The impact of risk factor trends on intracerebral hemorrhage incidence over the last two decades-The Tromsø Study

Background: Studies on the relationship between temporal trends in risk factors and incidence rates of intracerebral hemorrhage are scarce.

Aims: To analyze temporal trends in risk factors and incidence rates of intracerebral hemorrhage using individual data from a population-based study.

Methods: We included 28,167 participants of the Tromsø Study enrolled between 1994 and 2008. First-ever intracerebral hemorrhages were registered through 31 December 2013. Hazard ratios (HRs) for intracerebral hemorrhage were analyzed by Cox proportional hazards models, risk factor levels over time by generalized estimating equations, and incidence rate ratios (IRR) by Poisson regression.

Results: We registered 219 intracerebral hemorrhages. Age, male sex, systolic blood pressure (BP), diastolic BP, and hypertension were associated with intracerebral hemorrhage. Hypertension was more strongly associated with non-lobar intracerebral hemorrhage (HR 5.08, 95% CI 2.86-9.01) than lobar intracerebral hemorrhage (HR 1.91, 95% CI 1.12-3.25). In women, incidence decreased significantly (IRR 0.46, 95% CI 0.23-0.90), driven by a decrease in non-lobar intracerebral hemorrhage. Incidence rates in men remained stable (IRR 1.27, 95% CI 0.69-2.31). BP levels were lower and decreased more steeply in women than in men. The majority with hypertension were untreated, and a high proportion of those treated did not reach treatment goals.

Conclusions: We observed a significant decrease in intracerebral hemorrhage incidence in women, but not in men. A steeper BP decrease in women may have contributed to the diverging trends. The high proportion of untreated and sub-optimally treated hypertension calls for improved strategies for prevention of intracerebral hemorrhage.