Association between sun-protective behaviors and hypertension: a cross-sectional study from National Health and Nutrition Examination Survey 2009 to 2014

doi:10.21203/rs.3.rs-2889028/v1

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Association between sun-protective behaviors and hypertension: a cross-sectional study from National Health and Nutrition Examination Survey 2009 to 2014

https://doi.org/10.21203/rs.3.rs-2889028/v1

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published 26 Sep, 2023

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Background

In previous studies, sun-protective behaviors increased cardiovascular incidence. Our present article is to further analyze the potential relationship between sun-protective behaviors (staying in the shade, wearing long-sleeved clothing, and applying sunscreen) and hypertension.

Method

The present cross-sectional study evaluated 8,613 participants (aged 20–60 years) from the National Health and Nutrition Examination Survey (NHANES) obtained between 2009 and 2014. We performed multiple logistic regression analysis to examine the relationship between sun-protective behaviors and hypertension. Subgroup analysis was then performed. Multiple linear regression analysis was utilized to examine the relationship of sun-protective behaviors and each sun-protective behavior with systolic and diastolic blood pressure, stratified by sex and race.

Results

A total of 8,613 participants (weighted n = 127,909,475) were applied in our study, including 1,694 hypertensive subjects. Our study demonstrated that sun-protective behaviors of the 2–3 category were associated with increased risk of hypertension, but not with higher systolic and diastolic blood pressure. In subgroup analysis, men, Mexican American, and 25 < BMI ≤ 30 who reported sun-protective behaviors (2–3) were prone to hypertension. Multiple linear regression models showed that non-Hispanic white men with sun-protective behaviors (2–3) were positively associated with systolic and diastolic blood pressure. The association between other-Hispanic men with frequent wearing long-sleeved clothing and diastolic blood pressure was positively correlated.

Conclusion

Sun-protective behaviors of the 2–3 category could increase the incidence of hypertension, but not increase systolic and diastolic blood pressure. We only found that non-Hispanic white men who reported sun-protective behaviors (2–3) were positively associated with systolic and diastolic blood pressure. These findings suggested that excessive sun-protective behaviors should be avoided.

Hypertension

NHANES

Sun-protective behaviors

Hypertension, defined as measured systolic pressure of ≥ 140 mmHg and diastolic pressure of ≥ 90 mmHg, is a major health problem that traditionally gives rise to atherosclerotic cardiovascular diseases (CVDs) [1]. It commonly coexists with other cardiovascular risk factors and may damage the structures and functions of essential organs, such as the heart, brain, and kidneys, and eventually contribute to their failure [2]. The prevalence and incidence of hypertension vary by country, region, race, and age, and are higher in industrialized countries than in developing countries [3]. Statistical data indicate that in recent three decades, the world has witnessed an increase in hypertension in adults aged 30–79 years from 650 million to 1.28 billion individuals [4]. In 2019, high blood pressure was a major or contributing cause of more than 500,000 deaths in the United States [5]. Hypertension has now become the primary risk factor for cardiac death in the United States [6].

Many studies have found that sunlight provides significant benefits [7]. Sunlight exposure can stimulate vitamin D3 synthesis in the skin,[8] which can promote growth and development in children, as well as decrease the risk of osteoporosis, osteopenia, and fractures in adults [9]. It is well documented that people with the greatest sun exposure have a lower cardiovascular mortality risk in comparison to those with inadequate sun exposure [10] and that increased sun exposure in the summer reduces the incidence of myocardial infarction [11]. However, Excessive sun exposure can increase the threat of melanoma and non-melanoma skin cancers [12] and accelerate skin aging [13]. And as the world population continues to grow, the proportion of indoor workplaces and living increases every year and many people emphasize sun protection [14]. Although this reduces the risk of malignant diseases such as skin cancer, excessive sun protection practices have contributed to the increased risk of cardiovascular disease, metabolic syndrome, multiple sclerosis, and other diseases [14]. For example, one research study has found that people residing in low latitudes and exposed to higher rates of solar radiation had a notably higher incidence of hypertension than those living in high latitudes and exposed to lower rates of solar radiation [15, 16].

Therefore, the present study investigated a potential connection between sun-protective behaviors and hypertension by analyzing adult (aged 20–60 years) patient data from the National Health and Nutrition Examination Survey (NHANES) from 2009–2014.

Data source and study population

Statistical data from the NHANES were analyzed to investigate the relationship between sun-protective behaviors and hypertension. The NHANES is major research study that was carried out by the National Center for Health Statistics, the Centers for Disease Control and Prevention, to assess the state of health and nutrition in the U.S. population. The present study received approval from The National Center for Health Statistics and written informed consent was obtained from all participants. More information is available in the NHANES database, http://www.cdc.gov/Nhanes. A total of 8,613 individuals were included in the study after excluding patients with missing information on sun-protective behaviors, hypertension, and other covariates. The flow chart of the systematic selection process is illustrated in Fig. 1.

Outcome variable

Blood pressure measurements were obtained by professionally trained personnel. Participants with hypertension were informed by their physicians that they conformed to the hypertension criteria. The criteria are systolic blood pressure ≥ 140 mmHg and diastolic blood pressure ≥ 90 mmHg in three blood pressure measurements taken at the same time on a non-same day.

Sun-protective behaviors

Sun-protective behavior was assessed using three variables that included staying in the shade, wearing long-sleeved clothing, and applying sunscreen. These variables were recorded as “always”, “most of the time”, “sometimes”, “rarely”, and “never” in the NHANES. The present analysis categorized the three variables as “rare” (never or rarely), “moderate” (sometimes), or “frequent” (always or most of time). Sun-protective behaviors were then classified as 0, 1, and 2–3 based on the number of behaviors with frequent use in three variables [17].

Covariates

Covariates, including age (20–60 years), sex (men/women), race (non-Hispanic black, non-Hispanic white, Mexican American, other Hispanic and other race), marital status (single/never married, separated/divorced, widowed, married, and others), family poverty income ratio (PIR), body mass index (BMI), educational level (less than high school education/primary education, high school education/secondary education, and college education or above), smoking status, alcohol consumption, serum 25-hydroxyvitamin D [25(OH)D] level (severely deficient: <25 nmol/mL, deficient: 25–49.9 nmol/mL, insufficient: 50–74.9 nmol/mL, and normal values: ≥75 nmol/mL) [18, 19], milk consumption, skin reaction, cardiovascular disease (CVD), diabetes mellitus, hypercholesterolemia, and weak/failing kidney. BMI is the body fat index for the weight (kg) to height (m²) ratio. PIR has been used in several studies as a marker of economic status [20]. Smoking status was categorized as current smoking (smoking every day or having more than 100 cigarettes over the course of their life), former smoking (currently non-smoking and having more than 100 cigarettes in the past), and never smoking (having fewer than 100 cigarettes) [21]. Drinking at least 12 alcoholic beverages of any type in the past year was defined as alcohol consumption [22]. Milk consumption was classified as a regular drinker (> 5 times per week), sometimes drinker (< 5 times per week), or never drinker (never drinking milk). Skin reaction to sun exposure without any protection after no sun exposure for several months was classified as nothing, mild, or severe. Participants with hypercholesterolemia were defined as individuals with high blood cholesterol levels. Participants with diabetes mellitus were diagnosed by a medical professional with hyperglycemia. Participants had a weak failing kidney if a physician diagnosed them with abnormal renal function. Participants with CVD were diagnosed by a physician with angina pectoris, heart attack, congestive heart failure, coronary heart disease, or stroke [23].

Statistical analysis

R (http://www.R-project.org) was used to analyze the dataset. Categorical variables were expressed as percentages (%) and compared using χ tests. Continuous variables were expressed as means ± standard deviation (SD) and compared using dependent-sample t-tests (normal distribution) or Kruskal-Wallis rank sum tests (non-normal distribution).

With sun-protective behaviors (0) as the reference category, multiple logistic regression models were utilized to evaluate the relationship between sun-protective behaviors and hypertension. Subgroup analyses were stratified by sex, race, and BMI. Three models were used in the present analysis: Model 1 (an unadjusted model), Model 2 (adjusted for age, gender, and race), and Model 3 (adjusted for model 2 and educational level, marital status, PIR, BMI, smoking status, alcohol consumption, milk consumption, serum 25-hydroxyvitamin D level, skin reaction, CVD, diabetes mellitus, hypercholesterolemia, and weak/failing kidney). When stratified by a certain variable, the model does not adjust this variable. We used multiple linear regression models to analyze the relationship of sun-protective behaviors and each sun-protective behavior with systolic and diastolic blood pressure, stratified by sex and race. Statistical significance was recognized by the value of P < 0.05.

Description of the study population

The study analysis included data for 8,613 eligible participants (weighted n = 127,909,475), including 4,199 men and 4,414 women. The number of sun-protective behaviors with hypertensive participants was 1,964. The overall means (± SD) of systolic and diastolic blood pressure were 118.53 ± 14.36 and 71.60 ± 11.07. The mean age of study population was 39.01 ± 11.58 years. The percentages of sun-protective behaviors with 0, 1, and 2–3 were 47.7%, 36.8%, and 15.5%. The mean (± SD) of BMI was 28.97 ± 6.87 Kg/m². Race included Mexican American (n = 1,267, 9.3%), other Hispanic (n = 802, 6.1%), non-Hispanic white (n = 3,653, 65.1%), non-Hispanic black (n = 1,760, 11.5%), other race (n = 1,131, 8.0%). The demographic data characteristics organized by sun-protective behaviors status are represented in Table 1.

Association between Sun-protective behaviors and hypertension among different subgroups.

Odds ratio (OR) was used as a measure of risk. Multiple logistic regression analysis was used to determine the association between sun-protective behaviors and hypertension (Table 2). Participants with sun-protective behaviors in the 2–3 category were prone to hypertension (OR = 1.29, 95% CI = 1.00–1.67, P = 0.0496) compared to those without sun-protective behaviors in Model 3. In the subgroup analysis of the fully-adjusted model (Table 2), we found that men, Mexican American, and BMI in the intermediate range who reported sun-protective behaviors (2–3) were prone to hypertension (OR = 1.57, 95% CI = 1.07–2.29, P = 0.0213; OR = 2.26, 95% CI = 1.09–4.74, P = 0.0294; OR = 1.78, 95% CI = 1.15–2.76, P = 0.0098).

Association between sun-protective behaviors with SBP and DBP.

We also assessed the association of sun-protective behaviors with systolic and diastolic blood pressure using multiple linear regression analysis (Table 3). We found that sun-protective behaviors had no significant difference with systolic and diastolic blood pressure. The non-Hispanic white men who reported sun-protective behaviors (2–3) had positive association with systolic and diastolic blood pressure in the fully-adjusted model (95% CI = 1.30–7.40, P = 0.0052; 95% CI = 0.08–5.08, P = 0.0433).

Association between each sun-protective behavior with SBP and DBP.

Additional multiple linear regression analysis was used to assess the association of each sun-protective behavior with systolic and diastolic blood pressure (see Additional file 1). In the fully-adjusted model, we found that the association between other-Hispanic men with frequent wearing long-sleeved clothing and diastolic blood pressure was positively correlated (95% CI=-0.69–10.34, P = 0.0253).

This is an article from a cross-sectional study using NHANEA analysis that confirmed a positive association between sun-protective behaviors and hypertension. Opländer study confirmed that ultraviolet A (UVA) radiation was associated with lower blood pressure [24]. Feelisch indicated that the drop in blood pressure was due to arterial vasodilatation caused by ultraviolet A (UVA) radiation and found that the skin can mobilize nitric oxide through photolysis of cutaneous nitrite or nitrate to lower blood pressure with ultraviolet A (UVA) radiation [25]. Meanwhile, an animal study indicated that the mechanism of rat vascular smooth muscle photorelaxation was mediated by NO from the ultraviolet A (UVA) radiation [26]. The result also was observed in our study.

In the sex stratified analysis, the results confirmed a greater risk of hypertension in men than in women. And among the different races, only Mexican American with sun-protective behaviors (2–3) showed a positive correlation with hypertension in model 3. The analysis of people with different BMI suggests that those in the intermediate range are at greater risk of developing hypertension. There are no studies to explain these results. For these results, it is possible that the sample size of the data we analyzed was not large enough to cause this.

To acknowledge the relationship of sun-protective behaviors with systolic and diastolic blood pressure stratified by sex and race, we performed a multiple linear regression and found no significant differences. we found significant differences between non-Hispanic white men who reported sun-protective behaviors (2–3) with diastolic and systolic blood pressure. Meanwhile, an analysis with data from patients with kidney failure in the US indicated that lowering blood pressure was associated with ultraviolet A (UVA) radiation. Ultraviolet intensity was negatively correlated with systolic blood pressure and not significantly correlated with diastolic blood pressure [27]. There are differences from our study, which we think may be the following, first, the study was selected from patients with renal failure, while most of our study was normal population. Second, the study was precise to regional ultraviolet A (UVA) radiation intensity, whereas in our study we relied mainly on questionnaire form. Third, we adjusted for different covariates.

In our study, analysis of each sun-protective behavior and hypertension combination is shown in Additional file 1. After adjusting for confounders, the outcomes showed that the association between other race men who reported wearing long-sleeved clothing frequently and diastolic blood pressure was positively correlated. Staying in the shade and applying sunscreen were not associated with increased risk of hypertension. There are no relevant studies examining the relationship between each sun-protective behavior and hypertension, and more study is needed to verify the results.

Hypertension causes a great number of CVD morbidity and mortality cases [28]. Decreasing blood pressure levels has a significant influence on reducing the societal disease burden [29]. The present study adjusted for several potential confounders in the NHANES to analyze the association between sun-protective behaviors and hypertension, confirming that individuals with sun-protective behaviors are more likely to have hypertension. In the future, patients will be able to improve their blood pressure by following appropriate sun-protective behavior recommendations provided by their medical practitioners.

There were several limitations in the present study. First, the cross-sectional nature of the study introduced intrinsic limitations. The data from the NHANES were obtained between 2009 and 2014. In the future, a randomized controlled study will be necessary to verify these results. Second, the history of hypertension and sun-protective behaviors were self-reported, resulting in under- or over-reported questionnaire outcomes. Finally, the participants were 20–60-years-old. Given that hypertension often occurs in the elderly, future research will need to focus on patients older than 60 years.

The present cross-sectional study results demonstrated that sun-protective behaviors of the 2–3 category were associated with increased risk of hypertension, but not with higher systolic and diastolic blood pressure. We only found that non-Hispanic white men who reported sun-protective behaviors (2–3) were positively associated with systolic and diastolic pressure. Consequently, patients should be encouraged to avoid excessive sun protection due to the high risk of hypertension. Further randomized controlled studies should focus on confirming the association between sun-protective behaviors and hypertension.

NHANES: National Health and Nutritional Examination Survey; CVDs: cardiovascular diseases; CVD: cardiovascular disease; PIR: family poverty income ratio; BMI: body mass index; 25(OH)D: serum 25-hydroxyvitamin D; UVA: ultraviolet A; SBP, systolic blood pressure; DBP, diastolic blood pressure.

Acknowledgements

We are grateful to the NHANES authors for providing the dataset for analysis in this study. We also thank International Science Editing (http://www.internationalscienceediting.com) for editing this manuscript.

Authors' contributions

SPY and FD participated in the initial plan, design of the study, data interpretation, and manuscript drafting. ZKW and RSL performed the statistical analysis and participated in data interpretation and manuscript revision. XZX, CL, XCH, YL, and CFW participated in data interpretation and manuscript drafting. DYL, LL, and TDX critically reviewed, edited, and approved the manuscript. All authors read and approved the final manuscript.

Funding

This study was supported by the Jiangsu Provincial Health Commission Project Fund (Grant number: M2020015), Jiangsu Provincial Science and Technology Department Social Development Fund (Grant number: BE2019639), Jiangsu Traditional Chinese Medicine Science and Technology Development Plan Project (Grant number: YB201988) and Xuzhou innovative plan to promote science technology (Grant number: KC21192).

Availability of data and materials

The dataset supporting the conclusions of this article is available in the NHANES repository, https://www.cdc.gov/nchs/nhanes.

Ethics approval and consent to participate

The present study received approval from The National Center for Health Statistics and written informed consent was obtained from all participants.

Consent for publication

Not applicable.

Competing interests

The authors declare no potential conflict of interests.

Authors’ information

¹Department of General Practice, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221000, People’s Republic of China. ²Department of Cardiology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221000, People’s Republic of China. ³Department of Stomatology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221000, People’s Republic of China. ⁴Department of Nuclear Medicine, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221000, People’s Republic of China. ⁵Institute of Cardiovascular Disease Research, Xuzhou Medical University, Xuzhou, Jiangsu, 221000, People’s Republic of China

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Tables are available in Supplementary Files section.

No competing interests reported.

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You are reading this latest preprint version

Association between sun-protective behaviors and hypertension: a cross-sectional study from National Health and Nutrition Examination Survey 2009 to 2014

Status:

Journal Publication

Version 1

Abstract

Background

Method

Results

Conclusion

Figures

Background

Methods

Data source and study population

Outcome variable

Sun-protective behaviors

Covariates

Statistical analysis

Results

Description of the study population

Discussion

Conclusion

Abbreviations

Declarations

References

Tables

Additional Declarations

Supplementary Files

Status:

Journal Publication

Version 1