood Pressure in Community‐Dwelling Oldest‐Old B razilians

In Brazil, the average life expectancy for people who are 80 years old is 9.6 years.1 As in other middle-income countries, the oldest-old (≥80) Brazilians are the fastest-growing age group of elderly adults.1 Hypertension and depression are two common health problems in elderly adults. Hypertension during middle age is an obvious cause of stroke, vascular dementia, myocardial infarction, renal failure, and retinopathy,2 all of which are well-known causes of depression.3 Low blood pressure (BP) in elderly adults has been associated with systolic heart failure and chronic diseases associated with malnutrition, such as cancer and dementia.4 Some studies have found an association between low BP and frailty in the general elderly population, suggesting that BP might be lower with pathological aging,5 although the relationship between BP and depression is controversial.6-10 Longitudinal studies have had inconsistency regarding the association between BP and depressive symptoms in the general elderly population, possibly indicating the existence of confounding factors between these variables.6-8 Some have reported that baseline low BP predicts depressive symptoms at follow-up but that the inverse was not true.7, 8 Another study has found the opposite results—that depression is associated with lower BP at follow-up.6 Another study found that hypertension was associated with depressive symptoms at follow-up.9 Differences in study design, population age distribution, and health status may have contributed to these divergent findings in different studies.6-10 Many of the aforementioned studies did not include a representative proportion of very elderly people in their sample, and none evaluated exclusively the oldest old. The relationship between BP and depressive symptoms was investigated in a community-based Brazilian population aged 80 and older. The total probabilistic sample of this cross-sectional study consisted of 272 older people living in two Brazilian cities: 155 in Ribeirão Preto (São Paulo State) and 117 in Caxias do Sul (Rio Grande do Sul State). Data were collected in home interviews and encompassed sociodemographic characteristics, mean (from two independent measures) systolic and diastolic BP, and the short-form version (15 items) of the Geriatric Depression Scale (GDS). The Ethical Committee of the Ribeirão Preto School of Nursing (São Paulo University) approved this study, and data were analyzed using SPSS version 18.0 (SPSS, Inc., Chicago, IL). Mean age was 84.7 ± 4.2, 67.6% of participants were female, and mean years of schooling was 3.7 ± 3.8 years. An inverse linear regression line best fit the relationship between diastolic BP and GDS score (coefficient of determination (r²) = 0.031, P = 0.004), whereas a quadratic regression curve best represented the relationship between systolic BP and GDS score (r² = 0.036, P = .009) (Figure 1). Both associations remained statistically significant even after controlling for age, sex, and schooling (P < .01 for both). Whether antihypertensive drugs can cause depressive symptoms remains controversial,7 although, some antidepressants cause postural hypotension.2 These medications might partially mediate the association between low BP and depressive symptoms. In the current study, whether individuals were taking antihypertensive or antidepressant drugs was not evaluated, but other studies have reported that adjusting for the use of antihypertensive and antidepressant drugs did not alter the association between BP and depression.7-10 Several possible mechanisms for low BP causing depression have been hypothesized.10 Systolic heart failure may decrease cerebral blood flow in older individuals with impaired cerebral autoregulation,10 and malnutrition associated with several chronic degenerative diseases may decrease BP and contribute to depression.7 Moreover, common hierarchically superior mechanisms, such as those involved in the pathophysiology of frailty and brain degeneration in dementia, might cause low BP and depression. In the current study, a formal evaluation was not performed to diagnose frailty or dementia. It is not possible to infer causality from this cross-sectional study, but health professionals should be aware of the possible relationship between low BP and depression when caring for older people. This information might be helpful when considering the not-uncommon finding of depressive symptomatology associated with rapid BP control in older people. Complexity increases with aging. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. This study was funded by the Fundação de Amparo à Pesquisa do Estado de São Paulo. Author Contributions: IR: study concept, analysis of data, preparation of manuscript. LR, RPR, and JCN: literature review, preparation of manuscript. MRC: interpretation of data, critical review of manuscript. All authors made substantial intellectual contributions to this manuscript. Sponsor's Role: None.