Problems with the measures of gastrointestinal and cardiovascular symptom frequency in The Standard Shiftwork Index

The measures of gastrointestinal and cardiovascular health in The Standard Shiftwork Index (SSI; Barton, Costa, Smith, Spelten, Totterdell, and Folkard, 1995) purport to measure the frequency of 19 related symptoms using a 4-point rating scale, with response categories expressed in terms of a relative frequency: 'almost never', 'quite seldom', 'quite often', and 'almost always'. The present pilot study examined the relationship between frequency ratings of 11 gastrointestinal and 8 cardiovascular symptoms made on the SSI 4-point scale, and ratings of the same symptoms made on an alternative 9-point rating scale, which had response categories that were expressed in terms of an absolute value of symptom frequency (e.g. 'once a week'). Results obtained from a sample of 56 non-shiftworkers showed that the correlations between the two response formats were not high for any of the 11 gastrointestinal or 8 cardiovascular symptoms. Three of the relationships were non-significant. In addition, substantial variability in the interpretation of the response categories was detected between symptom items pertaining to both the gastrointestinal and cardiovascular subscales. The implications of these findings are discussed in relation to the current system of scoring individual symptom items, and the current aims within shiftwork research.

Keywords:

• Shiftwork
• Symptom Frequency
• Health Status Indicators
• Gastrointestinal System
• Cardiovascular System