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J Health Info Stat > Volume 48(1); 2023 > Article
성인 암 생존자의 자가보고된 기억력 문제에 대한 관련요인 분석: 2019 국민건강영양조사자료

Abstract

Objectives

With the development of treatment technology, the percentage of cancer survivors has continued to increase. However, the cognitive decline these patients experience has been overlooked because it is not related to survival. This study investigated factors related to memory problems in patients with cancer.

Methods

Using data from the 2019 Korea National Health and Nutrition Examination Survey (KNHANES), this secondary data analysis study attempted to identify factors related to memory problems in cancer survivors. Of the 8,110 survey participants, there were 6,296 adults, aged 19 years or older. Of these, 357 were diagnosed with cancer. Four participants were excluded due to missing values for occupation, income, and body mass index (BMI). Finally, 353 subjects were included in the research analysis. The data were statistically analyzed using IBM SPSS version 28.0.

Results

218 (61.8%) of the cancer survivors reported memory problems. Having a lower-than-average individual income (odds ratio, OR=2.16, 95% confidence interval, CI=1.31-3.53, p = 0.003), smoking (OR=3.19, 95% CI=1.16-8.72, p = 0.024), and depression (OR=6.06, 95% CI=1.33-27.57, p = 0.020) were significant potentiating factors. In contrast, having a job (OR=0.18, 95% CI=0.05-0.67, p = 0.011), drinking (OR=0.26, 95% CI=0.09-0.81, p = 0.021), and walking three to four days per week (OR=0.15, 95% CI=0.03-0.81, p = 0.027) decreased memory problems.

Conclusions

Our findings suggest that it is necessary to develop cognitive rehabilitation programs for cancer survivors.

요약

목적

최근 치료기술의 발달로 암 생존자의 비율은 지속적으로 증가하고 있음에도 불구하고, 암 생존자가 경험하는 인지기능저하는 생존과 관련이 없어 상대적으로 간과되어 왔다. 따라서 본 연구에서는 암 생존자의 기억력 문제와 관련된 요인을 조사하기 위하여 시도되었다.

방법

본 연구는 2019년 국민건강영양조사 자료를 이용한 2차자료 분석연구이다. 조사 대상자 8,110명 중 19세 이상 성인은 6,296명이었고, 이 중 357명이 암 진단 경험이 있었다. 4명의 참가자는 직업, 소득 및 체질량 지수의 결측값이 있어 제외한 후, 353명의 자료를 SPSS 28.0 프로그램을 사용하여 통계적으로 분석하였다.

결과

암 생존자 중 218명(61.8%)이 기억력 문제를 보고하였다. 중앙값 이하의 개인소득(odds ratio, OR=2.16, 95% confidence interval, CI=1.31-3.53, p = 0.003), 흡연(OR=3.19, 95% CI=1.16-8.72, p = 0.024), 우울증(OR=6.06, 95% CI=1.33-27.57, p = 0.020)은 유의한 높은 기억력 문제와 관련된 요인이었다. 반면, 직업(OR=0.18, 95% CI=0.05-0.67, p = 0.011), 음주(OR=0.26, 95% CI=0.09-0.81, p = 0.021), 주당 3-4일 걷기(OR=0.15, 95% CI=0.03-0.81, p = 0.027)는 낮은 기억력 문제와 관련된 요인이었다.

결론

본 연구결과를 토대로 암 생존자의 기억력 문제와 관련된 요인을 교정할 수 있는 인지 재활 프로그램 개발이 필요하다.

INTRODUCTION

Although the number of cancer patients in Korea has increased from 218,000 (2015) to 255,000 (2019) [1], the survival rate has also increased due to advances in early detection and cancer treatment [2]. As of 2019, the survival rate of cancer patients over the past five years was 70.7% [1].
The term, cancer survivor, was first used by a pediatrician, Fitzhugh Mullan, in 1975 and has various definitions, depending on the literature [3]. In general, a cancer survivor refers to “ an individual from the time of cancer diagnosis through the balance of his or her life” [4]. After treatment, cancer survivors generally live a normal life of high quality [2,5]. However, most of these patients experience temporary or permanent late effects [2,6]. The late effects of cancer and cancer treatment involve physical symptoms, such as pain and neuropathy, and psychosocial problems including anxiety, depression, and cognitive impairment [7].
Cancer-related cognitive impairment refers mainly to memory lapses or difficulty concentrating [6], and can also be associated with impairments in learning, executive function, and processing speed [8]. Cancer-related cognitive impairment is known to be an adverse effect of chemotherapy [8], and therefore, is also known as chemotherapy-related cognitive impairment, chemo brain, or chemo fog [6]. However, some cancer survivors complained of cognitive impairment even though they did not receive chemotherapy [6]. Furthermore, some rodent trials have shown cognitive and behavioral changes before chemotherapy for cancer [9].
The tumor, sociodemographic or genetic factors, treatment, physiological problems, and lifestyle can all affect cognitive changes in cancer survivors [10]. Most studies on cognitive impairment conducted in South Korea have focused on the relationship between cognitive changes and chemotherapy [11-13] or in patients with breast cancer [12,13]. This study aimed to investigate the factors related to memory problems in individuals who were diagnosed with cancer, using the Korea National Health and Nutrition Examination Survey (KNHANES). Considering the results, the development of cognitive rehabilitation programs for cancer survivors was also discussed.

METHODS

Study design

This is a cross-sectional study using secondary data analysis. Using data from the 2019 KNHANES (a government-designated statistical database under the National Health Promotion Act), the study attempted to identify factors related to memory problems in cancer survivors.

Sample

The study sample included 353 adult cancer survivors who were enrolled in the 2019 KNHANES. Of the 8,110 participants in this study, there were 6,296 adults, aged 19 years or older. Of these, 357 were diagnosed with cancer including stomach, liver, colorectal, breast, cervical, lung, thyroid, and other cancers. Four patients were excluded due to missing values for occupation, income, and body mass index (BMI). A total of 353 individuals were included in the final analysis.

Instruments

Measurements included general characteristics and factors related to health, such as health behaviors, psychological health, and physical health.

General characteristics

The study considered the following general characteristics: gender, age, education level, marital status, job, living alone status, and income. Gender was classified as male and female. Age was divided into young adults under the age of 40 years, middle age over 40 years old, older adults under 65 years of age, and elderly adults older than 65 years of age. Education level was divided into over high school and below middle school level. Marital status, job status, and living status were classified according to presence or absence. Income was divided into individuals’ quartile incomes above and below the median.

Health characteristics

Health behaviors including drinking, smoking, sleep duration, activity restriction, walking, and strength exercises were considered. Drinking was classified according to whether drinking occurred during the past year and smoking was classified as smoking or non-smoking. Sleep duration was classified as an average daily sleep time of less than 6 hours, 7 to 8 hours, and 9 hours or more. Activity restrictions were classified according to current activity status. For physical activities, walking and strength exercises were classified as the number of days per week (5-7 days, 3-4 days, 1-2 days, and no exercise).
Psychological health was considered in terms of depression, stress, and patient-perceived health status. Depression was classified as present or absent, depending on whether the person had experienced depression for at least two consecutive weeks in the past year. Stress was categorized into rarely, somewhat, much, and a great deal, depending on the level of stress experienced in daily life. Perceived health status was reclassified as bad (including very bad and bad, neutral (or average), and good (including good and very good), depending on the patient's self-perception of their health.
Physical health factors considered in this study included BMI, hypertension, diabetes mellitus, and dyslipidemia. BMI (kg/m2) was considered, and participants were classified as obese (BMI was more than 25), overweight (BMI between 23-25), normal (BMI between 18.5 and 23), and underweight (BMI less than 18.5). Hypertension, diabetes, and dyslipidemia were classified according to presence or absence.

Memory problems

The dependent variable, memory problems, was defined as the participant's memory status during the past week. Participants who responded that they had no memory difficulty at all was classified as having “ no memory problems”. In contrast, participants who expressed occasional memory difficulties were classified as having “ some memory problems”, while those who responded that they experienced frequent trouble remembering things were classified as having “ extreme memory problems”.

Data collection

The sampling frame included data from the 2016 population and housing census, while the stratification variables were obtained from the administrative division and housing type. Facilities, such as nursing homes, the military, prisons, and foreign households, were excluded from the sample survey frame. From the rolling sampling over 12 months, 8,110 individuals from 3,670 households participated in the survey.

Data analysis

The complex survey data were analyzed using SPSS 28.0 (IBM Corp., Armonk, NY, USA), according to the KNHANES guidelines of the Korea Disease Control and Prevention Agency (KCDC). Statistically, p-values of greater than 0.05 were considered significant. First, both unweighted and weighted frequencies were presented through a descriptive statistical analysis of the participant characteristics. Second, a chisquare test for complex survey data was conducted to analyze the level of memory problems according to general and health characteristics. Finally, a multivariable multinomial logistic regression analysis was performed to analyze the factors related to memory problems.

Ethical considerations

The investigation in the first year (2019) of the 8th period was conducted after the approval of the IRB due to the collection of human materials and the disclosure of raw data (2018-01-03-C-A). This study was conducted with the approval of the IRB of University of Ulsan (IRB No.: 2022R0020).

RESULTS

Characteristics of the cancer survivors

The participants of this study included 353 cancer survivors. Of these, 135 (38.2%) participants indicated that they had no memory problems, 191 (54.1%) responded that they experienced memory problems sometimes, 25 (7.1%) had memory problems often, and 2 (0.6%) experienced constant memory problems. Most participants had a diagnosis of other cancers (93, 25.2%). In contrast, few participants were diagnosed with liver cancer (5, 1.4%) (Table 1).
Table 1.
Characteristics of the cancer survivors (n=353, weighted n=1,934,029)
Characteristics Categories n (%) Weighted n (%) SE 95% CI
Lower Upper
Memory problems Never 135 (38.2) 789,122 (40.8) 80,101 930,618 947,627
Sometimes 191 (54.1) 1,040,381 (53.8) 79,027 884,001 1,196,760
Often 25 (7.1) 95,267 (4.9) 21,759 52,210 138,324
Always 2 (0.6) 9,259 (0.5) 7,052 -4,696 23,213
Cancer type1 Stomach 54 (14.6) 265,335 (13.7) 41,471 183,271 347,340
Liver 5 (1.4) 41,084 (2.1) 19,642 2,216 79,952
Colorectal 44 (11.9) 233,859 (12.1) 39,897 154,910 312,808
Breast 59 (16.0) 340,389 (17.6) 52,039 237,414 443,364
Cervical 21 (5.7) 112,715 (5.8) 27,922 57,463 167,968
Lung 18 (4.9) 85,308 (4.4) 23,549 38,708 131,908
Thyroid 75 (20.3) 477,826 (24.7) 63,487 352,198 603,455
Other 93 (25.2) 484,621 (25.1) 64,571 356,846 612,396

SE, standard error; CI, confidence interval.

1 Possible duplicate answers.

Demographic characteristics of the cancer survivors

Of the demographic characteristics considered, job (p = 0.008) and income (p = 0.008) were most significantly associated with memory problems among the three groups. However, there were no statistically significant differences with gender (p = 0.241), age (p = 0.279), education level (p = 0.196), marital status (p = 0.948), and living alone status (p = 0.461) (Table 2).
Table 2.
Demographic characteristics of the cancer survivors (n1=353, N2=1,934,029)
Characteristics Categories Total Memory problems χ2 p
No
(n1 = 135, N2 = 789,122)
Sombre
(n1 = 191, N2 = 1,040,380)
Extreme
(n1 = 27, N2 = 104,525)
n (%) n (%) Weighted
n (%)
n (%) Weighted
n (%)
n (%) Weighted
n (%)
Gender Men 144 (40.8) 58 (40.3) 322,197 (16.7) 73 (50.7) 378,087 (19.5) 13 (9.0) 57,247 (3.0) 2.75 0.241
Women 209 (59.2) 77 (36.8) 466,926 (24.1) 118 (56.5) 662,294 (34.2) 14 (6.7) 47,278 (2.4)
Age (y) 19-39 16 (4.5) 10 (62.5) 64,216 (3.3) 6 (37.5) 49,012 (21.3) 0 (0.0) 0 (0.0) 7.28 0.279
40-65 168 (47.6) 64 (38.1) 431,073 (22.3) 98 (58.3) 579,623 (19.5) 6 (3.6) 37,131 (1.9)
≥65 169 (47.9) 61 (36.1) 293,834 (15.2) 87 (51.5) 411,746 (34.2) 21 (12.4) 67,394 (3.5)
Education level ≤Middle school 147 (41.6) 50 (34.0) 252,614 (13.1) 79 (53.7) 375,665 (30.0) 18 (12.3) 57,063 (3.0) 3.84 0.196
≥High school 206 (58.4) 85 (41.2) 536,508 (27.7) 112 (54.4) 664,716 (34.4) 9 (4.4) 47,462 (2.5)
Marital status With spouse 273 (77.3) 106 (38.8) 609,055 (31.5) 146 (53.5) 814,557 (42.1) 21 (7.7) 83,574 (4.3) 0.11 0.948
Without spouse 80 (22.7) 29 (36.3) 180,068 (9.3) 45 (56.2) 225,824 (11.7) 6 (7.5) 20,951 (1.1)
Job Yes 146 (41.4) 67 (45.9) 397,337 (20.5) 75 (51.4) 418,696 (21.6) 4 (2.7) 13,848 (0.7) 10.66 0.008*
No 207 (58.6) 68 (32.9) 391,785 (20.3) 116 (56.0) 621,684 (32.1) 23 (11.1) 90,677 (4.7)
Living alone status Yes 313 (88.7) 124 (39.6) 742,053 (38.4) 165 (52.7) 947,815 (49.0) 24 (7.7) 91,178 (4.7) 1.62 0.461
No 40 (11.3) 11 (27.5) 47,070 (2.4) 26 (65.0) 92,566 (4.8) 3 (7.5) 13,347 (0.7)
Income Lower-than-median 165 (46.7) 49 (29.7) 285,877 (14.8) 101 (61.2) 563,551 (29.1) 15 (9.1) 57,572 (3.0) 11.13 0.008*
Higher-than-median 188 (53.3) 86 (45.7) 503,245 (26.0) 90 (47.9) 476,830 (24.7) 12 (6.4) 46,953 (2.4)

1 Unweighted sample size.

2 Weighted sample size.

* p <0.05.

Health characteristics of the cancer survivors

Of the health characteristics examined, drinking (p = 0.033), smoking (p = 0.040), and walking (p = 0.023) were the most significant health behaviors associated with memory problems among the three groups. Regarding psychological health, depression (p = 0.002), stress (p <0.001) and self-perceived health status (p = 0.042) were the most significant variables. Interestingly, for physical health, there were no statistically significant differences (Table 3).
Table 3.
Characteristics related to health of the cancer survivors (n1=353, N2=1,934,029)
Characteristics Categories Total Memory loss χ2 p
No
(n1 = 135, N2 = 789,122)
Some
(n1 = 191, N2 = 1,040,380)
Extreme
(n1 = 27, N2 = 104,525)
n (%) n (%) Weighted
n (%)
n (%) Weighted
n (%)
n (%) Weighted
n (%)
Health behaviors
Drinking Yes 175 (49.6) 67 (38.3) 403,000 (41.2) 103 (58.9) 553,835 (56.6) 5 (2.8) 22,307 (2.3) 7.07 0.033*
No 178 (50.4) 68 (38.2) 386,123 (40.4) 88 (49.4) 486,546 (51.0) 22 (12.4) 82,218 (8.6)
Smoking Yes 139 (39.4) 48 (34.5) 268,032 (13.9) 76 (54.7) 383,809 (19.8) 15 (10.8) 67,976 (3.5) 6.98 0.040*
No 214 (60.6) 87 (40.7) 521,090 (26.9) 115 (53.7) 656,572 (33.9) 12 (5.6) 36,549 (1.9)
Sleep duration (hours) Deprived sleep (≤6) 156 (44.3) 52 (33.3) 275,012 (33.0) 94 (60.3) 515,091 (61.8) 10 (6.4) 43,476 (5.2) 9.94 0.070
7-8 170 (48.3) 72 (42.4) 468,627 (47.8) 86 (50.6) 466,210 (47.6) 12 (7.1) 43,850 (4.5)
≥9 26 (7.4) 11 (42.3) 45,483 (38.1) 11 (42.3) 59,080 (49.5) 4 (15.4) 14,806 (12.4)
Activity restriction Yes 52 (14.7) 17 (32.7) 102,989 (5.3) 24 (46.2) 107,609 (5.6) 11 (21.1) 34,924 (1.8) 8.35 0.055
No 301 (85.3) 118 (39.2) 686,134 (35.5) 167 (55.5) 932,772 (48.2) 16 (5.3) 69,601 (3.6)
Walking (days per 1 week) 5-7 170 (48.2) 76 (44.7) 450,466 (23.3) 84 (49.4) 460,795 (23.8) 10 (5.9) 41,194 (2.1) 18.59 0.023*
3-4 82 (23.2) 24 (29.3) 149,126 (7.7) 55 (67.1) 319,622 (16.5) 3 (3.6) 8,829 (0.5)
1-2 43 (12.2) 14 (32.6) 72,520 (3.7) 25 (58.1) 127,520 (6.6) 4 (9.3) 13,895 (0.7)
Never 58 (16.4) 21 (36.2) 117,011 (6.1) 27 (46.6) 132,444 (6.8) 10 (17.2) 40,607 (2.1)
Strength exercises (days per 1 week) 5-7 30 (8.5) 15 (50.0) 92,563 (4.8) 13 (43.3) 60,153 (3.1) 2 (6.7) 4,414 (0.2) 8.58 0.237
3-4 29 (8.2) 8 (27.6) 48,096 (2.5) 20 (69.0) 101,695 (5.3) 1 (3.4) 7,496 (0.4)
1-2 24 (6.8) 7 (29.2) 41,396 (2.1) 16 (66.7) 97,507 (5.0) 1 (4.1) 1,372 (0.1)
Never 270 (76.5) 105 (38.9) 607,068 (31.4) 142 (52.6) 781,027 (40.4) 23 (8.5) 91,244 (4.7)
Psychosocial health
Depression Yes 47 (13.3) 9 (19.1) 47,341 (2.4) 28 (59.6) 142,150 (7.3) 10 (21.3) 39,495 (2.0) 17.62 0.002*
No 306 (86.7) 126 (41.2) 741,781 (38.4) 163 (53.3) 898,231 (46.4) 17 (5.5) 65,030 (3.4)
Stress Rarely 71 (20.1) 43 (60.6) 246,010 (12.7) 25 (35.2) 115,757 (6.0) 3 (4.2) 14,002 (0.7) 23.50 <0.001*
Somewhat 209 (59.2) 70 (33.5) 413,691 (21.4) 123 (58.9) 666,906 (34.5) 16 (7.6) 63,751 (3.3)
Much 60 (17.0) 18 (30.0) 108,770 (5.6) 37 (61.7) 233,278 (12.1) 5 (8.3) 20,100 (1.0)
A great deal 13 (3.7) 4 (30.8) 20,650 (1.1) 6 (46.1) 24,440 (1.3) 3 (23.1) 6,672 (0.3)
Perceived health status Bad 99 (28.0) 34 (34.3) 191,348 (9.9) 51 (51.6) 248,297 (12.8) 14 (14.1) 59,032 (3.1) 10.00 0.042*
Neutral 180 (51.0) 67 (37.2) 427,923 (22.1) 104 (57.8) 575,902 (29.8) 9 (5.0) 34,329 (1.8)
Good 74 (21.0) 34 (45.9) 169,851 (8.8) 36 (48.7) 216,182 (11.2) 4 (5.4) 11,164 (0.6)
Physical health
Body mass index Obesity 109 (30.9) 30 (27.5) 26,173 (1.4) 69 (63.3) 15,404 (0.8) 10 (9.2) 9,874 (0.5) 4.65 0.096
Overweight 82 (23.2) 34 (41.5) 193,980 (10.0) 45 (54.9) 36,607 (11.8) 3 (3.6) 6,570 (0.5)
Underweight 21 (5.9) 9 (42.9) 762,950 (39.4) 8 (38.1) 1 1,024,977 (53.0) 4 (19.0) 94,651 (4.9)
Normal 141 (39.9) 62 (44.0) 333,178 (17.2) 69 (48.9) 433,115 (22.4) 10 (7.1) 40,121 (2.1)
Hypertension Yes 130 (36.8) 46 (35.4) 265,530 (13.7) 74 (56.9) 381,131 (19.7) 10 (7.7) 34,808 (1.8) 0.35 0.830
No 223 (63.2) 89 (39.9) 523,593 (27.1) 117 (52.5) 659,250 (34.1) 17 (7.6) 69,717 (3.6)
Diabetes mellitus Yes 49 (13.9) 12 (24.5) 75,490 (3.9) 28 (57.1) 142,702 (7.4) 9 (18.4) 31,761 (1.6) 6.72 0.065
No 304 (86.1) 123 (40.5) 713,632 (36.9) 163 (53.6) 897,679 (46.4) 18 (5.9) 72,765 (3.8)
Dyslipidemia Yes 101 (28.6) 38 (37.6) 229,070 (11.8) 53 (52.5) 260,371 (13.5) 10 (9.9) 36,467 (1.9) 1.27 0.593
No 252 (71.4) 97 (38.5) 560,052 (29.0) 138 (54.8) 780,009 (40.3) 17 (6.7) 68,058 (3.5)

1 Unweighted sample size.

2 Weighted sample size.

* p <0.05.

Factors associated with memory problems among cancer survivors

The “ some memory problems” had a great risk by 2.16 times in participants with a lower-than-median income compared to those with higher-than-median incomes (OR=2.16, 95% CI=1.31-3.53, p = 0.003). The risk of “ extreme memory problems” decreased by 0.18 times among participants who have a job (OR=0.18, 95% CI=0.05-0.67, p = 0.011), 0.26 times among those who drink (OR=0.26, 95% CI=0.09-0.81, p = 0.021), and 0.15 times among those who walked 3 to 4 times per week (OR= 0.15, 95% CI=0.03-0.81, p = 0.027). However, the risk of “ extreme memory problems” increased by 3.19 times among participants who smoked (OR=3.19, 95% CI=1.16-8.72, p = 0.024) and 6.06 times among those with depression (OR=6.06, 95% CI=1.33-27.57, p = 0.020) (Table 4).
Table 4.
Multivariable multinomial logistic regression analysis of influencing factors to memory problems of the cancer survivors (n1=353, N2=1,934,029)
Characteristics Categories Memory problems
Some (reference, no)
(n1 = 191, N2 = 1,040,380)
Extreme (reference, no)
(n1 = 27, N2 = 104,525)
Adjusted OR 95% CI p Adjusted OR 95% CI p
Job Yes 0.59 0.34-1.04 0.066 0.18 0.05-0.67 0.011*
No 1.00 1.00
Income (individual) Lower-than-median 2.16 1.31-3.53 0.003* 1.68 0.56-5.08 0.353
Higher-than-median 1.00 1.00
Drinking Yes 1.18 0.69-2.01 0.545 0.26 0.09-0.81 0.021*
No 1.00 1.00
Smoking Yes 1.20 0.73-1.96 0.465 3.19 1.16-8.72 0.024*
No 1.00 1.00
Walking (days per 1 week) 5-7 0.84 0.36-1.96 0.680 0.30 0.07-1.33 0.112
3-4 1.50 0.56-4.05 0.420 0.15 0.03-0.81 0.027*
1-2 1.95 0.70-5.40 0.199 0.64 0.08-5.05 0.671
Never 1.00 1.00
Depression Yes 1.95 0.68-5.59 0.212 6.06 1.33-27.57 0.020*
No 1.00 1.00
Stress Rarely 0.40 0.81-1.93 0.249 0.09 0.01-1.30 0.077
Somewhat 1.37 0.33-5.65 0.660 0.37 0.04-1.76 0.339
Much 2.00 0.45-8.96 0.364 0.48 0.16-10.96 0.513
A great deal 1.00 1.00
Perceived health status Bad 0.59 0.27-1.32 0.199 0.88 0.33-1.43 0.879
Neutral 0.69 0.33-1.43 0.310 0.47 0.13-1.76 0.262
Good 1.00 1.00

OR, odd ratio; CI, confidence interval.

1 Unweighted sample size.

2 Weighted sample size.

* p <0.05.

DISCUSSION

This study examined the factors associated with subjective memory problems in cancer survivors. In this study, 7.7% of the cancer survivors indicated frequent memory problems (often or always). Overall, 54.1% experienced memory problems. According to the American Society of Clinical Oncology [14], more than 70% of cancer patients have cognitive problems including attention, thinking, and memory issues. In a study with a nationally representative sample of 9,819 people, 14% of cancer survivors aged over 40 years reported difficulties in remembering. In contrast, up to 8% of those without cancer experience memory difficulties [15]. When comparing cancer survivors and individuals without cancer, the risk of experiencing memory loss is 2.9 times higher in cancer survivors [16]. In Korea, the incidence of objective cognitive decline is 34.1% immediately post-treatment and 22.0% six months after the completion of breast cancer treatment [13]. Moreover, various estimates of cancer-related cognitive disorders have been reported. However, it is difficult to compare our results with those of previous studies because this study targeted all cancer patients and measured only subjective memory problems without controlling for the diagnosis time or chemotherapy.
Having a job decreased “ extreme memory problems” by 0.18 times, while having a lower-than-median individual income increased “ some memory problems” by 2.16 times. Of note, cognitive problems can affect productivity among working cancer survivors [17]. Our results suggest that participants who kept their job had no difficulties with severe memory problems. Furthermore, lower income and poverty have been associated with cognitive impairment [18,19]. Insufficient income can cause psychological stress [20], which ultimately affects cognitive functions [19]. Cancer may need to spend a lot of money during treatment, and thus, may experience stress, which in turn, can affect their cognitive functions. Therefore, it is necessary to develop appropriate support for patients with cancer, including strategies for improving their cognitive functions.
Interestingly, drinking alcohol significantly decreased “ extreme memory problems”. Previous study has reported significant associations between alcohol consumption and mild cognitive impairment [21]. In contrast, a meta-analysis found that light-to-moderate drinking may reduce the risk of cognitive decline in older adults [22]. Based on available evidence, the relationship between alcohol consumption and cognitive decline remains uncertain. In the future, different aspects related to drinking, such as the liquor type, drinking frequency, and duration of alcohol consumption should be considered. The results of this study should be interpreted with care because drinking was classified as present or absent only.
Meanwhile, smoking increased the risk of “ extreme memory problems”. Smoking temporarily improved attention and memory, but decreased cognitive functions in middle-aged adults [23] or those older than 75 years of age [24]. The results of this study support the findings of previous studies and suggest that smoking cessation education is important for maintaining memory among cancer survivors.
Walking three to four days a week significantly lowered the risk of memory problems by 0.15 times compared to not walking. In a meta-analysis, physical activities effectively increased cognitive functions in adults over 50 years of age [25] and demonstrated a significant relationship with lower cognitive function decline in older women [26]. Therefore, moderate-intensity exercise should be considered when developing interventions to improve memory in cancer survivors.
Depression was a significant factor contributing to “ extreme memory problems”. In a previous study by Lee [12], depression was found to be a factor that lowered the cognitive functions of patients with breast cancer undergoing chemotherapy. Additionally, there is a significant association between depression and low cognitive function in cross-country comparative studies [27]. Therefore, depression among cancer survivors should not be overlooked.
The importance of managing cognitive problems in cancer survivors may have been overlooked. There is limited relevant data on memory problems among the adverse side effects related to patients with cancers [15] because memory problems are not directly related to survival. Moreover, cancer survivors may experience periods of ‘ wooly-headedness’ or ‘ being not as sharp’ [28], which is difficult to distinguish from age-related cognitive decline. Therefore, based on the results of this study, it is necessary to carefully observe the cognitive problems of cancer survivors and develop intervention strategies.
This study has some limitations. This study was a secondary data analysis. As such, it was not possible to consider whether chemotherapy was administered or when the cancer diagnosis was made. It is also possible that only relatively healthy cancer survivors eligible to participate in the national data collection were included. Furthermore, as memory problems were subjectively reported only, it was not possible to confirm an objective cognitive decline.

CONCLUSION

This study aimed to identify factors related to memory problems in cancer survivors by using data from the 2019 KNHANES. The results demonstrated that more than half of the cancer survivors reported memory problems. Having a lower-than-median individual income, smoking, and depression were significant potentiating factors, whereas having a job, drinking, and walking three to four days a week reduced the risk of memory problems. Based on the results of this study, it is necessary to develop interventions to improve the cognitive function of cancer survivors.

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