ImportanceHuman brain development and maintenance is under both genetic and environmental influences that likely affect later-life dementia risk.ObjectiveTo examine environmental influences by testing whether time-dependent secular differences occurred in cranial and brain volumes and cortical thickness over birth decades spanning 1930 to 1970.Design, Setting, and ParticipantsThis cross-sectional study used data from the community-based Framingham Heart Study cohort for participants born in the decades 1930 to 1970. Participants did not have dementia or history of stroke and had magnetic resonance imaging (MRI) obtained from March 18, 1999, to November 15, 2019. The final analysis dataset was created in October 2023.ExposureYears of birth ranging from 1925 to 1968.Main MeasuresCross-sectional analysis of intracranial, cortical gray matter, white matter, and hippocampal volumes as well as cortical surface area and cortical thickness. The secular measure was the decade in which the participant was born. Covariates included age at MRI and sex.ResultsThe main study cohort consisted of 3226 participants with a mean (SD) age of 57.7 (7.8) years at the time of their MRI. A total of 1706 participants were female (53%) and 1520 (47%) were male. The birth decades ranged from the 1930s to 1970s. Significant trends for larger intracranial, hippocampal, and white matter volumes and cortical surface area were associated with progressive birth decades. Comparing the 1930s birth decade to the 1970s accounted for a 6.6% greater volume (1234 mL; 95% CI, 1220-1248, vs 1321 mL; 95% CI, 1301-1341) for ICV, 7.7% greater volume (441.9 mL; 95% CI, 435.2-448.5, vs 476.3 mL; 95% CI, 467.0-485.7) for white matter, 5.7% greater value (6.51 mL; 95% CI, 6.42-6.60, vs 6.89 mL; 95% CI, 6.77-7.02) for hippocampal volume, and a 14.9% greater value (1933 cm2; 95% CI, 1908-1959, vs 2222 cm2; 95% CI, 2186-2259) for cortical surface area. Repeat analysis applied to a subgroup of 1145 individuals of similar age range born in the 1940s (mean [SD] age, 60.0 [2.8] years) and 1950s (mean [SD] age, 59.0 [2.8] years) resulted in similar findings.Conclusion and RelevanceIn this study, secular trends for larger brain volumes suggested improved brain development among individuals born between 1930 and 1970. Early life environmental influences may explain these results and contribute to the declining dementia incidence previously reported in the Framingham Heart Study cohort.

中文翻译：

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1930 年至 1970 年出生的弗雷明汉心脏研究参与者的颅内和脑容量趋势

重要性人类大脑的发育和维护受到遗传和环境的影响，可能会影响晚年痴呆的风险。目的通过测试 1930 年至 1970 年出生的几十年间颅骨和大脑体积以及皮质厚度是否存在随时间变化的长期差异，来检查环境影响。设计、设置和参与者这项横断面研究使用了基于社区的弗雷明汉心脏研究队列的数据，该队列针对 1930 年至 1970 年出生的参与者。参与者没有痴呆症或中风病史，并进行了磁共振成像 (MRI) 1999年3月18日至2019年11月15日。最终分析数据集创建于2023年10月。暴露出生年份范围为1925年至1968年。主要指标颅内、皮质灰质、白质和海马体积的横断面分析如皮质表面积和皮质厚度。世俗衡量标准是参与者出生的十年。协变量包括 MRI 年龄和性别。结果主要研究队列由 3226 名参与者组成，MRI 时平均 (SD) 年龄为 57.7 (7.8) 岁。共有 1706 名参与者为女性（53%），1520 名参与者（47%）为男性。出生年代从 20 世纪 30 年代到 1970 年代。颅内、海马、白质体积和皮质表面积增大的显着趋势与连续出生数十年相关。将 1930 年代出生的十年与 1970 年代相比，ICV 容量增加了 6.6%（1234 mL；95% CI，1220-1248 vs 1321 mL；95% CI，1301-1341），ICV 容量增加了 7.7%（441.9 mL；95% CI，1301-1341）。白质的 95% CI，435.2-448.5 vs 476.3 mL；95% CI，467.0-485.7），值高出 5.7%（6.51 mL；95% CI，6.42-6.60 vs 6.89 mL；95% CI，6.77- 7.02）海马体积，值增加了 14.9%（1933 cm2; 95% CI，1908-1959 年，对比 2222 厘米2; 95% CI, 2186-2259) 皮质表面积。对出生于 1940 年代（平均 [SD] 年龄，60.0 [2.8] 岁）和 1950 年代（平均 [SD] 年龄，59.0 [2.8] 岁）的 1145 名年龄范围相似的个体进行重复分析，得出了类似的结果。结论和相关性在这项研究中，大脑体积增大的长期趋势表明，1930 年至 1970 年之间出生的个体的大脑发育有所改善。早期生活环境的影响可以解释这些结果，并有助于先前在弗雷明汉心脏研究队列中报告的痴呆发病率下降。