Age differences in the experience of pain in humans and animals

The studies in this dissertation asses age differences in the experience of pain in humans and animals and the appropriateness of pain assessment tools across the adult life-span. Chapter I reviews age differences in experimental, acute and chronic pain in humans. Chapter 2 reviews age differences in the outcome of psychological treatments for chronic pain. It is concluded do there are age differences in each type of pain and that the elderly appear to benefit from psychological treatments as much as younger groups. Several experiments were conducted to examine the concepts that the elderly believe that pain is an inevitable part of aging and are not distressed by it, and that they experience less interim pain than younger patients. However, Chapter 3 presents two studies which find no age differences in pain beliefs. Furthermore, the studies described in Chapters 4 and 5 suggest that there may be age differences in the perceived qualities of chronic pain, measured with the short and full form of the McGill Pain Questionnaire (MPQ), but no age differences in pain intensity measured with single-item scales The data from Chapters 3, 4 and 5 suggest that the affective and cognitive components of chronic pain do not differ among age groups. Analysis of the psychometric properties of the pain measures suggests that verbal descriptor scales of pain intensity and both forms of the MPQ may be appropriate for use across the adult life-span. However, visual analog scales may not be appropriate for use with the elderly. To further elucidate the effects of aging on pain, Chapter 6 reviews age differences in nociceptive responsivity and pain behaviours in the rat. This review suggests that reflexive responses to nociceptive stimuli may not be age dependent although sensitivity on tests of more highly organized behaviours may decrease with age. Chapter 7 presents studies of age differences in the formalin test, a model of tonic pain, which suggest a curvilinear relationship between tonic pain sensitivity and age with peak responsivity at mid-life. A model to explain this pattern is developed in Chapter 6. Implications for pain assessment and treatment, possible mechanisms for the age differences reported, and directions for future research are discussed.