An audit of the association between the use of antipsychotic medication and bone density measurement in female patients within a special (high security) hospital

There is considerable variation among the antipsychotic drugs in terms of their capacity to increase serum prolactin, but the clinical relevance of this to osteoporosis is unclear. This paper describes an audit of bone density measurement in a long-term psychiatric population specifically conducted to examine any association between prolactin level and use of antipsychotic medication. A sample of 31 female patients from one high security hospital underwent dual energy X-ray absorptiometry of their wrist bones. Information relating to risk factors for osteoporosis was collected by questionnaire from the patients, and the pharmacy department provided details of current medications. A logistic regression was carried out on the dependent variable of osteoporosis (i. e., osteopenia/osteoporosis and normal) as determined from the distal T score of the bone density measurement, with age at interview, smoking, length of time on antipsychotic medication, serum prolactin measurement, whether or not the patient was taking thyroxine, and body mass index all entered as independent variables. The only variable found to have a significant independent effect on osteopenia/osteoporosis was body mass index: the higher the body mass index, the higher the distal T score. This suggests that weight, rather than antipsychotic medication use, appears to influence bone density more than prolactin level, with obesity seemingly having a protective role.