Which factor is NOT typically a risk for increased infection susceptibility in older adults?

An active immune system is typically not a risk factor for increased susceptibility to infections in older adults. In fact, many older adults experience a decline in immune function, a process known as immunosenescence. This leads to a diminished ability to respond effectively to pathogens, making them more vulnerable to infections.

In contrast, poor nutrition, chronic illness, and immobility are well-documented risk factors that can compromise the immune system and overall health of older adults. Poor nutrition can reduce the body’s ability to mount an effective immune response, chronic illnesses can tax the immune system's resources and lead to increased susceptibility to infections, and immobility can contribute to complications such as pressure ulcers and respiratory issues, further raising the risk of infection. Thus, the presence of an active immune system would actually indicate a healthier state in the context of infection susceptibility.