Background Bicycle riding is a popular leisure activity worldwide, even to older population. On the other hand, it requires delicate sense of balance and quickness of reaction to avoid accidents. Despite the popularity of bicycle, elders need to cautious when riding, especially at night.

Purpose The objective of this study is to investigate effect of time of day on bike accident injuries on old aged population.

Method Data from Emergency department based In-depth Injury Surveillance Data collected by Korean CDC were analyzed for patients 65 years or older hospitalized following bike accident during driving. Data from 2013 to 2016 was used in analysis with excluding those without hospital outcome or information on injury incident time. Main exposure was incident time which was categorized in to 4 groups, day time (9 am to 6 pm), dawn (6 am to 9 am), evening (6 pm to 9 pm) and night (9 pm to 6 am). Main outcome was hospitalization including hospital death. Secondary outcome was non-fatal injury excluding hospital deaths from hospitalized patients.

Result Total 3174 patients visited ED by bike accident. Among them, 1815 accidents happened at day time, 560 at evening, 476 at dawn and 302 at night. From 302 night time accidents, 132 (43.7%) were admitted and from 1815 day time accidents 665 (36.6%) patients were admitted. The odds ratio of night time accident for hospitalization in old age bike drivers were 1.4 (95% CI 1.09–1.79) compared to day time accidents. The odds of night time accidents for non-fatal injuries were 1.40 (95% CI 1.09–1.80).

Conclusion Nigh time bike driving is more hazardous for old age population. Community based preventions as well as individual preventive strategy to prevent injuries during night time bike riding need to be applied. Further research is needed.