Alzheimer's disease (AD) and osteoporosis are common chronic degenerative disorders which are strongly associated with advanced age. Some studies suggest that low bone mineral density (BMD) is related to the increased risk of AD. We conducted a 5-year prospective study to exam the association between BMD and the risk of AD in a cohort of Chinese elderly people. Of 3263 community residents aged 65 years and over, 2019 were enrolled into the study and followed up annually for 5 years. At baseline demographic data, smoking and drinking status, medical history, cognitive status, and blood samples were collected. BMD was measured by dual energy X-ray absorptiometry (DEXA) scanning at baseline and during follow-up. Cox proportional hazards analysis was used to evaluate the association with BMD and incidence of AD. Over the follow-up of 5 years, AD developed in 132 subjects. Baseline BMD, bone loss rate, current smoking, and daily drinking were associated with increased risk of AD, while higher baseline plasma leptin level was associated with decreased risk of AD, in both women and men. Low BMD and increased loss rate of BMD were associated with higher risk of AD. Cigarette smoking, alcohol drinking, and lower leptin level are risk factors for AD. Uncovering the relation linking osteoporosis and AD is important for understanding the pathogenesis and developing therapeutic strategies for these two common disorders afflicting elderly people.