Doctors Say It Was Probably The Cold Medicine
A piece on MedPage Today by Jeffrey Sonnenfeld, DBA, MBA, and Harlan Krumholz, MD, SM entitled, "Did Cold Medications Affect Biden's Debate Performance?" seems to answer the questions:
In response to a question about abortion, Biden hesitatingly offered jumbled canned lines about immigration while staring dazed, mouth agape during breaks. This is not the president we have seen in the last 3 years or even the last few weeks.
As time passed, the fog lifted. He improved throughout the debate and later in the evening, engaging with people far into the night. The next day, he delivered a fiery speech in North Carolina without missing a beat. The short half-life of many of these drugs could explain Biden's resilient post-debate appearances.
Biden's symptoms appeared consistent with someone suffering from temporary drug-induced cognitive impairment. We now know he had a bad cold during the debate. Most people believe common over-the-counter cold medications such as DayQuil, Tylenol, or Advil to be harmless. While generally well tolerated, these medications have well-documented side effects and can cause reduced alertness, diminished attention, poor memory, and reduced reaction time, especially in older individuals. These impairments are transitory but can appear consequential and alarming. Every experienced clinician has seen this effect thousands of times. If anti-cold medications were combined with other drugs, the risks could increase even more.