Background:
To evaluate risk factors for intraparenchymal hemorrhage (IPH) by its subtypes may contribute to more effective prevention of IPH, but few prospective studies have characterized risk factors for specific subtypes of IPH.
Hypothesis:
We assessed the hypothesis that the associations between traditional risk factors such as blood pressures and risk of IPH vary by IPH subtype.
Methods:
A prospective study of Japanese subjects aged 40-69 years was undertaken using the data collected from 9,086 participants (3,560 men and 5,526 women) in cardiovascular risk surveys of three communities between 1985 and 1994. The incidence of IPH between 1985 and 2008 was ascertained by systematic surveillance. The location of hemorrhage was assigned based on admission CT scan or MRI by trained physicians. IPH selectively involving the thalamus, basal ganglia or brainstem was defined as deep IPH, while IPH isolated to the cortex was defined as lobar. The hazard ratios (HRs) of incidence of IPH and its subtypes (deep IPH and lobar or cerebellar IPH) and 95% confidence intervals (CI) relative to the baseline variables were calculated with adjustment for age and other potential confounding factors using the Cox proportional hazards model.
Results:
During an average follow up of 19.2-years, 139 incident IPHs (103 deep, 31 lobar or cerebellar, and 5 mixed or unclassified IPHs) occurred. Systolic blood pressure, major ST-T abnormality on electrocardiogram, and excess ethanol intake (≥46g/day) were associated with increased risk of deep IPH, while serum total cholesterol levels was inversely associated with incidence of lobar and cerebellar IPH, even after adjustment for potential confounding variables. Serum total cholesterol levels also tended to be inversely associated with incidence of deep IPH, although it did not reach statistically significance. The multivariate-adjusted HRs (95%CI) of deep IPH were 1.14 (1.05-1.23) for systolic blood pressure (10mmHg), 2.09 (1.19- 3.66) for major ST-T abnormality, and 1.86 (1.02- 3.38) for excess ethanol intake. The adjusted HR (95%CI) of lobar and cerebellar IPH was 0.22 (0.07- 0.76) for the participants with higher total cholesterol levels (≥220 mg/dL), compared with those with lower total cholesterol levels (<160mg/dL). There were no associations of diabetes mellitus and smoking with both deep and lobar/cerebellar IPH.
Conclusions:
Impact of risk factors on incidence of IPH varied according to its subtype.
Bivariate variance-component analysis, with application to systolic blood pressure and total cholesterol levels in the Framingham Heart Study