Decreased bone density means a reduction in the mineral content of bones, making them less strong than before. It is an early sign of osteoporosis, a condition where bones become fragile and more prone to fractures. Elderly people, especially postmenopausal women, are more likely to develop osteoporosis. Additionally, people who lack exercise, have a diet low in calcium and vitamin D, smoke, drink excessively, or have a family history of osteoporosis are also at higher risk. Maintaining a healthy lifestyle and regular check-ups can help prevent osteoporosis.