Nobuyoshi Tomioka

Higher stroke incidence in the spring season regardless of conventional risk factors: Takashima Stroke Registry, Japan, 1988-2001.

Background and Purpose— Seasonal variation in stroke incidence was examined using 14-year stroke registration data in a Japanese population. We also examined if this variation was modified by conventional stroke risk factors hypertension, diabetes mellitus, drinking, and smoking. Methods— Data were obtained from the Takashima Stroke Registry, which covers a stable population of ≈55 000 in Takashima County in central Japan. There were 1665 (men, 893; women, 772) registered first-ever stroke cases during 1988 to 2001. The average age of stroke onset for men and women patients was 69.4 and 74.2 years, respectively. Incidence rates (per 100 000 person-years) and 95% CI were calculated by gender, age, and stroke subtype for winter, spring, summer, and autumn. After stratifying patients by their risk factor history, the OR (with 95% CI) of having a stroke in autumn, winter, and spring were calculated, with summer serving as a reference. Results— Among the seasons, stroke incidence per 100 000 person-years was highest in the spring (231.3; 95% CI, 211.1 to 251.5). Spring incidence was highest in both men (240.8; 95% CI, 211.5 to 270.2) and women (222.1; 95% CI, 194.4 to 249.9), and in subjects younger than 65 years (72.6; 95% CI, 60.0 to 85.3) and 65 years or older (875.9; 95% CI, 787.5 to 964.3). Among stroke subtypes, spring incidence was highest for cerebral infarction (154.7; 95% CI, 138.2 to 171.2) and cerebral hemorrhage (53.7; 95% CI, 44.0 to 63.4). The spring excess in stroke incidence was observed regardless of the presence or absence of the risk factor histories. Conclusions— Stroke incidence appears to be highest in the spring among a Japanese population regardless of conventional risk factor history. Factors that explain this excess need further investigation.

Trend of Stroke Incidence in a Japanese Population: Takashima Stroke Registry, 1990-2001:

Background In Japan, stroke mortality and incidence started to decline during the 1960s. The recent unfavourably diverging trends in risk factors make it uncertain whether the decline will continue. Few comprehensive stroke registries of long research duration exist in Japan to illustrate the trends in stroke incidence. Objective We examined 12-year stroke registration data to evaluate the current trend in a Japanese population. Methods Data were obtained from the Takashima Stroke Registry, covering approximately 55000 residents of Takashima County in central Japan. We calculated the age-adjusted stroke incidence rates (/100 000 person-years) and 95% confidence intervals for 1990–1992, 1993–1995, 1996–1998, and 1999–2001. We applied the direct method to adjust for the age distribution among the four periods. The incidence time trend was determined by calculating the average annual change across the study years using negative binomial regression analysis. Results There were 1453 (men: 771 and women: 682) registered first-ever stroke cases during 1990–2001. The diagnosis was established by neuro-imaging in 93·6% of the cases. The average age was 69·4 years in men and 74·2 years in women. The age-adjusted incidence rates of stroke across the four observation periods were 143·1 (confidence interval: 127·4-158·8) in 1990–1992, 147·4 (confidence interval: 131·9–162·8) in 1993–1995, 120·4 (confidence interval: 106·7–134·0) in 1996–1998, and 122·9 (confidence interval: 109·6–136·2) in 1999–2001. The stroke incidence across the study years showed an insignificant time trend, with an average annual change of −0·33% (confidence interval: −2·44 to 1·78) per year. Similar trends were observed for both men and women and stroke subtypes. Conclusions The previously reported declining trend in stroke incidence may have levelled off or slowed down considerably in the Japanese population.

Seasonal Pattern of Incidence and Case Fatality of Acute Myocardial Infarction in a Japanese Population (from the Takashima AMI Registry, 1988 to 2003)

We examined the seasonal variations in the incidence and case fatality of acute myocardial infarction (AMI) in a geographically defined population using 16-year AMI registration data. It remains unclear whether the incident events of AMI display any seasonal variation. Documentation of such a pattern may foster investigation for understanding the potential mechanisms responsible for these effects and may provide novel avenues for prevention of AMI. Data were obtained from the Takashima AMI Registry, which covers an entire community of approximately 55,000 in central Japan. There were 335 definite cases of AMI during 1988 to 2003 (217 men, 118 women). Of these, there were 96 fatal cases (53 men, 43 women) within 28 days of onset. Incidence rates (per 100,000 person-years) and case fatality rates with 95% confidence intervals (CI) were calculated across seasons. Poisson regression analysis was used to calculate the incidence rate, and case fatality ratios adjusted for age and gender. The AMI incidence rate was higher in winter (44.9, 95% CI 35.9 to 53.9) and spring (44.1, 95% CI 35.3 to 52.9) than the other seasons. After adjustment for age and gender, AMI risk was 1.4 (95% CI 1.03 to 1.9) times higher in winter and was 1.4 (95% CI 1.01 to 1.9) times higher in spring than summer. The 28-day AMI case fatality rate was also higher in winter (34.4%, 95% CI 24.9 to 43.9) and spring (32.3%, 95% CI 22.9 to 41.7). Age- and gender-adjusted fatality risk was 2.4 (95% CI 1.2 to 4.9) times higher in winter and 2.3 (95% CI 1.1 to 4.6) times higher in spring than summer. In conclusion, higher AMI incidence and case fatality rates were observed in winter and spring in a Japanese population.

Stroke case fatality shows seasonal variation regardless of risk factor status in a Japanese population: 15-year results from the Takashima Stroke Registry.

Background: Seasonal variation in fatality caused by stroke was examined using 15 years of data from a stroke registry of a Japanese population. Methods: Data were obtained from the Takashima Stroke Registry, which covers approximately 55,000 residents in central Japan. There were 1,650 registered cases of first-ever stroke between 1988 and 2002. 7- and 28-day fatality rates and 95% confidence intervals were calculated for winter, spring, summer and autumn. After adjusting for gender, age at onset and risk factors, the hazard ratios for fatal strokes in winter, spring and autumn were calculated, with summer serving as the reference. Results: For cerebral infarction, the highest 7- and 28-day fatality rates occurred during spring and winter, where they were more than double the rate during summer. The severest strokes were also more likely to occur during winter and spring. A high spring and winter hazard ratio for 28-day mortality was present in both lacunar and nonlacunar subtypes, in both genders and in subjects <65 and ≥65 years of age. No apparent seasonal pattern was observed for cerebral hemorrhage or subarachnoid hemorrhage. The spring and winter excess fatality persisted even after adjusting for age, gender and risk factors. Conclusion: Patients who suffer an ischemic stroke during winter or spring have a poorer prognosis. Further investigation is needed to determine the factors that explain this excess risk.

Case Fatality of Stroke and Day of the Week: Is the Weekend Effect an Artifact?

Background and Purpose: For stroke admissions, the ‘weekend effect’ has been associated with higher stroke fatality. However, it is unclear if stroke case fatality shows this pattern if the onset day is taken into account. Day of the week variation in stroke case fatality was examined using 16-year stroke registration data. Design and Methods: Data were obtained from Takashima Stroke Registry in central Japan. There were 1,578 registered first-ever cerebral infarction and cerebral hemorrhage stroke cases during 1988–2003. We divided the days into 2 groups: ‘weekend’ and ‘weekdays’. The 7-day and 28-day case fatality rates and 95% confidence intervals (95% CI) were calculated by gender, age and stroke subtype. Results: For all strokes, the 7-day case fatality rate based on the hospital admission day was 9.5% (95% CI: 6.8–13.1) for weekend admissions and 7.3% (95% CI: 6.0–8.9) for weekday admissions. However, case fatality rates based on the onset day were 7.2% (95% CI: 5.1–10.0) for weekend onset and 8.0% (95% CI: 6.6–9.8) for weekday onset. The 28-day case fatality rate for the weekend admission group was 14.7% (95% CI: 11.3–18.8) and for the weekday admission group it was 10.1% (95% CI: 8.5–11.9). In contrast, the 28-day case fatality rate for the weekend onset group was 11.3% (95% CI: 8.6–14.7) and for the weekday onset group it was 11.0% (95% CI: 9.3–13.0). This phenomenon was observed mainly for cerebral infarction and to some extent for cerebral hemorrhage. Conclusion: Stroke fatality rates based on the day of admission were higher during the weekend than weekdays, although the difference did not reach statistical significance. However, this trend disappeared when the fatality rate was based on the day of onset.