Based on the study entitled Effects of Altitude, Shade, Yield and Fertilization on Coffee Quality (Coffea arabica L. var. Caturra) produced in Agroforestry
Systems of the Northern Central Zones of Nicaragua the summary describes following on the altitude subject:
...
Altitude had the strongest influence on coffee physical
characteristics, biochemical composition and organoleptic quality.
Shade influenced significantly the physical characteristics and
biochemical composition of coffee beans; nonetheless, the organoleptic
quality was significantly enhanced by shade only in the altitudinal
range of 950-1255 m. Fertilization and yield influenced positively
physical characteristics of the coffee beans as well as their
biochemical composition. The organoleptic quality was influenced by
fertilization, but not by yield. Biochemical compounds showed strong
relationships with organoleptic characteristics.