1. Background
Lower urinary tract symptoms (LUTS) refer to a general term encompassing a full spectrum of urinary problems, including urinary retention and voiding, as well as post-micturition symptoms. This condition profoundly affects some aspects of the quality of life of patients, including social and emotional wellness (1) Among various types of LUTS, pollakiuria and nocturnal enuresis have been noted as some of the most exasperating symptoms (2). Pollakiuria is a type of bladder dysfunction, which in toilet-trained children is defined as excessive daytime urination in the absence of polydipsia, diabetes mellitus, nephrogenic diabetes insipidus, daytime polyuria, urinary tract infections (UTI), or viral syndrome. During the daytime, there is a daily voiding frequency of at least once per hour, and the average volume of voided expected bladder capacity (EBC) is usually 15 - 20% (3). It has been suggested that urinary incontinence problems can be associated with lifestyle-related diseases, such as cardiovascular disease, diabetes mellitus, renal dysfunction, lower urinary tract obstruction, and primary sleep disorders (4-6). Therefore, most patients are advised to modify their daily behaviors, such as reducing the consumption of fluids, caffeinated products, and alcohol (7).
A case-control study of non-pregnant women aged ≥ 20 years found an association between urinary incontinence and the consumption of caffeinated, carbonated beverages, citrus fruits, and acidic foods in the period 2007 - 2020 (8). Xie et al.’s study demonstrated that a diet resembling the Mediterranean diet — characterized by a high intake of vegetables, fruits, legumes, and nuts, a moderate intake of fish, and a low intake of dairy products and meat — is linked to reduced urinary urgency and mixed urinary incontinence in women (9). Another population-based study on 2060 women also demonstrated that receiving more calories predicted a higher risk of urinary incontinence and its severity (10). Although urinary incontinence did not correlate with carbohydrate, protein, or fat intake, the saturated/unsaturated fat ratio was positively associated with incontinence. These observations suggest that modifying the diet, as a restrained intervention, can be useful to these patients.
Research evidence is scarce on the relationship between pollakiuria and diet. Moreover, existing data on the relationship between diet and LUTS have been mainly derived from observational studies. Owing to the fact that diet is an easily modifiable element and is often recommended by healthcare professionals as part of a LUTS management program, more high-quality evidence is needed to achieve a better and more comprehensive understanding of the impact of diet on pollakiuria.
2. Objectives
The aim of the present study was to investigate the relationship between the consumption of certain foods, salt, and caffeine and pediatric pollakiuria in comparison with a healthy control group.
3. Methods
3.1. Study Design, Population, and Location
The present research was a matched case-control study conducted on 5- to 7-year-old children referred to a pediatric medical center at Amirkabir Hospital, Arak City, from April 2022 to October 2022. The sample size was calculated using STATA version 11 with the following assumptions: α = 0.05, power = 0.8, P1 = 0.163, and P2 = 0.4 (11). The diagnosis of pollakiuria in children was confirmed by a pediatric nephrologist based on the following definition: A significant urinary frequency of more than eight times a day, distraction that relieves symptoms, disappearance of symptoms during sleep, absence of dysuria or fever, and unremarkable routine urine tests and ultrasound results of the urinary tract (12). Exclusion criteria included the detection of other renal and urinary disorders, as well as urinary tract infections (UTIs). The hospital control group consisted of age- and sex-matched children (frequency matching) referred to the same hospital within the same period. The control group was randomly selected from children with no symptoms of pollakiuria. This study was approved by the Ethics Committee of Arak University of Medical Sciences (IR.ARAKMU.REC.1400.331).
3.2. Data Collection Methods
Written informed consent was obtained from the children’s parents or guardians. A questionnaire was completed for each patient by a trained physician during outpatient visits to collect demographic data (age, sex, and history of urinary incontinence). With light clothing and without shoes, body weight was measured on a scale to the nearest 0.1 kg. Using a measuring tape, height was taken without shoes and recorded to the nearest 0.1 cm. The body mass index (BMI) was calculated by dividing weight (kg) by height squared. Subsequently, the BMI was converted to Z scores using Iranian reference data (13).
A valid and reliable 168-item food frequency questionnaire (FFQ) was then completed by one of the children’s parents with the help of a resident physician. The reliability and validity of the FFQ have been established previously (14). This questionnaire was used to evaluate whether children consumed food items on a daily, weekly, monthly, or yearly basis. Only the consumption of meats, dairy products, vegetables, and caffeinated products was investigated. Parents were asked to specify how often their children consumed each food item over the past year, using the learned serving sizes as a reference. The data were then analyzed by Nutritionist IV software (N Squared Computing, California, USA). Salt intake was determined through an analysis of the FFQ and the average salt consumption of each individual, calculated by dividing the monthly family consumption by the number of family members.
3.3. Data Analysis Methods
Using SPSS software (Version 26; IBM, Chicago), data analysis was performed by applying central tendency and dispersion indices for data presentation. The χ² test was employed to compare categorical data, while the independent t-test was utilized for between-group comparisons of quantitative data with a normal distribution. Using conditional logistic regression, the odds ratio (OR) and 95% confidence intervals (CI) for pollakiuria were calculated regarding the frequency of consumption of meat, dairy products, vegetables, caffeine, and salt.
4. Results
Sixty-four children with pollakiuria and 64 healthy matched controls were enrolled in the study. All variables exhibited a normal distribution. The comparison of gender, age, and BMI did not reveal any significant difference between the case and control groups (Table 1). Table 2 displays the average frequency of consumption of selected food items, including meat, dairy products, vegetables, caffeinated products, and salt, in each group of participants and their association with pollakiuria. Among these food categories, the consumption of only salt (P = 0.003) and caffeine (P < 0.001) was more frequent among children with pollakiuria than their control peers. Regarding the relationship between the consumption of food items and the development of pollakiuria (Table 2), the likelihood of this disorder was significantly associated with the consumption of salt (OR = 1.24; P = 0.002) and caffeine (OR = 1.038; P < 0.001).
Table 1.Baseline Characteristics of the Pollakiuria Group and the Control Group a
| Variables | Pollakiuria Group | Control Group | P-Value b |
|---|---|---|---|
| Age (y) | 6.09 ± 0.88 | 6.16 ± 0.86 | 0.686 |
| Gender | 0.879 | ||
| Male | 33 (51.6) | 30 (46.9) | |
| Female | 31 (48.4) | 34 (53.1) | |
| Height (cm) | 87.52 ± 6.94 | 87.95 ± 7.22 | 0.860 |
| Weight (kg) | 19.05 ± 1.60 | 18.91 ± 1.63 | 0.556 |
| BMI Z-score | 2.27 ± 0.71 | 2.69 ± 0.53 | 0.963 |
Abbreviation: BMI, Body Mass Index.
a Values are expressed as mean ± SD or No. (%).
b P-value by independent t-test or χ2.
Table 2.Odds Ratios and 95% Confidence Intervals for Pollakiuria in Relation to Dietary Intake Habits in Children a
| Variables | Pollakiuria Group | Control Group | P-Value b | OR (95% CI) | P-Value c |
|---|---|---|---|---|---|
| Meats (serving/d) | 1.27 ± 0.31 | 1.19 ± 0.30 | 0.115 | 2.38 (1.46,4.53) | 0.142 |
| Dairy products (serving/d) | 0.48 ± 0.19 | 0.52 ± 0.26 | 0.838 | 0.520 (0.10,1.48) | 0.398 |
| Vegetables (serving/d) | 1.07 ± 0.36 | 0.95 ± 0.42 | 0.067 | 2.28 (1.77,4.35) | 0.074 |
| Caffeine (mg/d) | 45.75 ± 25.42 | 26.61 ± 21.35 | < 0.001 | 1.038 (1.02,1.06) | < 0.001 |
| Salt (g/d) | 5.29 ± 3.71 | 3.40 ± 2.28 | 0.003 | 1.24 (1.00,1.17) | 0.002 |
Abbreviation: OR, odds ratio.
a Values are expressed as mean ± SD or No. (%).
b P-value by independent t-test.
c P-value by logistic regression, adjusted for body weight.
5. Discussion
It is assumed that environmental factors, including diet, are linked with the development of LUTS in children. In this study, we investigated the potential relationship between consuming certain food items and the development of pediatric pollakiuria. Our findings disclosed that the frequent consumption of salt and caffeine could increase the risk of pollakiuria in children. Based on our knowledge, we found scarce articles that examined the relationship between diet and LUTS in children; therefore, the results are mostly compared with existing studies conducted in adults.
In a study by Matsuo et al. on 728 adult patients with LUTS in Japan, it was specified that the excessive consumption of salt on a daily basis adversely affected pollakiuria and nocturnal enuresis (15). In another study on 1545 men aged 30 - 79 years, sodium intake was directly associated with LUTS and the storage symptom score (16). Ozaki et al. reported that daily salt intake (≥ 10 g/day) in Japanese women was independently associated with urine urgency (17). Prolonged consumption of salt, via activating the renin-angiotensin system in the kidney, triggers cellular dehydration and increases osmotic pressure, leading to polyuria. Excessive sodium intake also elevates blood pressure and increases CNS activity (18) which accelerates oxidative stress and bladder hypersensitivity (19). A study by Tsuji et al. showed that a high daily salt intake significantly decreased the effectiveness of 1-desamino-8-D-arginine vasopressin therapy in children with nocturnal enuresis (20). The authors proposed that reducing salt intake should be regarded as a strategy to enhance treatment effectiveness.
In the present study, more caffeine consumption was observed to increase the odds of developing pollakiuria. Consuming caffeine before bedtime has been identified as a significant factor linked to nocturnal enuresis in Ethiopian children aged 5 to 14 years (21). In men with hyperactive bladder, caffeine consumption at a dose of 4.5 mg/kg was reported to be a diuretic, reducing the bladder fullness threshold while increasing the speed of urinary flow (22). A systematic review declared that lower caffeine intake was positively associated with the symptoms of urinary urgency, urinary incontinence, and enuresis, (23)which was attributed to the stimulatory effects of caffeine on the detrusor muscle (24). A randomized clinical trial in children aged 6 - 15 years, comparing a caffeine-restricted group (< 30 mg/day) to a control group (80 - 110 mg/day), showed a significant reduction in bed-wetting frequency after one month in the intervention group (25).
In our study, no association was observed between the risk of pollakiuria and the consumption of dairy products. In line with this notion, Tabara et al., in a cross-sectional study, negated a link between the regular consumption of dairy products and polyuria (26). In another study, Chen et al. reported a positive correlation between the frequency of consuming milk and dairy products and the IPSS (27). Altogether, more studies are needed to verify the relationship between pollakiuria and the intake of dairy products.
We found no relationship between the consumption of vegetables and pollakiuria. It has been shown that the relative risk of LUTS in men is significantly reduced by the daily consumption of fresh vegetables (28). In a prospective cohort study on 785 patients, more frequent consumption of vegetables was reported to be protective against nocturnal enuresis (29). The positive impact of consuming vegetables on urinary problems has also been proven in other studies (11, 30). It seems that the antioxidant phytochemical constituents of vegetables can have preventive or therapeutic effects on diseases associated with LUTS (31). However, this protective effect seems to be dependent on the regular consumption of vegetables. The absence of such a relationship in our study may be attributed to the low vegetable consumption among Iranian children (32). According to Ziaei's study, only 23% of students meet the recommended vegetable intake (≥ 3 times/day), which aligns with our findings (32).
To the best of our knowledge, the present research was the first case-control study investigating the relationship between dietary factors and pediatric pollakiuria. However, our study has some limitations. Our results might have been affected by the small sample size and the errors pertaining to the FFQ. Additionally, due to the lack of comparable studies in children, there may be confounding factors that were not accounted for in our study.
5.1. Conclusions
Based on the findings of the present study, restricting the use of salt and caffeine may be effective in reducing the odds of pollakiuria in children. There is a need to conduct more studies to assess the impact of other dietary factors and adjust for the effects of confounding factors, such as blood pressure, fluid intake, and physical activity.
