The impact of physical activity and fitness on health biomarkers and oxidative stress in adults aged over 55 years = Impacto de la actividad y la condición física sobre biomarcadores de salud y estrés oxidativo en adultos mayores de 55 años

Abstract

ABSTRACT The current prevalence and the predicted increase of older population is a key health challenge in our society. Regular physical activity provides significant health benefits and physical fitness is a stronger predictor of cardiovascular and all-cause mortality than other risk factors. On the contrary, sedentary behaviour has a negative impact on health. Nutrient status affects risk-factor levels during life and may have an even greater impact in older adults. Furthermore, biomarkers are a useful tool to measure the effect of exercise such as it is essential to get deeper into the association between biomarkers and physical fitness level, and others health determinants. However, there are an increase of non-communicable diseases being a difficult task to provide effective policies and interventions. An inadequate classification of people according to physical activity and sedentary behaviours recommendations could be one the causes. The main purposes of the thesis were (1) to examine the associations between physical fitness, physical activity, sedentary behaviour, and several environmental and biochemical variables in Spanish older adults. These variables include, among others, nutritional status, health-related quality of life, vitamins and oxidative stress parameters; (2) In order to clarify the difficulty to categorize people and provide more reliable data, four different classifications have been suggested in the current thesis: (i) Combining physical activity and sedentary behaviours, (ii) According to physical fitness, (iii) Considering reference ranges from each blood marker, (iv) Combining physical fitness and blood markers, called Total Index. The current thesis is based on a cross-sectional multicentre study collecting data on 433 Spanish non-institutionalized older adults (57% females, aged over 55 years) from Madrid and Balearic Islands regions. Each classification was divided into different groups as present below: - Physical activity and sedentary behaviour classification: inactive and high sedentarism, inactive and low sedentarism, active and high sedentarism and, active and low sedentarism according to validated questionnaires. - Physical fitness classification: low, medium and high physical fitness level according to four validate physical fitness test. - Blood markers: each biomarker was categorized as being within reference range and out of the reference range considering as reference range those established by laboratories. - Total index (physical fitness & blood markers classifications): Scores of each biomarker were added together and the total score was divided into tertiles. After that, the three levels of physical fitness and three groups of biomarkers were combined together and a total index with nine different subgroups was created. The main outcomes of this thesis are: a) Males spent more time doing regular physical activity but less time walking and working at home than females. b) The proposed classification combining physical activity and sedentary behaviour is valid for males as it discriminates according to their physical fitness. c) Active and low sedentary participants obtained better results in the physical fitness tests in males and females. d) Participants in the active and low sedentary behaviour group consumed higher amounts of water and other beverages than the others groups; however, different patterns were observed according to their physical fitness level. e) Physical fitness level is related to nutrient intake, presenting greater relationships with micronutrient intake than macronutrient intake. f) There was a high inadequate intake of potassium, vitamin D and vitamin E below requirements, which was present in almost 85% of older adults, independently of their physical fitness level. g) Sex was identified as the main factor that had an effect on oxidative stress parameters. h) High lipid peroxidation measured through malondialdehyde was found in the high physical fitness group in females, whereas higher antioxidant enzyme activity measured by superoxide dismutase was observed in the high physical fitness group in males. i) There was a considerable percentage of participants who showed values out of reference range for vitamin 25(OH)D (68%) and total cholesterol (59 %), independently of physical fitness. j) More abnormal values were observed for total homocysteine, creatinine, total cholesterol, high density lipoprotein cholesterol and low density lipoprotein cholesterol in the low physical fitness group; meanwhile, less abnormal values were found for vitamin B12 and triglycerides in the low physical fitness group. k) Physical fitness index and blood index were independent between them; thus, each health marker should be measured in an independent way. l) Total index (physical fitness & blood markers) was associated with socioeconomic status, physical activity and sedentary behaviour, abdominal obesity and health-related quality of life. (m) In the model, the main predictor of the total index was education. Likewise, participants with primary school education, in the active and low sedentary group, also were categorized with less abdominal obesity. The holistic and novel approach can contribute to establish public health policies and new interventions in older adults. Key words: physical activity; physical fitness; sedentary lifestyle; biomarkers; oxidative stress; nutritional status; middle aged; elderly.