Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
JAMA Netw Open. 2024 May 1;7(5):e2412854. doi: 10.1001/jamanetworkopen.2024.12854.
Early menarche is associated with adverse health outcomes. Trends toward earlier menarche have been observed in the US, but data remain limited on differences by sociodemographic factors and body mass index (BMI). Time from menarche to cycle regularity is another understudied early-life characteristic with health implications.
To evaluate the temporal trends and disparities in menarche and time to regularity and explore early-life BMI as a mediator.
DESIGN, SETTING, AND PARTICIPANTS: This ongoing cohort study enrolled participants from an ongoing mobile application-based US cohort from November 14, 2019, to March 20, 2023.
Birth year (categorized as 1950-1969, 1970-1979, 1980-1989, 1990-1999, and 2000-2005).
Main outcomes were age at menarche and time to regularity, which were self-recalled at enrollment. In addition, early (aged <11 years), very early (aged <9 years), and late (aged ≥16 years) age at menarche was assessed.
Among the 71 341 female individuals who were analyzed (mean [SD] age at menarche, 12.2 [1.6] years; 2228 [3.1%] Asian, 3665 [5.1%] non-Hispanic Black, 4918 [6.9%] Hispanic, 49 518 [69.4%] non-Hispanic White, and 8461 [11.9%] other or multiple races or ethnicities), 5223 were born in 1950 to 1969, 12 226 in 1970 to 1979, 22 086 in 1980 to 1989, 23 894 in 1990 to 1999, and 7912 in 2000 to 2005. The mean (SD) age at menarche decreased from 12.5 (1.6) years in 1950 to 1969 to 11.9 (1.5) years in 2000 to 2005. The number of individuals experiencing early menarche increased from 449 (8.6%) to 1223 (15.5%), the number of individuals experiencing very early menarche increased from 31 (0.6%) to 110 (1.4%), and the number of individuals experiencing late menarche decreased from 286 (5.5%) to 137 (1.7%). For 61 932 participants with reported time to regularity, the number reaching regularity within 2 years decreased from 3463 (76.3%) to 4075 (56.0%), and the number not yet in regular cycles increased from 153 (3.4%) to 1375 (18.9%). The magnitude of the trend toward earlier menarche was greater among participants who self-identified as Asian, non-Hispanic Black, or other or multiple races (vs non-Hispanic White) (P = .003 for interaction) and among participants self-rated with low (vs high) socioeconomic status (P < .001 for interaction). Within a subset of 9865 participants with data on BMI at menarche, exploratory mediation analysis estimated that 46% (95% CI, 35%-61%) of the temporal trend in age at menarche was explained by BMI.
In this cohort study of 71 341 individuals in the US, as birth year increased, mean age at menarche decreased and time to regularity increased. The trends were stronger among racial and ethnic minority groups and individuals of low self-rated socioeconomic status. These trends may contribute to the increase in adverse health outcomes and disparities in the US.
初潮提前与不良健康结果有关。美国已经观察到初潮提前的趋势，但关于社会人口因素和体重指数 (BMI) 差异的数据仍然有限。从初潮到周期规律的时间是另一个研究较少的与健康相关的生命早期特征。
评估初潮和规律时间的时间趋势和差异，并探讨早期 BMI 作为中介的作用。
设计、地点和参与者：本正在进行的队列研究纳入了 2019 年 11 月 14 日至 2023 年 3 月 20 日期间来自一个基于移动应用的美国队列研究的参与者。
出生年份（分为 1950-1969 年、1970-1979 年、1980-1989 年、1990-1999 年和 2000-2005 年）。
主要结局是初潮年龄和规律时间，这是在入组时自我回忆的。此外，还评估了初潮（年龄<11 岁）、极早潮（年龄<9 岁）和晚潮（年龄≥16 岁）。
在分析的 71341 名女性个体中（初潮年龄的平均[SD]为 12.2[1.6]岁；2228 名[3.1%]为亚裔、3665 名[5.1%]为非西班牙裔黑人、4918 名[6.9%]为西班牙裔、49518 名[69.4%]为非西班牙裔白人，8461 名[11.9%]为其他或多种种族或族裔），5223 人出生于 1950 年至 1969 年，12226 人出生于 1970 年至 1979 年，22086 人出生于 1980 年至 1989 年，23894 人出生于 1990 年至 1999 年，7912 人出生于 2000 年至 2005 年。初潮年龄的平均值（SD）从 1950 年至 1969 年的 12.5（1.6）岁降至 2000 年至 2005 年的 11.9（1.5）岁。经历初潮提前的人数从 8.6%（449 人）增加到 15.5%（1223 人），经历极早潮的人数从 0.6%（31 人）增加到 1.4%（110 人），经历晚潮的人数从 5.5%（286 人）减少到 1.7%（137 人）。对于 61932 名报告了规律时间的参与者，在 2 年内达到规律的人数从 76.3%（3463 人）降至 56.0%（4075 人），尚未进入规律周期的人数从 3.4%（153 人）增加到 18.9%（1375 人）。初潮提前的趋势在自我认定为亚裔、非西班牙裔黑人或其他或多种族裔（而非非西班牙裔白人）的参与者中（交互作用 P = 0.003）和自我评定社会经济地位较低的参与者中（交互作用 P < 0.001）更为明显。在有初潮 BMI 数据的 9865 名参与者的一个亚组中，探索性中介分析估计，初潮年龄的时间趋势有 46%（95%CI，35%-61%）可以用 BMI 来解释。
在这项对美国 71341 名个体的队列研究中，随着出生年份的增加，初潮年龄下降，规律时间增加。这些趋势在少数族裔和社会经济地位自评较低的个体中更为明显。这些趋势可能导致美国不良健康结果和差异的增加。
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