A sudden decrease in height might be due to osteoporosis. Osteoporosis is a condition where bones become weak and are more likely to fracture, commonly seen in older adults. As bone density decreases, the vertebrae can compress or collapse, leading to a reduction in height. Besides height loss, osteoporosis may also cause back pain and fractures. If you notice a decrease in your height, especially with pain, it is advisable to visit a doctor. Osteoporosis can be managed through diet, exercise, and medication.