The present study explored the relationship between the ankle-brachial index (ABI) (>.9) and all-cause or cardio-cerebrovascular mortality. Participant details were obtained from the National Health and Nutrition Examination Survey 1999-2004. The association between baseline ABI and the risk of mortality was evaluated by a priori defined quartile categories and on a continuous scale (per .1-unit change) with Cox regression models adjusted for demographic and traditional risk factors. A total of 7087 individuals (age: 59.6 ± 12.8 years) were included; 3612 (51.0%) were male. After an average follow-up of 12.2 years, 1926 deaths occurred. Kaplan-Meier analysis showed that the lowest ABI quartile (<1.06) was associated with the highest risk of all-cause, cardio-cerebrovascular and cancer mortality (all P < .001). However, after adjusting for potential confounders, ABI ranging between 1.06 and 1.12 was associated with the lowest risk of all-cause mortality (hazard ratio .88, 95% confidence interval .78-1.00, P < .05) compared with the reference group (<1.06). Besides, splines showed the relationship was nonlinear (P < .05) and the inflection point was 1.11. In conclusion, the level of ABI associated with the lowest risk of all-cause mortality was 1.11, under which a lower ABI was independently associated with an increased risk of all-cause mortality.
Keywords: all-cause mortality; ankle-brachial index; arterial calcification; cardio-cerebrovascular mortality; peripheral arterial disease.