Table 2.

Studies concerning the protective mechanism of physical activity towards aging

Study	Type of study	Number of subjects examined	Results
Tan et al. [37]	Case–control study (pilot randomized controlled evaluation)	113	Older adults who were engaging in volunteering showed an increase in their physical activity level
Sofi et al. [30]	Systematic meta-analysis of prospective studies	33,816	Physical activity of all levels showed a protective effect on the occurrence of cognitive decline
ATTICA study; Kollia et al. [27]	Observational population study	853	Higher Healthy Aging Index (which included physical activity) was associated with lower 10-year CVD risk
Lindsay-Smith et al. [35]	Observational population study	28	Group-based social and physical activities programs for older people may improve their well-being and prevent loneliness
Xu et al. [29]	Observational population study	613	Physical activity was associated with a reduced risk of developing metabolic syndrome in the participants with the highest levels of physical activity
de Oliveira et al. [32]	Observational population study	200	There was a correlation between low levels of physical activity and symptoms of anxiety and depression in older people
Steltenpohl et al. [34]	Observational population study	39	Older adults were more likely to prefer to exercise with others, rather than alone
Liu et al. [31]	Meta-analysis of randomized controlled trials	1039	In the elderly with cognitive decline, exercise and nutrition interventions showed a positive effect on global cognitive function
Barnes et al. [33]	Observational population study	6994	Loneliness and social isolation in older people was associated with lower quality of life and higher medical costs