Trends in incidence of intracerebral hemorrhage and its bleeding sites from 1985 to 2017 in Japanese rural communities.

Introduction: Evaluating long-term trends for the incidence of intracerebral hemorrhage is a priority for primary prevention. It is also important to assess the trends in the proportions of bleeding sites because the pathogenesis, prognosis, and operative procedures differ among them.

Methods: A prospective community-wide stroke registry in two rural Japanese communities (Ikawa Town and Kyowa Town, with populations of approximately 5000 and 15,000, respectively) was conducted. The age-adjusted incidence of intracerebral hemorrhage from 1985 to 2017 was calculated by the direct method using the World Standard Population. The proportions of intracerebral hemorrhage by bleeding sites (putamen, thalamus, lobes, cerebellum, and brainstem) based on neuroimaging were calculated in each of the following three periods: 1985-1995, 1996-2006, and 2007-2017.

Results: During the study period, 383 intracerebral hemorrhage events as first-ever strokes were registered. The age-adjusted incidence declined over time by 33%, with a large reduction between 1985-1989 and 1990-1994, but the magnitude of the decline has diminished since the 1990s. The proportions of bleeding sites were 37%, 29%, and 31% for putamen in 1985-1995, 1996-2006, and 2007-2017, respectively; the corresponding proportions were 24%, 35%, and 18% for thalamus; 10%, 10%, and 21% for lobes; 2%, 8%, and 12% for cerebellum; and 8%, 6%, and 5% for brain stem.

Conclusion: The age-adjusted incidence declined by 33% from the 1990s with a large reduction in the early 1990s in Japanese rural communities. Among intracerebral hemorrhages, the proportion of bleeding sites decreased for the putamen, thalamus, and brain stem, and increased for lobes and the cerebellum.