Smoking and intervertebral disc degeneration.

Cigarette smokers have an increased risk of low back pain which may be caused by disc degeneration and spinal instability, for example. Ischemia, apoptosis, faulty synthesis of disc macromolecules, and an imbalance between disc matrix proteinases and their inhibitors may be involved in the pathogenesis of disc degeneration. Along with degeneration, the primary avascular disc turns vascular. There is some evidence that disc degeneration of cigarette smokers is of more severe degree than that of non-smokers.Cigarette-smoking increases serum proteolytic activity by releasing proteolytic enzymes from neutrophils in alveolar capillaries, and by inhibiting the activity of alpha-1-antiprotease, the most potent protease inhibitor. We hypothesize that the high serum proteolytic activity of cigarette-smokers gets access to a previously degenerated neovascularized disc and speeds up the degerative process. The increased proteolytic activity may also weaken the spinal ligaments resulting in spinal instability. These processes may explain the increased risk of low back pain of cigarette smokers.

Diurnal blood pressure variations and onset of subarachnoid haemorrhage: a population-based study.

OBJECTIVES: To analyse the association between time of onset of subarachnoid haemorrhage and diurnal blood pressure variations of ambulant normo- and hypertensive subjects. DESIGN: Retrospective, population-based study. SETTING: The population (246,000) of the Health Care District of Central Finland. PATIENTS: During 1980-1987 a total of 332 subjects in the study population had their first subarachnoid haemorrhage. The hour of onset could be obtained for 287 patients, and these form the basis of the present study. RESULTS: The onset of subarachnoid haemorrhage occurred significantly more often during the waking hours than during the night. The correlation between the hourly numbers of patients suffering a haemorrhage and the corresponding mean systolic and diastolic blood pressure values of ambulant normo- and hypertensive subjects was highly significant (r = 0.88, P < 0.001). The results were similar when the 224 patients with proved aneurysmal bleed were analysed separately (r = 0.79-0.85, P < 0.001). CONCLUSIONS: The diurnal blood pressure variations of ambulant normo- and hypertensive subjects, especially the transient blood pressure peaks reaching much higher levels of pressure during the waking hours than during the night, may be crucial in determining the time of rupture of a critically weakened aneurysm wall.