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Table 1 Key findings showing the characteristics of categorisation amongst the exposure variables in epidemiological studies

From: Assessing the reporting of categorised quantitative variables in observational epidemiological studies

Characteristics of categorisation

% of articles & CI regions

Prevalence of categorisation

61% (CI = 39%, 80%)

Decision informing categorisation

Hypothesis-driven categories

7% (CI = 0%, 34%)

Unknown (reasons not provided in the articles)

93% (CI = 66%, 100%)

Criteria used for categorisation

Established external criteria (e.g., WHO standards)

14% (CI = 2%, 43%)

Arbitrary grouping

29% (CI = 8%, 58%)

Equally spaced interval grouping

36% (CI = 13%, 65)

Quantile grouping

21% (CI = 5%, 51%)

Number of categories used amongst grouped exposures

2

7% (CI = 0%, 34%)

3

7% (CI = 0%, 34%)

4

29% (CI = 8%, 58%)

5

29% (CI = 8%, 58%)

6

14% (CI = 2%, 34%)

10

14% (CI = 2%, 34%)

Proportion of trend testing

57% (CI = 29%, 82%)