To drink or not to drink: How are alcohol, caffeine and past smoking related to bone mineral density in elderly women?

Objectives: To determine relationship between alcohol, caffeine, past smoking and bone mineral density of different skeletal sites in elderly women, accounting for other biological and life-style variables. Methods/Design: A cross-sectional study in 136 Caucasian women, mean +/- SD age 68.6 +/- 7.1 years, all healthy and free of medications affecting bones, including estrogen. Bone mineral density (BMD) of multiple skeletal regions and body composition were measured by dual X-ray absorptiometry. Serum vitamin D (25-OHD) and parathyroid hormone (PTH) were analyzed and used as confounders. Calcium (Ca) intake was assessed by food frequency questionnaire. Alcohol and caffeine consumption was assessed by questionnaires determining frequency, amount and source of each. There were no current smokers, but the history of smoking was recorded, including number of years and packages smoked/day. Past physical activity was assessed by Allied Dunbar National Fitness Survey and used as confounder. Statistical significance was considered at p less than or equal to 0.05. Results: In the correlational analysis, alcohol was positively associated with spine BMD (r = 0.197, p = 0.02), 25-OHD and negatively with PTH. Smoking was negatively related to Ca intake, 25(OH)D and number of reproductive years. In subgroup (stratified by Ca intake) and multiple regression analyses, alcohol (average similar to0.5-1 drinks/day or similar to8 g alcohol/day) was favorably associated with BMD of spine and total body. Caffeine (average similar to2.5 6-fl oz cups/day or 200-300 mg caffeine/day) had negative association with most of the skeletal sites, which was attenuated with higher Ca intake (greater than or equal tomedian, 750 mg/day). The past smokers who smoked on average 24 years of similar to1 pack cigarettes/day had lower BMD in total body, spine and femur than never-smokers when evaluated in subgroup analyses, and the association was attenuated in participants with greater than or equal tomedian Ca intake. There was no significant association between past smoking and BMD of any skeletal site in multiple regression analyses. Conclusion: The results support the notion that consumption of small/moderate amount of alcohol is positively, while caffeine and past smoking are negatively associated with most of the skeletal sites, which might be attenuated with Ca intake above 750 mg/day.