Faculty of Medicine


Recent Submissions

  • Rautalin, Ilari (Helsingin yliopisto, 2021)
    Aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening stroke type that kills around 40% of patients within the first months following the event. Due to the relatively low incidence (~8 per 100 000), high sudden-death rate (~25% of patients) and complex origin (combination of genetic and environmental risk factors), investigating aSAH risk factors is extremely challenging. By exploiting several unique cohort studies from Finland and Norway, this thesis aimed to clarify the role of lifestyle-related risk factors on aSAH and its mortality. First, we investigated the relationships between aSAH risk and physical activity on 65 521 Finnish participants by utilizing a large, prospective, longitudinal and population-based cohort study called the National FINRISK study. Second, we pooled the data of the FINRISK cohort with two similar prospective population-based cohorts from Norway, namely the HUNT and Tromsø studies, and used the data of 211 949 adult individuals to investigate the relationship between aSAH risk and obesity. Third, we conducted a systematic review to evaluate the quality of previous literature concerning the obesity paradox (previously reported theory suggesting that obesity may protect critically ill patients from mortality) in aSAH patients. Lastly, in order to evaluate whether smoking contributes to familial manifestation of aSAH, we utilized an older Finnish Twin Cohort including comprehensive data of 16 282 same-sex twin pairs. We found that physical activity during leisure time and commuting was associated with a decreased aSAH risk in both men and women. In addition, these activities diminished the adverse effects of hypertension and smoking. In terms of obesity, we found that the previously reported protective effect of obesity on aSAH risk may be explained by the distorting effects of smoking and hypertension on this association. Therefore, the independent role of obesity on aSAH risk seems to be modest. According to our systematic review, the evidence behind the obesity paradox on aSAH is very limited and no definite conclusions can be drawn based on the previous literature. Finally, for the first time, we found that smoking was strongly associated with the risk of fatal aSAH within twin pairs, indicating that smoking has a causal – rather than simply associative – effect on aSAH. Based on the comprehensive literature search and several large, long-term and high-quality cohort studies, this thesis clarifies the role of several lifestyle-related factors – particularly physical inactivity, obesity and smoking – on aSAH risk and its mortality. By means of our findings, the incidence, mortality and overall burden of aSAH can likely be decreased in the future.