Asynchronous discussions have been widely used in education to support learning. Exploring the reasons why threads in asynchronous discussion forums die may help us improve our understanding of asynchronous discussions and lead to a more effective learning process. This study explored why threads in asynchronous discussion forums shut down. Two analytical methods, namely, content analysis and statistical analysis, were employed. The discussion postings were coded into various behavior patterns based on the work of Lu et al. (Computers in Human Behavior 27:946-955, 2011). Differences of behavior patterns between long lifespan threads and short lifespan threads were investigated and reasons why some threads die quickly was explored. The shortest lifespan threads that died after one or two comments were statistically analyzed. The results showed that there was a significant difference in the disagreement with added justification between long lifespan threads and short lifespan threads. Explanation oriented questions, disagreement against justification, fact oriented questions, new claim, thumbs up and thanks, to some extent, were significantly different between long lifespan threads and short lifespan threads. Agreement played a large part in shortest lifespan threads. Based on the results and further content analysis, many educational implications have emerged for designing asynchronous discussion activities and asynchronous discussion rules. For example, it is necessary to continuously encourage learners to express fresh ideas; rewards can be a way of encouraging high quality replies; learners need to give the reason or explanation why they agree or disagree with others' postings; learners should be encouraged to ask more explanatory questions or factual questions; and off topic comments should not be forbidden.