Senescence is a natural life process associated with increased risk of non-communicable diseases, as hypertension. In fact, there is a growing prevalence of hypertension with increasing age.1 This is worrying, since it is expected that the world population over 60 years old will be approximately two billion in the next decades2 and the prevalence of hypertension could reach up to 80% among elders.3

Hypertension is recognized as a multifactorial clinical condition, with lifestyle- related factors, such as smoking, high sodium intake, sedentary lifestyle, among others, widely associated with this condition. However, recent studies have pointed to a close relationship between hypertension and depression,4 which becomes even more worrying when considering the elderly people, due to the known association between depression and aging.5

Depressive disorder is common among the elderly; it is a multi-causal condition, whose etiology may vary from depressive disorders, observed in young adults, to those associated with chronic age-related processes (cardiovascular, inflammatory, endocrine, autoimmune processes), continuous use of some medications, psychological adversity, and cognitive deficits.6 Approximately 10% of individuals over 60 years old require therapeutic intervention for depressive disorder, and the prevalence of depression may be greater than 40% among elders living in geriatric institutions.7

Changes in autonomic nervous system control, characterized by worse vagal control and increased heart rate, are observed in depressive subjects and are pointed out as factors that may explain the predisposition to hypertension.8 In addition, it is known that, among elders, the association between depression and hypertension seems to be influenced by obesity.9

The study by Long et al.,9 raises an important perspective in the understanding of the relationship between depression and hypertension among elders. In fact, Meng al.,10 had already reported that variables such as gender, race, smoking, physical activity level, obesity / body mass index (BMI), DM and other psychological factors are potentially confounding variables in the relationship between depression and hypertension. In this context, the present study aimed to analyze the association between depression and hypertension in community-dwelling elders, as well as to analyze the influence of confounding variables that are potentially capable to influence this association.

In the study population, the prevalence of depressive state was 14% and of hypertension was 59%. Hypertensive elderly subjects had significantly higher BMI compared with normotensive subjects (27.20 ± 5.75 kg/m² vs, 23.80 ± 7.13 kg/m², p < 0.05. Age was not different between hypertensive and normotensive elders (72.00 ± 11.00 years old vs. 71.00 ± 13.00 years old, respectively, p > 0.05). Hypertension was significantly associated with DM (p < 0.05), while the variables sex, race, smoking habits, and physical activity level were not significantly associated (p > 0.05). Table 1 shows the association of categorical variables (sex, race, smoking habits, DM and physical activity level) with hypertension.

Depressive elders were significantly older than non-depressive elders (76.00 ± 11.50 vs. 71.00 ± 11.00 years old, p < 0.05). Regarding BMI, there was no significant difference between depressive and non-depressive elders (25.20 ± 6.95 kg/m² vs. 25.60 ± 7.33 kg/m², respectively, p > 0.05). Depression was significantly associated with physical activity level (p < 0.05), but not with the variables sex, race, smoking habit, and diabetes mellitus were not significantly associated (p > 0.05). Table 1 shows the association of categorical variables (sex, race, smoking habits, diabetes mellitus and physical activity) with hypertension.

Since the variables DM, BMI, and physical activity level were associated with hypertension and depression, logistic regression analysis was performed, with and without adjustments for the cited variables. Table 3 shows the regression coefficient, and the odds ratio (OR) and its 95% confidence interval of the variables included in the adjusted and unadjusted logistic regression analysis. It is possible that the association between hypertension and depression was directly influenced by BMI, and physical activity level, while the analysis adjusted for all the variables (DM, BMI and physical activity level) together also confirmed the significant influence of these variables on the relationship between depression and hypertension in community-dwelling elders.

The present study aimed to analyze the association between depression and hypertension in community-dwelling elders, and to analyze the influence of potential confounding variables. Our results showed that the association between depression and hypertension was significantly influenced by BMI, physical activity level and DM.

In fact, no significant association was found between depression and hypertension (OR [95%CI] = 2.28 [0.98 - 5.32]; p = 0.06) when analyzed without adjustment variables. However, after adjustment for the variables BMI (OR [CI95%] = 2.66 [1.04 - 6.79], p = 0.04) and physical activity level (OR [CI95%] = 3.41 [1.31 - 8.85], p = 0.01) a significant association was found between depression and hypertension in the study population. The analysis adjusted for BMI, physical activity level and DM together also influenced significantly the association between depression and hypertension (OR [95%CI] = 3.08 [1.12 - 8.46]; p = 0.03).

In our study, DM was significantly associated with hypertension, but not with depression, which may explain the lack of influence of the adjustment for DM on the association between hypertension and depression. Previous studies have shown that DM is common among depressed people;16^,17 in fact, in our study, 31.3% of depressed elderly people were diabetic, whereas this prevalence was only 18.8% among non-depressed elderly people. However, no significant difference was achieved. Despite this, the considerably higher prevalence of diabetic elderly among depressive and (statistically significant) hypertensive elders justifies the maintenance of this intervening variable (i.e., DM) in the regression model adjusted for DM, BMI and level of physical activity.

The close association of obesity with depression18^,19 and hypertension20^,21 explains the strong influence of this variable on the relationship between depression and hypertension. Follow-up studies have corroborated such relationship, since the presence of obesity increases by 1.55 times the odds to develop depression, just as depression increases 1.58 times the odds to develop obesity.19^-22 Therefore, a higher cardiovascular risk comes from the association of these conditions, i.e., obesity and depression.18^,23

The adoption of a physically active lifestyle has been pointed out as an effective behavioral intervention to treat depression symptoms.24^,25 Josefsson et al.,26 in a systematic review with meta-analysis on this issue, concluded that the use of exercise as an intervention generates positive results in mild-to-moderate depression. Blake et al.27 stated that physical activity programs can achieve positive results in the treatment of depressive symptoms in the elderly.

The recent study of Holmquist et al.,28 broadens the basis of these findings. In the cited study, the authors evaluated the association of depression with several lifestyle-related variables, previous illnesses and physical performance in the elderly. It was observed that depressed elders (GDS ≥ 5 points) were predominantly obese, diabetic, and physically less active (or had worse physical performance). In fact, these same variables may be associated with hypertension, and thus can influence the association between hypertension and depression. In this sense, two aspects are relevant: 1) the identification of depressive, obese, diabetic and insufficiently active elderly subjects can guide the screening of those prone to hypertension, since this set of factors among elders increases in 3.08 (1.12 - 8.46) times the odds of being hypertensive; 2) all the studied factors associated with hypertension and depression here are amenable to intervention; thus, as proposed by Blake et al.,27 preventive strategies focused on physical activity could represent an excellent strategy from the point of view of cost-effectiveness to prevent hypertension in depressed elderly people, since the level of physical activity increases 3.41 (1.31 - 8.85) times the odds of a depressed elderly subject being hypertensive.

Our results showed that BMI, DM and physical activity level influence the association between hypertension and depression in community-dwelling elders. DM affects the association between depression and hypertension when combined to physical activity and BMI. In addition, the level of physical activity seems to be the main influencing factor of this relationship. This promotes positive perspectives regarding therapeutic interventions, since, unlike drug interventions, the adoption of a physically active lifestyle is an excellent, cost-effective intervention for both hypertension and depression.