A computer implemented method for detecting occupant position change on a support surface having a head end test zone with at least one head end test bladder and a foot end test zone with at least one foot end test bladder , the method comprising: counting a quantity of head zone pressurization and depressurization cycles that have occurred during a time interval, each cycle having a head zone peak pressure and a head zone trough pressure; counting a quantity of foot zone pressurization and depressurization cycles that have occurred during the time interval, each cycle having a foot zone peak pressure and a foot zone trough pressure; setting a first flag if the quantity of head zone pressure change cycles exceeds a head zone cycle count threshold; setting a second flag if the quantity of pressure change cycles in the foot zone exceeds a foot zone cycle count threshold; determining the average of the head zone peak pressures and the average of the head zone trough pressures during the time interval and determining the difference between the averaged head zone peak and trough pressures; determining the average of the foot zone peak pressures and the average of the foot zone trough pressures during the time interval and determining the difference between the averaged foot zone peak and trough pressures; setting a third flag if the difference of the head zone averaged peak and trough pressures exceeds a head end pressure difference threshold; setting a fourth flag if the difference of the foot zone averaged peak and trough pressures exceeds a foot end pressure difference threshold; and if the first, second, third and fourth flags are all set, inferring that the occupant has migrated longitudinally along the bed . counting a quantity of head zone pressurization and depressurization cycles that have occurred during a time interval, each cycle having a head zone peak pressure and a head zone trough pressure; counting a quantity of foot zone pressurization and depressurization cycles that have occurred during the time interval, each cycle having a foot zone peak pressure and a foot zone trough pressure; setting a first flag if the quantity of head zone pressure change cycles exceeds a head zone cycle count threshold; setting a second flag if the quantity of pressure change cycles in the foot zone exceeds a foot zone cycle count threshold; determining the average of the head zone peak pressures and the average of the head zone trough pressures during the time interval and determining the difference between the averaged head zone peak and trough pressures; determining the average of the foot zone peak pressures and the average of the foot zone trough pressures during the time interval and determining the difference between the averaged foot zone peak and trough pressures; setting a third flag if the difference of the head zone averaged peak and trough pressures exceeds a head end pressure difference threshold; setting a fourth flag if the difference of the foot zone averaged peak and trough pressures exceeds a foot end pressure difference threshold; and if the first, second, third and fourth flags are all set, inferring that the occupant has migrated longitudinally along the bed . <EOS>