Final answer:
Muscle strength is the best indicator of health and vitality in the elderly as it reflects their physical function and ability to perform daily activities.
Step-by-step explanation:
The best indicator of health and vitality in the elderly is muscle strength. While blood pressure, cholesterol level, and body mass index (BMI) are important measures, muscle strength is particularly significant because it reflects physical function and ability to perform activities of daily living. Muscle strength is crucial in maintaining mobility, balance, and independence in older adults. It directly affects the ability to carry out tasks such as walking, climbing stairs, and lifting objects.