Chen Z, et al. - Researchers aimed at determining the associations of adiposity with incidence of stroke types and effect mediation by blood pressure in Chinese men and women. A strong positive association of adiposity with ischaemic stroke was noted. This association was noted to be due to the effect of adiposity on blood pressure. Leanness, either per se or through some other factor (or factors), might increase risk for intracerebral haemorrhage, offsetting the protective effects of lower blood pressure.

Methods

• Researchers enrolled 512,891 adults (aged 30–79 years) in the China Kadoorie Biobank from ten areas (five urban and five rural) during 2004–08.
• Documentation of 32,448 strokes (about 90% confirmed by neuroimaging) among 489,301 participants without previous cardiovascular disease was observed during a median 9 years (IQR 8–10) of follow-up.
• They produced adjusted hazard ratios (HRs) for ischaemic stroke (n=25,210) and intracerebral haemorrhage (n=5380) associated with adiposity using Cox regression analysis.

Results

• Researchers noted mean baseline body-mass index (BMI) of 23·6 kg/m² (SD 3·2); a BMI of less than 25 kg/m² was recorded for 331,723 (67·8%) participants.
• Each 5 kg/m² higher BMI was associated with 8·3 mm Hg (SE 0·04) higher systolic blood pressure throughout the range examined (mean 17·1 kg/m² [SD 0·9] to 31·7 kg/m²[2·0]),.
• Positive association of BMI with ischaemic stroke was noted, with an HR of 1·30 (95% CI 1·28–1·33 per 5 kg/m² higher BMI), this was generally consistent with that predicted by equivalent differences in systolic blood pressure (1·25 [1·24–1·26]).
• For intracerebral haemorrhage (1·11 [1·07–1·16] per 5 kg/m² higher BMI), the HR was less extreme, and was much weaker than that predicted by the corresponding difference in systolic blood pressure (1·48 [1·46–1·50]).
• Similar associations with stroke types were noted with other adiposity measures.
• They noted that after adjustment for usual systolic blood pressure, the positive associations with ischaemic stroke were attenuated (1·05 [1·03–1·07] per 5 kg/m² higher BMI); for intracerebral haemorrhage, they were reversed (0·73 [0·70–0·77]).
• High adiposity (BMI >23 kg/m²) was noted to be associated with 14·7% of total stroke (16·5% of ischaemic stroke and 6·7% of intracerebral haemorrhage).