The Importance of Active Engagement
People learn continually through active engagement in their environments, and research has demonstrated that engaging in some activities promotes healthy aging, including performance in cognitive tasks.
How People Learn II, pg. 220
Cognitive Growth through Interactivity
It has been demonstrated that learning through active engagement, involving students in activities that require working with and reflecting on the material, helps to promote a healthy lifestyle. Certain activities can help even with cognitive performance, but certain activities are more beneficial than others. A reduction in risk of cognitive impairment later in life has been shown to associate with physical activity.
Beneficial Activities
Work activities, the functions and duties one performs as part of their job, are important in reducing the risk of cognitive impairment after retirement. This is especially the case when the work itself is demanding and difficult. Mentoring and supervising, for example, are correlated to an increase in verbal ability, as compared to people who perform less-complex work. Social and intellectual activities that require interpersonal interactions are also associated with higher cognitive ability
Interestingly, cognitive decline has been observed in people whose jobs required physical labor or visual demands.
Physical Activities
Physical activities may lead to cognitive complications later in life. These include strength-based exercises, like lifting and pulling, and also visually-demanding exercises. However, because research has been conducted showing that physical activity can enhance cognitive abilities, there is some confusion as to the actual benefits of physical activity.
While no conclusive research has been performed, the current theory suggests that a balance between physical and mental activity seems to best preserve cognition later in life. It is also theorized that physically-demanding jobs do not allow for the kinds of labor or activity which does promote cognitive growth, such as aerobics.
Additional Research
Most research on physical/mental activities and its relationship to aging demonstrate a observational or correlative connection. In the last 15 years, other research has been conducted which show a causal relationship between activities and desired cognitive outcomes. Team competitions and problem-solving, as example activities, may benefit one's reasoning and episodic memory.
There has been no definitive research on the topic, but it seems likely that a balance of cognitive demands and physical exercise may preserve abilities.