Why does vital capacity decreases with aging?

aging in the process decreases metabolism which in effect reduced the quality of body functions  as we get older

Vital Sign Capacity with age due to anatomical, physiological  and immunological changes that weaken the respiratory system over time. with age due to physiological, anatomical and immunological changes that weaken the respiratory system over time.

It is due to physiological, anatomical and immunological changes that weaken the respiratory system over time.

forinsstance, there is change in  temprerature regulation due to loss of subcutaneous fat,and reduced ability to sweat. also blood pressure changes due to loss or less elestic in blood vessels which leads to increase blood pressure.