Why hypertension is not the first leading cause of death? - The problems related to the selection rules for underlying cause of death

Cause-of-death statistics are the most highly used reference in public health planning and evaluation. To understand why hypertension, a highly prevalent disease in Taiwan, is not the leading cause of death, this article first introduces the concept of underlying cause-of-death (UCOD), and the selection rules that guide the tabulation of cause-of-death statistics. The linkage rule of the selection rules is the main reason that hypertension would not be selected as the UCOD. According to this rule, when a death certificate lists hypertension with mention of ischemic heart disease, cerebrovascular disease, and nephritic syndrome, hypertension would not be selected as the UCOD. This article also reviews previous studies on the reliability and validity of UCOD coding processes. Reasons explaining the variation in UCOD coding among different countries include 1) differences in the procedure of collecting cause-of-death information (e.g., certifier requirements, format of cause-of-death diagnosis, percentage of deaths in hospitals, autopsy rates, criteria of query); 2) differences in customs of diagnosing cause of death; 3) differences in interpretation of disease causal relationships; and 4) vague and paradox of selection rules. Two solutions to the abovementioned problems are tabulation of multiple causes of death, and automation of UCOD selection.