How do I choose an effect measure from the raw outcome type in a winter-health review?

Classify each outcome as binary, continuous, or time-to-event, then pair it with a compatible effect measure and record the measure, its scale, and the raw data format in a decision table your analysis plan can cite. Cochrane Handbook Chapter 10 covers effect measures alongside fixed and random effects, heterogeneity, missing data, and forest plots, so the classification step belongs at the start of planning the meta-analysis.

Decision sequence

1. Label the outcome type from the raw data you will extract. Binary outcomes count participants in each group by event status; continuous outcomes report a mean and a measure of spread per group; time-to-event outcomes report the time until the event plus censoring information. Expected result: every outcome in the review carries one label.
2. Match the label to a compatible effect measure. Binary data support ratio measures such as risk ratios or odds ratios and difference measures such as risk differences; continuous data support mean differences when studies share a scale and standardized mean differences when they use different scales; time-to-event data support hazard ratios. Expected result: one candidate measure per outcome.
3. Check that the raw data format supports the chosen measure. Confirm the extracted fields match what the measure needs, such as event counts and group totals for binary measures or group means, standard deviations, and sample sizes for continuous measures. Expected result: a gap list of fields still to extract or request.
4. Record the decision in a table with columns for outcome, outcome type, chosen measure, scale, and raw data format. Expected result: a citable record that the analysis plan and any later sensitivity analysis can reference.
5. Revisit the table when a study reports an outcome in an incompatible format, and note the conversion or exclusion decision in the same row. Expected result: a traceable record of every deviation from the original plan.

Chapter 15 of the Cochrane Handbook addresses interpretation of confidence intervals, absolute and relative effects, and applicability, which helps when you explain in the review why a given measure was chosen for a given outcome.