Hip fracture is one of the most representative fragility fractures, and it commonly occurs among elderly individuals. In Japan hip fractures have been increasing, with the highest proportion being in the 85–89-year-old age group for females and the 80–84-year-old age group for males [1]. In many countries, the definition of elderly is with chronological age of ≥65 years. The World Health Organization defines elderly as people aged ≥65 years. However, this definition has no clear medical or biological evidence. In Japan, although there are individual differences, many elderly people, especially those aged <75, are mentally and physically healthy and can participate in social activities. Therefore, individuals aged 65 ≥ years defined as the elderly population may not match the current situation.

To date, most studies about hip fracture target the ≥65-year-old age group. However, it is not appropriate to put all elderly patients in one bundle. The Joint Committee of Japan Gerontological Society and the Japan Geriatrics Society propose classifying people aged ≥65 years as follows [2]:

Pre-old age group: 65–74 years, old age group: 75–89 years, super-old age group: ≥ 90 years.

However, there are no studies reporting the characteristics of patients with hip fractures between these groups. Knowledge about the differences between groups is useful in postoperative management and prognostic prediction. This study aimed to identify differences in terms of the incidence of serious perioperative complications and in-hospital, 90-day, 6-month, and 1-year mortality rate according to three age groups of patients with hip fractures.