A large number of factors in the aging process contribute to the elderly's susceptibility to physical ill-health. The defence systems against disease decline by 20% of their peak. Between the ages of 30 to 70 the average person loses 30 to 40% of the body's mass. The heart's pumping efficiency drops 30% in the same period. By 40 years of age men and women begin to lose bone because of a decreased ability to absorb calcium.