I do not deal with health matters, so I will not tell you how humidity affects people, but I can tell you a little about it from a completely different, maybe a bit unusual side. If you want to put an instrument at home - a piano or a piano, but not a digital one, but a real, acoustic one, then in order to ensure optimal conditions for this instrument, the relative humidity in the room in which it is standing should be within the range of 40 - 65%. Too low humidity (dry air) may lead to various damages to the instrument, deteriorate the precision of the mechanisms, and adversely affect its sound. Too high humidity can also cause problems with the operation of the mechanisms, and the locking of the keys. The dry-wet-dry humidity fluctuations are the worst. The more stable the humidity the better for a piano. In old houses, the air humidity is usually adequate. On the other hand, in new houses and apartments, especially those with underfloor heating or ventilation systems with air vents, it is usually too dry during the heating season. The wood the piano is made of dries up in winter, becomes moist in spring, and this is how it works. When the humidity fluctuations are large, e.g. 20% in winter and 80-90% when it rains in spring or autumn, then again 20% - there is a high probability that the soundboard may break, weaken the holding of the outfit or disrupt the mechanisms. To counteract this, place an air humidifier in the room with the instrument for the heating season so that the relative humidity is kept at a level not lower than 40%. This avoids damage to the equipment. Outside the heating season, the humidifier is put aside, because the humidity is usually at safe levels. Similarly to pianos, the wooden floor (gaps and cracks may appear in the parquet or boards) and wooden furniture (the boards may deform) also react to humidity fluctuations. And in terms of what humidity can be optimal for people - I would say the same as for a piano. So in the middle, about 50%, not too low, not too high.
I do not deal with health matters, so I will not tell you how humidity affects people, but I can tell you a little about it from a completely different, maybe a bit unusual side. If you want to put an instrument at home - a piano or a piano, but not a digital one, but a real, acoustic one, then in order to ensure optimal conditions for this instrument, the relative humidity in the room in which it is standing should be within the range of 40 - 65%. Too low humidity (dry air) may lead to various damages to the instrument, deteriorate the precision of the mechanisms, and adversely affect its sound. Too high humidity can also cause problems with the operation of the mechanisms, and the locking of the keys. The dry-wet-dry humidity fluctuations are the worst. The more stable the humidity the better for a piano. In old houses, the air humidity is usually adequate. On the other hand, in new houses and apartments, especially those with underfloor heating or ventilation systems with air vents, it is usually too dry during the heating season. The wood the piano is made of dries up in winter, becomes moist in spring, and this is how it works. When the humidity fluctuations are large, e.g. 20% in winter and 80-90% when it rains in spring or autumn, then again 20% - there is a high probability that the soundboard may break, weaken the holding of the outfit or disrupt the mechanisms. To counteract this, place an air humidifier in the room with the instrument for the heating season so that the relative humidity is kept at a level not lower than 40%. This avoids damage to the equipment. Outside the heating season, the humidifier is put aside, because the humidity is usually at safe levels. Similarly to pianos, the wooden floor (gaps and cracks may appear in the parquet or boards) and wooden furniture (the boards may deform) also react to humidity fluctuations. And in terms of what humidity can be optimal for people - I would say the same as for a piano. So in the middle, about 50%, not too low, not too high.