Peak bone mineral density (BMD) is one of the most important factors influencing the development of osteoporosis. It was predicted that a 10% increase in peak BMD will delay the onset of osteoporosis by 13 years. However, changes in peak BMD over time are unknown. This study aimed to investigate secular trends in peak BMD among young adults in the United States. Based on the National Health and Nutrition Examination Survey from 1999–2018, 3,975 males aged 19–28 years and 2370 females aged 31–40 years were our target population for estimating peak lumbar spine BMD. BMD was measured by dual-energy X-ray absorptiometry. Generalized linear models adjusted for multiple covariates were used to examine the secular trends in peak BMD in males and females, respectively. Secular trends for peak lumbar spine BMD from 1999–2000 to 2017–2018 were not statistically significant in males or females (all P_linear and P_quadratic > 0.05). Similar results were observed in race/ethnicity subgroups (all P_linear and P_quadratic > 0.05). However, in stratified analyses by obesity category, peak lumbar spine BMD in obese males and females increased from 1999–2000 to 2009–2010 and then decreased until 2017–2018, while peak lumbar spine BMD in non-obese females decreased from 1999–2000 to 2005–2006 and then increased until 2017–2018 (all P_quadratic < 0.05). Peak lumbar spine BMD was greater in obese males and females than in non-obese males and females up to 2009–2010, but not from 2011–2012 onwards. Overall, there were no significant secular trends in peak lumbar spine BMD. However, secular trends differed between obese and non-obese groups.

峰值骨矿物质密度（BMD）是影响骨质疏松症发展的最重要因素之一。据预测，峰值BMD增加10%将使骨质疏松症的发病延迟13年。然而，峰值 BMD 随时间的变化尚不清楚。本研究旨在调查美国年轻人骨密度峰值的长期趋势。根据1999-2018年全国健康与营养调查，3975名19-28岁男性和2370名31-40岁女性是我们估算腰椎骨密度峰值的目标人群。 BMD通过双能X射线吸收法测量。使用针对多个协变量调整的广义线性模型分别检查男性和女性峰值 BMD 的长期趋势。从 1999-2000 年到 2017-2018 年，男性或女性腰椎 BMD 峰值的长期趋势没有统计学意义（所有P_线性和P_二次 > 0.05）。在种族/族裔亚组中观察到类似的结果（所有P_线性和P_二次 > 0.05）。然而，在按肥胖类别进行分层分析中，肥胖男性和女性的峰值腰椎BMD从1999-2000年到2009-2010年有所增加，然后下降到2017-2018年，而非肥胖女性的峰值腰椎BMD从1999-2000年下降到 2005-2006 年，然后增加到 2017-2018 年（所有P_二次 < 0.05）。截至 2009 年至 2010 年，肥胖男性和女性的腰椎 BMD 峰值高于非肥胖男性和女性，但从 2011 年至 2012 年之后则不再如此。总体而言，腰椎 BMD 峰值没有显着的长期趋势。然而，肥胖和非肥胖群体的长期趋势有所不同。