本研究使用臺灣出生世代研究的調查資料進行分析，探討兒童時期洗手習慣類型及其對新冠肺炎疫情下青少年健康狀況的影響。分析樣本為在自變項與依變項皆無遺漏值者，共計17,996名青少年。本結果顯示，近八成的青少年在疫情期間之健康狀況為「好」。另外，70.73%的樣本在5.5歲時有洗手習慣；8歲時有洗手習慣者則高達92.04%。長期而言，兒童時期的洗手習慣有四類：「早期養成（66.93%）」、「晚期養成（25.11%）」、「習慣消退（3.08%）」及「不曾養成（4.17%）」。控制社會人口學特性與5.5歲時的健康狀況後發現，洗手習慣類型與青少年疫情期間之健康狀況的關係具劑量效應關係；相較「早期養成」組，洗手習慣類型為「晚期養成」或「不曾養成」之青少年，在疫情期間有良好健康狀況的可能性較低，且以「不曾養成」對健康的負面影響更大。綜合而言，本研究結果發現，兒童時期之洗手習慣對後續健康的重要性。建議政府持續推廣並發展有效的衛生教育及介入措施，協助兒童建立良好洗手習慣，以促進健康。

The coronavirus disease 2019 (COVID–19) pandemic attributable to infection with SARS-CoV–2 has emerged as a global public health challenge. The most recent data show that there have been over 5 billion confirmed cases and more than 6 million deaths world-wide as of the end of April 2022. In response to COVID–19, the World Health Organization and Centers for Disease Control and Prevention have recommended that the public implement preventive strategies, including handwashing, to reduce SARS-CoV–2 transmission and the associated long-term sequelae. The long-term association between handwashing habits and adolescent health status during the pandemic, however, has never been examined. This study used data from the Taiwan Birth Cohort Study (TBCS) to investigate the patterns of handwashing habits during childhood and the subsequent influences on adolescent health status during the COVID–19 pandemic. TBCS is the first nationwide representative study of children in Taiwan that aimed to investigate the trajectories of children’s health and examine factors that contribute to their health development. By 2020, ten waves of the survey had been completed when children were at 6 months, 18 months, 3 years, 5.5, 7, 8, 9, 12, 13, and 15 years of age. The response rates of each wave ranged from 87.8% to 94.9%. A total of 17,996 participants who completed the 5.5-year, 8-year, and 15-year surveys and had no missing values on focal study variables were included for the current analysis. The study results show that about 80% of adolescents had good health status during the COVID–19 pandemic. Additionally, the rates of handwashing habits among children were 70.73% at five years old and increased to 92.0% at eight years old. Based on data of hand-washing habits collected in the 5.5-year and 8-year surveys, we further identified four patterns of handwashing habits during childhood, namely “early formation (66.93%),” “late formation (25.11%), “arrested formation (3.08%),” and “non-formation (4.17%).” After controlling for sociodemographic factors and health status at five years old, we found significant associations between patterns of handwashing habits and health status during the COVID–19 pandemic. Specifically, the odds ratio (OR) of having good health status during the COVID–19 pandemic was significantly lower among adolescents who had “late formation” (OR=0.79, 95% CI=0.72–0.86) or “non-formation” (OR=0.69, 95% CI =0.58 –0.82) patterns of handwashing habits during childhood than those with the “early formation” pattern, with the negative effects on health status being most evident for those with the “non-formation” pattern. Sensitivity analyses were further conducted to test whether different classifications for the patterns of handwashing habits would influence study results. Similar results were obtained when we combined “late formation” and “arrested formation” into “inconsistent formation.” That is, com-pared to adolescents who had an “early formation” pattern of hand-washing habits during childhood, those had “inconsistent formation” and “non-formation” patterns were less likely to have good health status during the COVID–19 pandemic. Our findings highlight the importance and the long-term effects of childhood handwashing habits on health status among adolescents. The government should continue developing and implementing effective handwashing interventions to help promote health. Future studies could link TBCS data with the National Health Insurance Research Database to further understand the benefits of handwashing on dis-ease mortality and health care utilization. More research is also needed to investigate factors associated with handwashing habits and the underlying mechanisms linking handwashing habits and health.