We examined the association of social activity with cognitive decline in 1138 
persons without dementia at baseline with a mean age of 79.6 (SD = 7.5) who were 
followed for up to 12 years (mean = 5.2; SD = 2.8). Using mixed models adjusted 
for age, sex, education, race, social network size, depression, chronic 
conditions, disability, neuroticism, extraversion, cognitive activity, and 
physical activity, more social activity was associated with less cognitive 
decline during average follow-up of 5.2 years (SD = 2.7). A one point increase 
in social activity score (range = 1-4.2; mean = 2.6; SD = 0.6) was associated 
with a 47% decrease in the rate of decline in global cognitive function (p < 
.001). The rate of global cognitive decline was reduced by an average of 70% in 
persons who were frequently socially active (score = 3.33, 90th percentile) 
compared to persons who were infrequently socially active (score = 1.83, 10th 
percentile). This association was similar across five domains of cognitive 
function. Sensitivity analyses revealed that individuals with the lowest levels 
of cognition or with mild cognitive impairment at baseline did not drive this 
relationship. These results confirm that more socially active older adults 
experience less cognitive decline in old age.