A major factor contributing to the aging population's healthcare needs is:

The correct answer focuses on increased lifespan, which is a significant factor impacting the healthcare needs of the aging population. As individuals live longer, they often face more complex health challenges that require ongoing medical attention and support. This extended lifespan can lead to an increased prevalence of chronic diseases and conditions associated with aging, such as heart disease, diabetes, and dementia, which demand more healthcare resources and attention.

The impact of increased lifespan contributes to the need for more comprehensive geriatric care, preventive services, and long-term support. Healthcare systems must adapt to address the unique needs of older adults, including the management of multiple comorbidities and the provision of specialized care. This growing demographic shift places substantial pressure on healthcare systems to ensure quality care for an increasingly elderly population.

Other options, while related, do not as directly capture the primary driver of the heightened healthcare needs in aging. For instance, a declining birth rate relates more to population dynamics than to the immediate healthcare requirements of those already aging. Decreased healthcare options and lower rates of chronic illness are not accurate reflections of the current realities faced by an aging population, given that many older adults do experience chronic illnesses that necessitate significant healthcare resources.