As we age, the body starts also to deteriorate. When you reach the age 50, stiffness and pain can be felt.  You will notice a decline in your vision, muscle strength, and the rest of your body functions.  Of course not all experience the early onset of weakening.  Your activity, environment, food, and your lifestyle in the past will have the effect as you grow older.  Experts say moderate regular exercise and right food intake will protect your heart and yourself from age related diseases.  There are many ways and guides today to boost your immunity and become healthy.  But it is better to have a regular visit to the doctor and undergo ultra sound, urine and blood test, or executive check-up to be able to monitor the signs of a disease.  This may not be possible for everybody for financial reasons.  Find ways to make yourself healthy thru reading.  There are good references that you can find in the internet for staying healthy.