Fitness, body composition, and depressive symptoms in healthy and depressed adults and older adults

Resumen

Depression affects around 300 million people worldwide, and it is expected that will be the world's leading disease burden by 2030. Indeed, 13% of the Spanish population aged 15 and over presented depressive symptoms, with a higher impact on women. The frequency of symptoms rises more steeply with aging affecting approximately 24% of older adults. Suffering from depressive symptoms or diagnosed depression is related to other pathologies and health problems. Thus, it is crucial to find strategies to mitigate and protect against this problem in adults and older adults. On the other hand, health-related physical fitness has been demonstrated scientifically to have psychological benefits and, it could be an effective and side-effect-free method of preventing depressive symptoms. In consequence, determining the relation of each component of fitness and different indicators of body composition with depressive symptoms may have an impact on public health and future interventions focused on improving fitness and body composition since they are modifiable risk factors. Moreover, the research on the population with a diagnosis of depression is even scarcer, so it is a priority to know the relationship in this case as well. Therefore, the general aim of this International Doctoral Thesis was to investigate the relationship of fitness components and body composition with depressive symptoms in healthy and depressed adults and older adults. To achieve this objective, three studies have been conducted, a systematic review (Study I) and, cross-sectional data from the INTERMAE (Study II) and SONRIE (Study III) studies. In Study I, systematic searches were conducted in PubMed and Web of Science. Longitudinal and cross-sectional studies were included if they measured at least one fitness component and depressive symptoms indicator in healthy and/or depressed adults or older adults (18 years and over). In Study II, ninety-two older adults (42 females, 68 ± 3 years) were included. Fitness components were measured by Senior Fitness Test (SFT), Short Physical Performance Scale (SPPB), gait speed, handgrip, and cardiopulmonary exercise tests (CPET). Body composition was assessed by body mass index (BMI), fat mass and muscle mass percentages obtained using a multifrequency bioimpedance, and waist and hip circumferences. Depressive symptoms were collected by Geriatric Depression Scale-15 (GDS-15). In Study III, eighty-two adults with a diagnosis of mild to moderate depression (69 females, 49 ± 10 years) were included. Fitness components were measured by SFT, SPPB, gait speed, unipedal stance, standing long jump and handgrip tests. Body composition was assessed similarly to Study II. Depressive symptoms were collected by Beck Depression Inventory II (BDI-II). The main findings of this International Doctoral Thesis are i) Cardiorespiratory fitness (CRF), strength, and gait speed were inversely related to depressive symptoms longitudinally. ii) All fitness components except flexibility and other gait parameters were inversely related to depressive symptoms cross-sectionally in healthy adults and older adults. iii) There is no evidence regarding the specific population with diagnosed depression. (Study I); iv) Higher levels of fitness, notably gait speed, and muscle strength and lower fatness seem to contribute to having fewer depressive symptoms in older adults. In addition, higher performances in gait speed, agility, upper-limb muscular strength and CRF, as well as, more appropriate fat and muscle levels, appear to have a beneficial impact, individually, on these symptoms. (Study II); v) Better perceived fitness and higher balance performance may have a protective effect against depressive symptoms in adults with depression. Additionally, a larger hip circumference may be related to more depressive symptoms. (Study III); Older adults and adults with depression identified as low-fit and high-fat might have increased odds of higher depressive symptoms compared to their high-fit and low-fat peers. (Study II and Study III). The findings of the present International Doctoral Thesis show that all components of fitness and body composition, except flexibility, appear to have a beneficial impact on depressive symptoms in healthy adults and older adults. However, for the specific population with depression, only balance, hip circumference and self-reported fitness are related. In both populations, those with low fit and high fat profile could further increase depressive symptoms.