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 | |
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.
| 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) | |||
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 | 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) | |||
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.
| 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 | |||||
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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