Anxiety and depression in an older research population and their impact on clinical outcomes in a randomised controlled trial

Introduction: Anxiety and depression are common in older people living in the community. The aim of the study was to investigate their impact on clinical outcomes during a randomised controlled trial investigating the cost benefits of influenza vaccination in fit and healthy, independent living 65-74 year olds. Subjects and methods: A total of 729 people were recruited. Participants completed the hospital anxiety and depression scale (HADS) and EuroQol EQ-5D quality of life questionnaire immediately before receiving vaccination and every two months for the next six months after this. Side effects three days after vaccination and Barthel score at baseline were also recorded. Results: At baseline the prevalence of "definite" anxiety in this sample (HADS score greater than or equal to 11) was 4% and 1.2% of individuals had definite depression (HADS score greater than or equal to 11). Individuals with anxiety or depression (HADS score greater than or equal to8) were more likely to complain of systemic side effects after vaccination and have a lower Barthel index score (p<0.001). Quality of life as measured by the EQ-5D visual analogue scale was reduced (p<0.001) of all time periods in those individuals with both anxiety and depression (HADS score greater than or equal to8 on both scales). Conclusion: Although the prevalence of anxiety and depression in this sample was low, people with anxiety or depression were more likely to suffer from perceived side effects after influenza vaccine and have a lower Barthel and EQ-5D visual analogue score. In future studies the effect of anxiety and depression on older participants should be remembered and care taken to ensure that they do not affect results more than the intervention under study.