本文探討疫情前的網路使用是否有助於中老年人在預防行為、認知功能、身心健康與生活福祉等方面因應COVID-19 疫情。本研究採用CHARLS 2018 及2020 兩波追蹤資料，透過家戶固定效果模型比較同住夫妻間的差異。研究結果顯示，疫情前的網路使用讓女性在疫情期間更積極採取預防行為，男性則未見相應的提升，因而縮小了原有的性別差距，且此效果集中於農村樣本；相較之下，網路使用對認知功能與其他健康面向的影響則較不明確，且會隨衡量方式而異。我們發現社會資本對預防行為的作用在網路使用者與非使用者之間具有異質性，其效益主要集中在未使用網路者，顯示當缺乏網路時，線下社交網絡可能成為替代性的資訊管道。為建立疫情前網路使用的因果效果，本文採控制函數法，以2018 年城市層級網路使用率分別與1984 年城市電話密度、2017年各省寬頻下載速度兩項歷史通訊基礎設施的交乘項作為兩個工具變數；所得結果與家戶固定效果OLS 的主要結論一致。整體而言，疫情前的網路使用是中老年女性、尤其農村女性採取預防行為的重要資源，而社會資本則為未使用網路者提供替代管道。

This paper examines whether pre-pandemic internet use affected how middle-aged and older Chinese adults adapted to the COVID-19 pandemic in their preventive behavior, cognitive function, physical and mental health, and well-being. Using panel data from the 2018 and 2020 waves of CHARLS and household fixed-effects regressions that compare co-residing partners, we find that pre-pandemic internet use is associated with greater adoption of pandemic-period preventive behavior among women but not men, narrowing the pre-existing gender gap, a pattern concentrated in rural areas. By contrast, theevidence for cognitive function and broader health outcomes is less consistent and varies with how outcomes are measured. The association between social capital and preventive behavior is heterogeneous by internet use status and concentrated among non-users, consistent with offline social networks substituting for the internet as an information channel when digital access is absent. To establish the causal effect of pre-pandemic internet use, we adopt a control-function approach with two instruments, each interacting the 2018 city-level internet use rate of other individuals with a historical measure of communication infrastructure, namely 1984 city-level telephone density and 2017 provincial broadband download speed. The resulting estimates are consistent with the household fixed-effects OLS conclusions. Overall, pre-pandemic internet use was an important behavioral resource for older women, especially in rural areas, while offline social capital provided a substitute channel for those without internet access.

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