Bipolar Disorder (BD) alternates depressive, manic or hypomanic phases. A manic episode (ME) is the main psychopathological condition of BD and it often requires hospitalization. Air pollution is thought to play a role in onset and exacerbation of several psychiatric disorders. We aimed to verify the association between exposure to particulate matter ≤10 μm (PM10) and ME severity, assessed through the Young Mania Rating Scale (YMRS).

We evaluated clinical records regarding 414 hospital admissions of 186 patients residing in Milan (Italy), hospitalized for ME in the Psychiatry Unit of the Policlinico Hospital from 2007 to 2019. Patients were assigned mean daily PM10 and apparent temperature levels of the Milan municipality. As exposure windows, we considered single days preceding hospitalization (lag0 to 7) and their average estimates (lag0-1 to 0-7). We applied mixed effect models, adjusted for relevant confounders.

Short-term PM10 exposure was associated with a reduction in YMRS, both when considering daily lags [β: −0.43 (95% Confidence Interval: −0.83; −0.03) at lag0] and their average [−0.47 (−0.90; −0.04) at lag0-1]. YMRS was higher in psychotic patients (24.8) and lower in ME with mixed components (15.5) if compared to episodes characterized by neither mixed nor psychotic features (17.4, p < 0.001). While PM10 did not influence the risk of psychotic symptoms at admission, it was associated with a higher risk of ME with mixed features, with Odds Ratios ranging from 2.43 (1.02; 5.76) at lag0 to 3.60 (1.22; 10.7) at lag0-2.

Our findings show that increasing levels of PM10 move the ME towards the depressive pole of the BD spectrum and augment the probability of hospitalization for ME with mixed components. These results have important clinical implications, as mixed features worsen the course of ME and make the management of bipolar patients challenging.

双相情感障碍 (BD) 交替出现抑郁、躁狂或轻躁狂阶段。躁狂发作 (ME) 是 BD 的主要精神病理学状况，通常需要住院治疗。空气污染被认为在几种精神疾病的发作和恶化中起作用。我们旨在验证暴露于≤10 μm (PM10) 的颗粒物与 ME 严重程度之间的关联，通过年轻躁狂评定量表 (YMRS) 进行评估。

我们评估了 2007 年至 2019 年居住在米兰（意大利）的 186 名患者的 414 次住院记录，这些患者在 Policlinico 医院精神病科住院治疗。患者被分配了米兰市的每日平均 PM10 和表观温度水平。作为暴露窗口，我们考虑了住院前的单日（lag0 到 7）及其平均估计值（lag0-1 到 0-7）。我们应用了混合效应模型，并针对相关混杂因素进行了调整。

短期 PM10 暴露与 YMRS 降低相关，无论是在考虑每日滞后 [β：-0.43（95% 置信区间：-0.83；-0.03）在 lag0] 及其平均值 [-0.47（-0.90；-0.04）时) 在 lag0-1]。与既没有混合也没有精神病特征的发作相比，精神病患者的 YMRS 较高（24.8），而混合成分的 ME 较低（15.5）（17.4，p < 0.001）。虽然 PM10 不影响入院时出现精神病症状的风险，但它与具有混合特征的 ME 风险较高相关，优势比范围从 lag0 的 2.43 (1.02; 5.76) 到 lag0-2 的 3.60 (1.22; 10.7) .

我们的研究结果表明，PM10 水平的增加使 ME 向 BD 频谱的抑郁极移动，并增加了混合成分 ME 住院的可能性。这些结果具有重要的临床意义，因为混合特征会使 ME 病程恶化并使双相情感障碍患者的管理具有挑战性。