Validity of a measure of the frequency of headaches with overt neck involvement, and reliability of measurement of cervical spine anthropometric and muscle performance factors

Objective: To test the validity of a questionnaire to measure frequency of headaches related to the neck. A secondary goal was to test the reliability of field measurement of associated cervical spine anthropometric and muscl e performance factors. Design: Intermethod and test-retest comparisons. Setting: Two municipalities in a rural area of Tasmania, Australia. Participants: One hundred subjects were selected as a representative sample of never-injured adults from a comprehensive listing of the source populat ion, and 93 participated. Main Outcome Measures: Subjects distinguished headaches matching three crit eria for overt neck involvement, reported past-month frequency by questionn aire, and recorded in a diary occurrences during the next month. Measuremen ts of height, weight, neck column length and circumference, lateral flexion and extension range of movement, cervical short flexor muscle endurance, a nd cervical long flexor and extensor strength were taken at the start and e nd of the month. Results: Headache frequency was associated with neck stiffness and neck ach e. There was moderate agreement (weighted K = .66) between questionnaire an d diary, but better agreement (K = .72) for subjects who maintained their u sual patterns of recreational sport. For this group, the correlation with " true" frequency was r(u) = .87. The anthropometric and muscle performance f actors were reliably measured (intraclass correlations .96 to 1.00, kappa . 78 to .86) despite minor improve ment in muscle performance on retest. Conclusions: The questionnaire measure has construct validity. Neck-related headaches are a temporally stable presentation in never-injured subjects w ho maintain customary sporting activity. Measurement error was consequentia l, but less so for this group than for the study subjects generally. The an thropometric and muscle performance measurements were reliable, but slight improvements on retest suggest the need for multiple measurements.