Intra- and interindividual differences in the within-person coupling between daily pain and affect of older adults.

The bidirectional interplay between chronic pain and negative affect is well-established in patient samples. However, less is known about the day-to-day relationship between pain and affect of older adults without severe illnesses and to what extent this association differs within and between individuals. A total of 224 participants (M = 77.6, SD = 6.2) reported their daily experience of pain, impairment by their pain and affect during 21 consecutive days. Multilevel modeling results showed that on days with increased pain individuals also reported less positive affect and more negative affect. Time-lagged results indicated a temporal carry-over from yesterday's pain to today's negative affect but not to today's positive affect. Moreover, on days when individuals reported stronger impairment by their pain, they showed a stronger within-person coupling between daily pain and affect in contrast to days with a weaker experience of daily impairment. Yesterday's pain and today's negative affect were more strongly associated within individuals who reported higher levels of impairment. Interindividual differences in the within-person coupling between daily pain and affect were found with regard to general physical health conditions and general satisfaction with health. This study demonstrated the importance of focusing on within-person couplings between daily pain and affect beyond patient samples in order to better understand the maintenance of emotional stability despite daily hassles in older adults' everyday lives.