One survey (lindau et al., 2007) found that the most common barriers to sexual activity in adults aged 57 to 85 were

The correct answer is health problems or an individual lacks a partner.

When an adult, who is nearing an older age faces health problems may be unable to perform in sexual activity, since their body will feel weaker than usual rather than before. While other old adults, who are healthy, yet cannot perform sexual activity is because they lack a partner, because older adults sometimes experience the loss of a partner in their old age, due to health problems or accidents.