Relation between 20-year income volatility and brain health in midlife: the CARDIA study

Objective: Income volatility presents a growing public health threat. To our knowledge, no previous study examined the relationship between income volatility, cognitive function and brain integrity.
Methods: We studied 3,287 participants aged 23 to 35 years in 1990 from the Coronary Artery Risk Development in Young Adults prospective cohort study. Income volatility data were created using income data collected from 1990 to 2010 and defined as standard deviation of percent change in income and number of income drops >=25% (categorized as 0, 1, or 2+). In 2010, cognitive tests (n=3,287) and brain scans (n=716) were obtained.
Results: After covariate adjustment, higher income volatility was associated with worse performances on processing speed (β=-1.09, 95%CI=-1.73, -0.44) and executive functioning (β=2.53, 95%CI:0.60, 4.50) but not on verbal memory (β=-0.02, 95%CI:-0.16, 0.11). Similarly, additional income drops were associated with worse performances on processing speed and executive functioning. Higher income volatility and more income drops were also associated with worse microstructural integrity of total brain and total white matter. All findings were similar when restricted to those with high education, suggesting reverse causation may not explain these findings.
Conclusion: Income volatility over a 20-year period of formative earning years was associated with worse cognitive function and brain integrity in midlife.

研究目的：收入波动已成为日益严峻的公共健康威胁。据我们所知，此前尚无研究探讨收入波动、认知功能与大脑完整性之间的关联。
研究方法：我们基于青年冠状动脉风险发展（Coronary Artery Risk Development in Young Adults, CARDIA）前瞻性队列研究，纳入1990年招募的3287名年龄介于23至35岁的参与者。收入波动数据通过1990年至2010年采集的收入信息构建，定义为收入百分比变化的标准差以及收入降幅≥25%的次数（分为0次、1次或2次及以上三类）。2010年，我们对全部3287名参与者开展了认知测试，并对其中716名参与者进行了脑部扫描。
研究结果：经协变量校正后，较高的收入波动与更差的处理速度（β=-1.09，95%置信区间：-1.73~-0.44）和执行功能（β=2.53，95%置信区间：0.60~4.50）表现相关，但与言语记忆无显著关联（β=-0.02，95%置信区间：-0.16~0.11）。类似地，收入降幅次数更多也与更差的处理速度和执行功能表现相关。更高的收入波动与更多的收入降幅同时也与全脑及全白质的微结构完整性受损相关。将分析限定在高学历人群时，所有结果均保持一致，提示反向因果关系可能无法解释上述发现。
研究结论：在20年的收入形成期内的收入波动，与中年时期更差的认知功能及大脑完整性相关。