A validation analysis of the Work Productivity and Activity Impairment questionnaire (WPAI) for assessing lost productivity due to symptoms of gastroesophageal reflux disease (GERD) has previously been reported, based on results from a cross-sectional study of a Swedish working population (N=136) visiting a general practitioner due to GERD. The construct validity of the WPAI-GERD was found to be high, and patients with symptoms of GERD (heartburn) reported an average of 2.5 hours absence from work (AW), 23% reduced productivity while at work (PW) and 30% reduced productivity while doing regular daily activities (PA) during the week preceding the consultation. OBJECTIVES: To carry out a further validation analysis of the WPAI-GERD by investigating the relationship between the different productivity variables obtained (AW, PW, PA). METHODS: Pearson correlation coefficients (PCC) between each productivity variable were calculated based on results from the original study population (including 27 patients without heartburn symptoms). Correlations were also assessed for each category of symptom severity in patients with heartburn (mild, n=30; moderate, n=64; severe, n=15). RESULTS: The correlation between PW and PA was found to be high and statistically significant (PCC 0.82, p<0.0001). This finding was consistent in patients with either mild, moderate or severe heartburn. A positive relationship was also found between AW and PW (PCC 0.57, p<0.0001), as well as between AW and PA (PCC 0.52, p<0.0001). The PCC between AW and PW increased with heartburn severity (mild: -0.19, moderate: 0.48, severe: 0.78), since the proportion of patients reporting any absence from work increased with heartburn severity (mild: 7%, moderate: 28%, severe: 33%). Thus, results indicate that in patients with moderate or severe heartburn, absence from work is also associated with reduced productivity while at work. CONCLUSIONS: Results further support the construct validity of the WPAI-GERD.