Footnotes

• X @danlarach, @drchadb

• Contributors DBL designed data collection tools, monitored data collection for the whole trial, wrote the statistical analysis plan, cleaned and analyzed the data, and drafted and revised the paper. He is guarantor. KL cleaned and analyzed the data and drafted and revised the paper. TDB designed data collection tools, monitored data collection for the whole trial, and drafted and revised the paper. GM designed data collection tools, monitored data collection for the whole trial, and drafted and revised the paper. DAE designed data collection tools and drafted and revised the paper. BF wrote the statistical analysis plan, cleaned and analyzed the data, and drafted and revised the paper. SO designed data collection tools and drafted and revised the paper. CMB designed data collection tools and drafted and revised the paper. SB designed data collection tools, wrote the statistical analysis plan, cleaned and analyzed the data, and drafted and revised the paper.

• Funding The authors report funding for this manuscript from the USC Roybal Center for Behavioral Interventions in Aging (Los Angeles, CA), the National Institute on Aging (Bethesda, MD; P30AG024968 and R01AG085287), the National Institute of General Medical Sciences (Bethesda, MD; T32GM108554), the National Institute on Drug Abuse (Rockville, MD; K23DA057387 and R01DA050334) and the National Center for Advancing Translational Sciences (Bethesda, MD; UL1TR000445).

• Competing interests CMB is a consultant for Merck Pharmaceuticals (Rahway, NJ) and Vertex Pharmaceutical (Boston, MA) and provides expert medical testimony. He was previously a consultant for Heron Therapeutics (San Diego, CA). SB is a consultant for AKIGAI (Kristiansand, Norway) and provides expert medical testimony. These activities are unrelated to the content of this manuscript.

• Provenance and peer review Not commissioned; externally peer-reviewed.

• Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.