Sex differences in the associations of physical fitness, physical activity, sedentarism, and sleep behaviour with oxidative stress in older adults

Resumen

Currently, the elderly population is expanding due to an unprecedented increase in longevity. Unfortunately, this trend in the rising ageing population comes with the consequences of the augmentation of physiological decline leading to metabolic diseases or oxidative stress. Oxidative stress has been defined as a pathophysiological state characterised by an imbalance between the excessive production of oxidants (such as homocysteine, HCY) and the inability of the total antioxidant capacity (TAC) of the body to cope with them. When this condition occurs an accumulation of oxidatively damaged macromolecules appears, leading to the loss of function of these macromolecules which contributes to the appearance of no communicable diseases such as cardiovascular diseases or musculoskeletal diseases. Consequently, it is needed to know how different factors can help to maintain healthy ageing in older adults. Maintaining good physical fitness, adequate levels of physical activity (PA), and healthy sleep behaviour have been shown to reduce the possible mechanisms of ageing such as oxidative stress. However, to our knowledge, it is still unknown whether these factors can differently affect the oxidative stress of older adults depending on sex since most of the studies analysed the data combined. Therefore, the general aim of this International Doctoral Thesis was to study the sex-specific associations of anthropometry, body composition, physical fitness, PA, sedentarism and sleep behaviour with oxidative stress levels, in a sample of Spanish older adults. This International Doctoral Thesis includes cross-sectional data from the INTERMAE project. A total of 76 participants (38 women, 68.8 ± 3.0 years old) recruited through the public health care centers of the province of Cádiz were included. Blood samples were obtained from the participants to obtain the plasma levels of TAC and serum levels of HCY. Then participants completed different measurements including body composition, physical fitness through different physical batteries and cardiorespiratory fitness test (CRF), nutritional evaluation, and questionnaires about their PA and sleep manners. In addition to this, participants wore an accelerometer for at least 7 days to estimate their sedentary (SB), PA and sleep behaviours. The main findings of this International Doctoral Thesis are i) there are sex differences in basal oxidative stress markers in Spanish older adults, regardless of their nutritional intake., ii) Higher body mass index and thigh perimeter in women and higher fat-free mass in men are associated with higher levels of HCY. iii) In older women a faster gait speed is associated with higher levels of TAC. Better upper body strength, flexibility and gait agility are associated with lower levels of HCY. Higher CRF is associated with lower levels of HCY in both sexes. (Study 1); iv) PA levels seem to be more relevant to older adults? oxidative stress than SB, with moderate to vigorous PA being associated with increasing TAC and light PA with decreasing HCY in both sexes (Study 2); v) Sleep disorders were associated with oxidative stress in older adults, with more time awake during the night associated with a decreased TAC in women and a higher sleep latency being associated with higher levels of HCY in men (Study 3). The findings of the present International Doctoral Thesis show that there are sex-specific associations of anthropometric, body composition, physical fitness, PA and sleep behaviour with oxidative stress in older adults.