{"doi":"10.1093/jnci/djab009","title":"Timing of Aspirin Use in Colorectal Cancer Chemoprevention: A Prospective Cohort Study","abstract":"BACKGROUND: Prior epidemiological and intervention studies have not been able to separate independent effects of dose, timing, and duration of aspirin use in colorectal cancer (CRC) chemoprevention. We examined aspirin-based CRC chemoprevention according to timing in the Nurses' Health Study and Health Professionals Follow-Up Study. METHODS: The exposures include cumulative average dose and total duration of aspirin use in more than 10 years before follow-up started (remote period) and in the immediate 10 years before follow-up started (recent period). Cox models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for exposures and CRC risk. RESULTS: Aspirin use of longer than 10 years before follow-up started (HR = 0.88, 95% CI = 0.83 to 0.94) per 5-year increment and the immediate 10 years before follow-up started (HR = 0.90, 95% CI = 0.84 to 0.96) were similarly important in CRC chemoprevention, though a 5-year lag was required for a clear benefit in the recent period. In the remote period, the association was not dose dependent; compared with less than 0.5 standard-dose (325 mg) tablets per week; hazard ratios were 0.78 (95% CI = 0.63 to 0.98), 0.81 (95% CI = 0.72 to 0.91), and 0.74 (95% CI = 0.64 to 0.86) for doses of 0.5 to less than 1.5, 1.5 to less than 5, and 5 and more tablets per week, respectively. However, there was dose dependency in the recent period (with respective HR = 0.91, 95% CI = 0.79 to 1.06; HR = 0.87, 95% CI = 0.77 to 0.98; and HR = 0.76, 95% CI = 0.64 to 0.91). CONCLUSIONS: A suggestive benefit necessitates at least 6-10 years and most clearly after approximately 10 years since initiation of aspirin. Remote use and use within the previous 10 years both contribute independently to decrease risk, though a lower dose may be required for a benefit with longer term use.","journal":"JNCI Journal of the National Cancer Institute","year":2021,"id":167128,"datarank":0.5244761342199721,"base_score":3.4965075614664802,"endowment":3.4965075614664802,"self_citation_contribution":0.5244761342199721,"citation_network_contribution":0.0,"self_endowment_contribution":0.5244761342199721,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":32,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.8129,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":41038,"name":"Andrew T. Chan","orcid":"0000-0001-7284-6767","position":1,"is_corresponding":false},{"id":6441,"name":"Jeffrey A. Meyerhardt","orcid":"0000-0002-1120-0898","position":2,"is_corresponding":false},{"id":86230,"name":"Edward L. Giovannucci","orcid":"0000-0002-6123-0219","position":3,"is_corresponding":false},{"id":382879,"name":"Yin Zhang","orcid":"0000-0001-6367-6583","position":0,"is_corresponding":true}],"reference_count":63,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-18T23:45:54.042727Z","pmid":"33528007","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}