Abstract
This cohort study analyzes the prevalence of overweight and obesity among preschool children in Sweden before, during, and after the COVID-19 pandemic and longitudinal trends in body mass index.
Excessive childhood weight gain has been associated with the COVID-19 pandemic globally, attributed to its negative effects on diet and physical activity caused by social restrictions and reduced access to preschools.1 Children from low socioeconomic backgrounds and with preexisting overweight were particularly affected. Childhood obesity increases the risk of obesity in adulthood, with greater risk of cardiovascular diseases, cancer, and lower quality of life.2
Sweden reported increased childhood overweight and obesity during the COVID-19 pandemic despite absence of a formal lockdown.3 In Sweden, regular visits to child health services are free for children aged 0 to 6 years. The visits include growth measurements. Growth data are, in some regions, automatically transferred to the Swedish Child Health Services Register (BHVQ), with high data coverage.4
Few studies have examined how increased prevalence of childhood overweight and obesity changed after COVID-19. We analyzed longitudinal trends in body mass index (BMI) (weight in kilograms divided by height in meters squared) and frequency of overweight and obesity in Swedish preschool children before, during, and after the pandemic.
Methods
This retrospective, population-based cross-sectional study included longitudinal follow-up of children in Sweden for whom multiple growth measures were available. The Swedish Ethical Review Authority approved the study; we followed the STROBE reporting guideline. Caregivers of children approved their registration in BHVQ.
Anthropometric data, sex, and date of birth were obtained from BHVQ. Data were collected for regions Dalarna, Jönköping, and Sörmland from May 2015 to May 2023. Data on race and ethnicity were not registered.
The original dataset contained 51 717 children (Table 1). Growth data within the age ranges of 3 (853-1186 days), 4 (1401-1551 days), and 5 (1766-2100 days) years were included, and incorrect data (n = 31) were deleted. The final study included 50 833 children, categorized by sex-specific BMI-for-age in months. Weight categories, as defined by International Obesity Task Force, were underweight (BMI <17), normal weight (17-25), overweight (26-29), and obesity (≥30).5 Time periods were before COVID-19 (before May 1, 2020), early COVID-19 (May 1, 2020, to May 31, 2021), late COVID-19 (June 1, 2021, to April 1, 2022), and after COVID-19 (after April 1, 2022).
Table 1. Participating Children Aged 3, 4, and 5 Years During Different Periods of the COVID-19 Pandemica.
| COVID-19 period by age | Sex, No. (%) | Total, No. (%) | |
|---|---|---|---|
| Girls | Boys | ||
| 3 y | |||
| Before | 7773 (49.1) | 8051 (50.9) | 15 824 |
| Early | 4479 (48.5) | 4757 (51.5) | 9236 |
| Late | 3706 (48.9) | 3865 (51.1) | 7571 |
| After | 7013 (48.9) | 7322 (51.1) | 14 335 |
| Total | 22 971 (48.9) | 23 995 (51.1) | 46 966 |
| 4 y | |||
| Before | 4941 (49.5) | 5041 (50.5) | 9982 |
| Early | 3259 (49.5) | 3325 (50.5) | 6584 |
| Late | 3104 (48.9) | 3245 (51.1) | 6349 |
| After | 4718 (48.6) | 4988 (51.4) | 9706 |
| Total | 16 022 (49.1) | 16 599 (50.9) | 32 621 |
| 5 y | |||
| Before | 3055 (49.7) | 3086 (50.3) | 6141 |
| Early | 2680 (48.9) | 2802 (51.1) | 5482 |
| Late | 2362 (49.5) | 2405 (50.5) | 4767 |
| After | 4637 (48.6) | 4898 (51.4) | 9535 |
| Total | 12 734 (49.1) | 13 191 (50.9) | 25 925 |
Based on the length of the periods, children may have had multiple growth measurements in the period before the COVID-19 pandemic but not in the other periods. Because some children were measured once, twice, or several times, estimation of a mean or median age for the entire cohort was not possible.
Frequencies and percentages were used for descriptive purposes, and χ2 tests for comparisons. Statistical significance was set at P < .001.
Results
Among the 50 833 children, 25 976 (51.1%) were males and 24 857 (48.9%) were females. In 3-year-old children, prevalence of normal weight was lowest during early COVID-19 (82.1%) (Table 2). Overweight (13.2%) and obesity (3.4%) had the highest prevalence during early COVID-19 and returned to before–COVID-19 levels in the late– and after–COVID-19 periods. Four-year-old children had a similar pattern. For 5-year-old children, prevalence of overweight and obesity did not change significantly. In longitudinal analysis, incidence of increasing BMI decreased from early COVID-19 to after COVID-19 for all age groups.
Table 2. Proportions of Participants According to BMI Classifications During the Different Periods Related to the COVID-19 Pandemic.
| COVID-19 period by age | BMI classification, No. (%)a | Total, No. | Longitudinal analysis of BMI classification, No. (%) | Total, No. | |||||
|---|---|---|---|---|---|---|---|---|---|
| Underweight | Normal weight | Overweight | Obesity | Decreased | Stable | Increased | |||
| 3 y b | |||||||||
| Before | 251 (1.6)c | 13 364 (84.5)c | 1836 (11.6)c | 373 (2.4)c | 15 824 | NA | NA | NA | NA |
| Early | 121 (1.3)c | 7585 (82.1)c | 1215 (13.2)c | 315 (3.4)c | 9236 | NA | NA | NA | NA |
| Late | 161 (2.1)c | 6378 (84.2)c | 854 (11.3)c | 178 (2.3)c | 7571 | NA | NA | NA | NA |
| After | 235 (1.4)c | 12 059 (84.1)c | 1708 (11.9)c | 1199 (2.6)c | 14 335 | NA | NA | NA | NA |
| Tests of column proportions | L > B, E, A | B, L, A > E | E > B, A, L | E > B, A, L | NA | NA | NA | NA | NA |
| 4 y | |||||||||
| Before | 190 (1.9)c | 8501 (85.2)c | 1032 (10.3)c | 259 (2.6)c | 9982 | 530 (6.0)c | 7864 (88.5)c | 493 (5.5)c | 8887 |
| Early | 93 (1.4)c | 5473 (83.1)c | 772 (11.7)c | 246 (3.7)c | 6584 | 374 (6.3)c | 5131 (86.6)c | 423 (7.1)c | 5928 |
| Late | 119 (1.9)c | 5408 (85.2)c | 628 (9.9)c | 194 (3.1)c | 6349 | 519 (8.9)c | 5028 (86.7)c | 254 (4.4)c | 5801 |
| After | 210 (2.2)c | 8292 (84.8)c | 959 (9.9)c | 245 (2.5)c | 9706 | 622 (6.6)c | 8280 (88.5)c | 459 (4.9)c | 9361 |
| Tests of column proportions | B, L, A > E | B, L, A > E | B, E > L, A | E > L > A | NA | L > B, E, A | B, A > E, L | E > B > L | NA |
| E > B | E > A | ||||||||
| 5 y | |||||||||
| Before | 116 (1.9) | 5077 (84.4) | 688 (11.2) | 260 (4.2) | 6141 | 251 (4.7)c | 4659 (87.7)c | 400 (7.5)c | 5310 |
| Early | 95 (1.7) | 4528 (84.4) | 612 (11.2) | 247 (4.5) | 5482 | 171 (3.5)c | 4295 (88.4) | 391 (8.1)c | 4857 |
| Late | 100 (2.1) | 3938 (83.9) | 517 (10.8) | 212 (4.4) | 4767 | 245 (5.6)c | 3881 (88.9) | 242 (5.5)c | 4368 |
| After | 202 (2.1) | 7990 (85.8) | 982 (10.3) | 361 (3.8) | 9535 | 421 (4.9)c | 7656 (89.4)c | 488 (5.7)c | 8565 |
| Tests of column proportions | NA | NA | NA | NA | NA | B, L, A > E | A > B | B, E > L, A | NA |
Abbreviations: A, after COVID-19; B, before COVID-19, BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); E, early COVID-19; L, late COVID-19; NA, not applicable.
Classifications were defined as underweight (BMI <17), normal weight (BMI 17-25), overweight (BMI 26-29), and obesity (≥30).
Before 3 years of age, BMI changes rapidly, and there is less evidence regarding the validity of BMI as a marker of overweight and obesity between 2 and 3 years of age. Hence, longitudinal changes in BMI for children aged 3 years were not analyzed.
Significant difference (P < .001) in proportions between periods.
Discussion
To our knowledge, this is the first study exploring preschool children’s BMI changes before, during, and after the COVID-19 pandemic. In our cohort, increased rates of overweight and obesity during early COVID-19 decreased to prepandemic levels afterward in 3- and 4-year-old children, whereas prevalences of both were relatively stable for 5-year-old children. Longitudinal analyses confirmed that a significant proportion of children had a lower BMI class after the pandemic.
Although there were no formal lockdowns in Sweden, many children were absent from preschool3 and without nutritious food and regular outdoor activities. This may explain the trends seen in 3- and 4-year-old children.
This study was limited in that analyzed data contained only 3 regions. However, prevalence of overweight for 4-year-old children was consistent with nationwide Swedish surveys, indicating generalizability of our findings at the national level.6 These results might be specific to Sweden, and future studies in other populations are important.
Return of earlier gained overweight and obesity to prepandemic levels after COVID-19 further indicates that the weight gains observed were associated with the pandemic. In addition, negative consequences of an unhealthy weight status could be reversible for the youngest age group.
Data Sharing Statement
References
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Associated Data
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Supplementary Materials
Data Sharing Statement
