A composition comprises a) at least one ethylene-based copolymer comprising units derived from ethylene and from greater than 0 wt% to less than or equal to 3.5 wt%, based on the total weight of the ethylene-based copolymer, of units derived from at least one polar comonomer; b) at least one antioxidant; c) an organic peroxide; d) optionally, at least one co-agent; and e) optionally, at least onewater tree retardant or electrical tree retardant. The composition comprises from 0 wt% to less than 1 wt%, based on the total weight of the composition, of olefin-based polymers other than the ethylene-based copolymer. The composition has a dissipation factor of from 0% to less than or equal to 0.1% at a temperature of 120 DEG C and an electrical stress of 6 kV/mm. The composition is suitable foruse as an insulation layer in cables.