Context: Growth of the older adult population has led to an increasing interest in technology-supported aged care. However the area has some challenges such as lack of care givers and limitations in understanding the emotional, social, physical, and mental well-being needs of older adults. Furthermore, there is a gap in the understanding between younger developers and ageing people of their requirements from digital systems. Digital health can play an important role supporting older adults' well-being, emotional requirements, and social needs. Objective: We carried out a systematic review of the literature on RE for older adult digital health software. This was necessary to show the representatives of the current stage of understanding the needs of older adults in aged care digital health. Methods: Using established guidelines we developed a protocol, followed by the systematic search of eight databases. This resulted in 69 primary studies of high relevance, which were subsequently subjected to data extraction, synthesis, and reporting. Results: This systematic literature review highlights key RE processes used in digital health software for older people. It explored the key features developed for many digital solutions, utilization of technology for older user well-being and care, and the evaluations of proposed solutions. The review also identified key limitations found in existing primary studies that inspire future research opportunities. Conclusion: Our results indicate that requirements gathering and understanding have a significant variation between different studies. The differences are in the quality, depth, and techniques adopted for requirement gathering and this reason for these differences is largely due to uneven adoption of RE methods.