## Standardised ratio of multiple to underlying

The ‘standardised ratio of multiple to underlying’ (SRMU) describes the extent to which a cause is involved in the death (multiple cause) compared to its involvement only as the underlying cause (Désesquelles et al. 2010). It shows the extent to which people die due to a cause compared with dying with the cause.

The SRMU is calculated for a specific cause. It is a rate ratio; specifically the ratio of the age-standardised mortality rate based on the multiple cause involvement to the age-standardised mortality rate based on the underlying cause. The SRMU is calculated as follows:

where:

• ASRM is the age-standardised rate based on the multiple cause
• ASRU is the age-standardised rate based on the underlying cause.
• A guide to the interpretation of the SRMU is shown in the table below.

#### Table: Interpretation of the standardised ratio of multiple to underlying

Underlying cause rate
(ASRU)

Multiple cause rate
(ASRM)

SRMU
(ASRM/ASRU)

Interpretation

150 deaths per 100,000

150 deaths per 100,000

1.0

Most likely to die from, than with, the cause
(Cause is always the underlying cause)

150 deaths per 100,000

225 deaths per 100,000

1.5

More likely to die from, than with, the cause

150 deaths per 100,000

300 deaths per 100,000

2.0

Equally likely to die from or with the cause

150 deaths per 100,000

780 deaths per 100,000

5.2

More likely to die with, than from, the cause

0 deaths per 100,000

150 deaths per 100,000

. .

Most likely to die with, than from, the cause
(Cause is never the underlying cause)

.. not applicable