21Objectives: This study aims to estimate the losses of quality-adjusted life expectancy (QALE) due to the 22 joint effect of cognitive impairment and multimorbidity, and further to confirm additional losses 23 attributable to their interaction among the middle-aged and elderly Chinese. 24 Methods: The National Cause of Death Monitoring Data were linked with the China Health and 25 Retirement Longitudinal Study (CHARLS). A mapping and assigning method was used to estimate 26health utility values, which were further used to calculate QALE. Losses of QALE were measured by 27 comparing the differences between subgroups. And all the losses of QALE were displayed at two levels:28 the individual and the population level. 29Results: At age 45, the individual-level and population-level losses of QALE (95% CI) attributed to the 30 combination of cognitive impairment and multimorbidity were 7. 606 (5.679, 9.566) years and 4.297 31 (3.425, 5.200) years. The losses (95% CI) for cognitive impairment alone were 3.104 (2.287, 3.954) years 32 and 1.709 (1.318, 2.132) years at two levels. Similarly, the losses (95% CI) for multimorbidity alone 33 were 3.526 (2.528, 4.556) years and 1.914 (1.235, 2.625) years at two levels. Additional losses due to34 their interaction were indicated by the 0.976 years of the individual-level gap and 0.674 years of the 35 population-level gap.36 Conclusion: Among the middle-aged and elderly Chinese, cognitive impairment and multimorbidity 37 resulted in much losses of QALE, and additional QALE losses were seen due to their interaction at both 38 individual and population levels.39 40 3 Introduction 41 Age-associated cognitive impairment is a transition link between healthy aging and dementia with 42 the 10% conversion rate, featuring declines in memory, attention, and cognitive function [1]. At the end 43 of 2019, the population aged 65 and above in China accounted for 176.0 million [2]. And a large-sample, 44multi-region study showed that the prevalence (95% CI) of total dementia for the population aged 65 45 years and older in China was 5.60% (3.50%, 7.60%) in 2019 [3]. Moreover, mild cognitive impairment 46 (MCI) is estimated >4 times more common than dementia [1, 4]. 47Meanwhile, age-dependent noncommunicable diseases (NCD) are proved to experience a 48 continuous increase among the elders in the near decades [5]. Nearly 50% of the NCD burden in China 49 occurred in people aged 65 years and older [6], while 47.5% of the elderly aged 65+ had ≥ 2 chronic 50 conditions [7]. Multimorbidity, which is defined as the co-occurrence of two or more chronic diseases in 51 an individual, is widely observed beyond two-thirds of older adults [8, 9]. Many patient-based studies 52 suggested that older adults with at least two diseases were more susceptible to develop cognitive 53 impairment [10][11][12][13][14][15][16][17][18]. The hypothesis that multimorbidity may increase the risk of cognitive impairment 54 has also been verified in population-based researches [10][11][12] 14]. 55Despite the documented ris...