Cardiovascular risk profiles in divers and non-diving individuals: a Framingham Risk Score analysis

TAYLAN ZAMAN1, NAZİFE INCİLAY TİRSİOGLU2, SAFİYE KUBRA CETİNDAG KARATLI3, MUNİRE KUBRA OZGOK KANGAL1

1Underwater and Hyperbaric Medicine, University of Health Sciences, Gulhane Training and Research Hospital, Ankara, Turkey; 2University of Health Sciences, Gulhane Faculty of Medicine, Ankara, Turkey; 3Family Medicine, University of Health Sciences, Gulhane Training and Research Hospital, Ankara, Turkey.

Summary. Background. Diving involves exposure to hyperbaric conditions and unique physiological stressors that may influence cardiovascular health. However, data comparing cardiovascular risk profiles between divers and non-divers remain limited. Objective. To compare cardiovascular risk profiles between divers and non-diving individuals using the Framingham Risk Score (FRS). Methods. In this retrospective cross-sectional study, 114 male divers and 93 age-matched non-diving males were evaluated. Age, blood pressure, lipid parameters, smoking status, diabetes, hypertension, and body mass index were obtained from medical records. Ten-year cardiovascular risk was assessed using the FRS. Analyses were performed for the overall cohort and according to age groups (≤35 and >35 years). Results. No significant differences were observed between divers and non-divers in overall FRS points or estimated 10-year cardiovascular risk. Among individuals older than 35 years, divers demonstrated significantly lower FRS scores and lower estimated cardiovascular risk percentages than non-divers. Older divers also had lower rates of smoking and hypertension, whereas HDL cholesterol levels were higher. LDL cholesterol levels were higher among divers aged >35 years. Additionally, the proportion of individuals without cardiovascular risk factors was greater among divers. Conclusions. While overall cardiovascular risk profiles were similar between groups, older divers exhibited more favorable cardiovascular risk characteristics than non-divers. These findings may reflect differences in lifestyle characteristics and medical surveillance between divers and non-divers. Prospective studies are warranted to further investigate the relationship between diving and cardiovascular risk.

Key words. Cardiovascular risk, diving/divers, Framingham Risk Score, risk factors, medical surveillance, life style.

Profili di rischio cardiovascolare nei subacquei e nei non subacquei: un’analisi basata sul Framingham Risk Score

Riassunto. Background. L’attività subacquea comporta l’esposizione a condizioni iperbariche e a fattori di stress fisiologico specifici che possono influire sulla salute cardiovascolare. Tuttavia, i dati che mettono a confronto i profili di rischio cardiovascolare tra subacquei e non subacquei rimangono limitati. Obiettivo. Confrontare i profili di rischio cardiovascolare tra subacquei e individui non subacquei utilizzando il Framingham Risk Score (FRS). Metodi. In questo studio retrospettivo trasversale sono stati valutati 114 subacquei di sesso maschile e 93 uomini non subacquei della stessa fascia d’età. Età, pressione arteriosa, parametri lipidici, abitudine al fumo, diabete, ipertensione e indice di massa corporea sono stati ricavati dalle cartelle cliniche. Il rischio cardiovascolare a 10 anni è stato valutato utilizzando l’FRS. Le analisi sono state condotte sull’intera coorte e in base alle fasce d’età (≤35 e >35 anni). Risultati. Non sono state osservate differenze significative tra subacquei e non subacquei nei punteggi complessivi dell’FRS né nel rischio cardiovascolare stimato a 10 anni. Tra gli individui di età superiore ai 35 anni, i subacquei hanno mostrato punteggi FRS significativamente più bassi e percentuali di rischio cardiovascolare stimato inferiori rispetto ai non subacquei. I subacquei più anziani presentavano inoltre tassi più bassi di tabagismo e ipertensione, mentre i livelli di colesterolo HDL erano più elevati. I livelli di colesterolo LDL erano più elevati tra i subacquei di età >35 anni. Inoltre, la percentuale di individui privi di fattori di rischio cardiovascolare era maggiore tra i subacquei. Conclusioni. Sebbene i profili di rischio cardiovascolare complessivi fossero simili tra i due gruppi, i subacquei più anziani presentavano caratteristiche di rischio cardiovascolare più favorevoli rispetto ai non subacquei. Questi risultati potrebbero riflettere differenze nelle caratteristiche dello stile di vita e nella sorveglianza medica tra subacquei e non subacquei. Sono necessari studi prospettici per approfondire la relazione tra immersioni subacquee e rischio cardiovascolare.

Parole chiave. Rischio cardiovascolare, immersioni subacquee/subacquei, Framingham Risk Score, fattori di rischio, sorveglianza medica, stile di vita.

Introduction

Although diving is becoming increasingly popular at both recreational and professional levels, the exposure of individuals to a hyperbaric environment characterized by environmental and physiological stress may have various effects on the cardiovascular system. Cardiovascular diseases (CVDs) are among the leading causes of morbidity and mortality worldwide1,2 and are closely associated with multiple environmental factors such as lifestyle, physical activity, dietary habits, and smoking3-5. Divers are exposed to several factors, including physiological stress induced by high-pressure environments, immersion effects, cold water exposure, and physical exertion, all of which may lead to potential alterations in their cardiovascular risk profiles6,7.

Evaluating cardiovascular risk in divers is of critical importance for enhancing diving safety and preventing sudden cardiac events. The Framingham Risk Score (FRS) is a widely used and reliable tool that estimates the 10-year risk of cardiovascular events by assessing parameters such as age, sex, blood pressure, cholesterol levels, and smoking status8. This scoring system allows for a standardized assessment of cardiovascular risk profiles in both divers and the general population. Whether cardiovascular risk profiles differ between divers and non-divers and which factors may contribute to these differences remains unclear7,8. Professional divers are typically required to undergo periodic medical examinations and maintain fitness standards for diving certification, factors that may influence the cardiovascular risk profile of this population. While the literature suggests that increased physical activity among divers may reduce cardiovascular risk9, other studies have reported that increased smoking rates and prolonged diving exposure may elevate the risk of myocardial infarction and angina pectoris10. These conflicting findings highlight the need for further investigation using standardized cardiovascular risk assessment tools.

In Turkey, the prevalence of major cardiovascular risk factors remains high and has shown an increasing trend in recent years. Hypertension affects approximately one-third of the adult population, with reported prevalence rates ranging from 31.2% to 33.7%11,12. Although awareness and treatment rates have improved over time, blood pressure control remains suboptimal, with control rates reported between 28.7% and 31.7%11,13,14. Obesity, high sodium intake, physical inactivity, and aging are recognized contributors to the growing burden of hypertension14. Furthermore, data from the Turkish Statistical Institute indicate that between 2016 and 2022, the prevalence of diabetes mellitus increased from 10.2% to 11.4%, male obesity prevalence reached 16.8%, and smoking rates increased to 41.3%15. Collectively, these findings highlight the substantial burden of cardiovascular risk factors in the Turkish population, particularly with advancing age.

In the existing literature, studies evaluating cardiovascular risk factors in divers have often been limited by relatively small sample sizes, and data regarding the use of standardized cardiovascular risk assessment tools such as the FRS remain scarce in this population. Comparative analyses between divers and non-divers may help characterize differences in cardiovascular risk profiles and identify factors associated with these differences. Therefore, this study aimed to compare cardiovascular risk profiles between divers and non-divers using the FRS and to examine age-related variations in these profiles.

Materials and methods

Ethics

Our study was deemed ethically appropriate by the Gülhane Scientific Research Ethics Committee with the decision dated 28.06.2024 and numbered 2024-389.

Study Design

This study included male divers over the age of 20 who applied for a medical certificate at the Underwater and Hyperbaric Medicine Clinic of Health Science University (HSU)-Gulhane Training and Research Hospital between 01.01.2017 and 01.01.2024 (diver group), as well as non-diving males aged 20-65 who visited the Family Medicine Outpatient Clinic of HSU-Gülhane Training and Research Hospital for any reason between 01.01.2023 and 01.01.2024 (control group). Because a population-based control group was not available, non-diving individuals attending the Family Medicine Outpatient Clinic were selected as controls. Age and sex matching were applied to improve comparability between groups. The diver group consists of experienced divers who have completed at least 150 dives and are actively working as scuba instructors or commercial divers. This selection criterion was used to ensure inclusion of individuals with substantial diving exposure and to facilitate the assessment of cardiovascular risk profiles within an experienced diving population. Due to the low number of female divers, women were excluded from the study. The control group was selected through a systematic randomization procedure based on the hospital’s medical record system. In this process, male patients aged 20-65 who visited the Family Medicine Outpatient Clinic were assigned unique numbers according to their medical record order. Subsequently, a randomized selection algorithm using a random number generator was employed to determine the control group participants. This method was implemented to minimize selection bias and enhance comparability between groups.

Technical information

Retrospective file reviews were conducted for all included participants to collect the necessary data for calculating the FRS, including age, sex, height, weight, systolic blood pressure, diastolic blood pressure, smoking status, presence of diabetes, presence of hypertension, HDL level, and LDL level. All variables were obtained from routinely collected clinical records available at the time of the medical evaluation. Participants with missing data were excluded from the study.

To assess obesity and high LDL levels, BMI and LDL values were categorized. BMI classifications were defined as normal (18.5-24.9), overweight (25-29.9), and obese (≥30). LDL levels >130 mg/dL were classified as high LDL.

Statistic

Statistical analyses were performed using the Jamovi software (ver. 2.4.8.0). Categorical variables were presented as n (%), while continuous variables were reported as mean ± standard deviation if normally distributed, or as median (min-max) if not normally distributed. Normality of data distribution was assessed using the Shapiro-Wilk test. Descriptive statistics were conducted. Comparisons between the two groups were performed using the Independent Samples t-test if the data were normally distributed with homogeneous variances, Welch’s analysis if the data were normally distributed but with non-homogeneous variances, and the Mann-Whitney U test if the data were not normally distributed. A p-value of less than 0.05 was considered statistically significant.

Results

Study population and general findings

Between 01.01.2017 and 01.01.2024, a total of 153 divers applied to our clinic for routine medical screenings. Among them, 29 individuals were excluded due to being under 20 years old, and 10 individuals were excluded because they were female. Consequently, 114 male divers were included in the study. For the control group, 93 non-diving males aged 20–65 who visited the Family Medicine Outpatient Clinic between 01.01.2023 and 01.01.2024 were selected. The demographic and clinical characteristics of the groups are summarized in table 1.




Overall, no significant difference was observed between divers and the control group in terms of total FRS points and 10-year cardiovascular risk percentage (p=0.091 and p=0.096, respectively).

Cardiovascular risk analysis by age groups

The groups were divided into two subgroups: ≤35 years and >35 years, and analyzed accordingly.

• Total cardiovascular risk: in individuals older than 35 years, median cardiovascular risk percentage and total FRS points differed between groups, with lower values observed among divers than controls (p=0.043 and p=0.025, respectively). However, no significant difference was observed in individuals aged 35 and below (p=0.089 and p=0.090). These findings are presented in table 2, figure 1, and figure 2.










• Smoking status: no significant difference was found in smoking prevalence among individuals aged 35 and below (p=0.065). Among individuals older than 35 years, active smoking was reported in 61.1% (22/36) of controls and 18.0% (9/50) of divers (p<0.005) (table 3).




• Hypertension: there was no significant difference in hypertension prevalence among individuals aged 35 and below (p=0.471). Among individuals older than 35 years, hypertension was present in 19.4% (7/36) of controls and 2.0% (1/50) of divers (p=0.021).

• Blood pressure: systolic blood pressure was significantly higher in the control group compared to divers in both age subgroups (p<0.001 for both). Diastolic blood pressure was significantly lower in the control group among individuals aged 35 and below (p<0.001), but no significant difference was observed in individuals over 35.

• Lipid profile: HDL levels were significantly lower in the control group compared to divers in both the ≤35 and >35 age groups (p<0.001 and p=0.005, respectively). LDL levels showed no significant difference in individuals aged 35 and below (p=0.159). Among individuals older than 35 years, mean LDL levels were higher in divers than in controls (132.6 ± 41.5 vs. 113.8 ± 37.2 mg/dL; p=0.026).

Obesity and lipid profile analysis

Obesity and high LDL prevalence rates are provided in table 4.




The prevalence of obesity was 10.5% (12/114) among divers and 19.4% (18/93) among controls (p=0.064). High LDL levels (>130 mg/dL) were observed in 32.5% and 25.8% of participants, respectively (p=0.287). Although normal BMI was more common among divers (42.1% vs. 33.3%), the difference was not statistically significant (p=0.197). Among participants older than 35 years, LDL >130 mg/dL was present in 48.0% of divers and 30.6% of controls (p=0.099).

Distribution of risk factors

the distribution of cardiovascular risk factors (smoking, hypertension, diabetes, high LDL, and obesity) between divers and the control group was analyzed (table 5).




The proportion of participants without cardiovascular risk factors was greater among divers than controls (33.3% vs. 19.4%, p=0.024). No statistically significant difference was observed in the proportion of participants with three or more risk factors (12.9% vs. 5.3%, p=0.057).

No significant differences were observed between groups with respect to diabetes prevalence, obesity prevalence, or overall Framingham Risk Score in the total cohort.

Discussion

This study compared the cardiovascular risk profiles of divers and non-diving individuals using the FRS and examined age-related differences in these profiles. Overall, no significant difference was found between divers and the control group in terms of total FRS points and 10-year cardiovascular risk percentage (p=0.091 and p=0.096, respectively). However, subgroup analyses showed significantly lower FRS scores and cardiovascular risk percentages among divers older than 35 years (p=0.025 and p=0.043). While both groups maintained an overall low absolute risk (FRS <10%), this age-related difference suggests a possible trend that may warrant closer cardiovascular monitoring in older individuals. Nevertheless, these findings should be interpreted with caution because of the cross-sectional design and the absence of longitudinal follow-up. The observed differences coincided with a higher prevalence of established cardiovascular risk factors, particularly smoking and hypertension, among controls, which is consistent with the general increase in cardiovascular risk with advancing age. Rienks et al. similarly emphasized the importance of cardiovascular risk assessment in older divers, given the age-related increase in cardiovascular risk16. Taken together, these findings suggest that the observed age-related differences may be more closely related to differences in modifiable cardiovascular risk factors than to diving exposure itself.

Several factors may contribute to the more favorable cardiovascular risk profile observed among divers older than 35 years. The prevalence of active smoking was substantially higher in controls than in divers (61.1% vs. 18.0%, p<0.005), and hypertension was more common among controls (19.4% vs. 2.0%, p=0.021), both of which are well-established contributors to cardiovascular risk17. An important alternative explanation for these findings is the healthy worker effect.7 Professional divers are generally required to undergo periodic medical examinations and maintain fitness standards to remain eligible for diving activities. Consequently, divers may represent a healthier subset of the population than clinic-attending controls, suggesting that the observed differences may reflect differences in health behaviors, medical surveillance, and occupational fitness requirements rather than the effects of diving exposure alone. Interestingly, Garbino et al. reported a markedly higher prevalence of hypertension among commercial divers, comparable to that of the general U.S. population18, whereas hypertension was rare in our diver cohort, highlighting potential differences in study populations and occupational settings.

The literature presents conflicting findings regarding the relationship between diving and cardiovascular health. Åsmul et al. reported that extensive diving exposure (more than 150 dives per year or a total of over 2000 air dives) was associated with an increased risk of myocardial infarction and angina pectoris among former professional divers (adjusted RR 2.91, 95% CI 1.23–6.87), suggesting that prolonged exposure to hyperbaric and physiological stressors may adversely affect cardiovascular health10. In contrast, Vulić et al. demonstrated that shallow diving (10-20 m) was associated with enhanced parasympathetic activity, indicating increased vagal tone and potentially favorable cardiovascular adaptations19. Although the present findings are more consistent with the latter observation, the observational design of this study does not allow the relative contributions of diving exposure, occupational fitness requirements, lifestyle characteristics, and other unmeasured factors to be distinguished.

In terms of cumulative cardiovascular risk, the proportion of individuals without any cardiovascular risk factors was significantly higher among divers than controls (33.3% vs. 19.4%, p=0.024), whereas the proportion of participants with three or more risk factors tended to be higher in controls, although this difference did not reach statistical significance (12.9% vs. 5.3%, p=0.057). Similarly, Suresh et al. reported a generally low cardiovascular risk among commercial divers, with no individuals classified as high risk8, while Pougnet et al. found that most professional divers had at least one cardiovascular risk factor7. These findings suggest that although cardiovascular risk factors are common in diving populations, the overall cardiovascular risk profile generally remains low. The relatively high smoking prevalence observed in our control group compared with GATS 2016 data may reflect the hospital-based nature of the control group, while the age-related smoking pattern remained consistent with national survey findings20.

Regarding body composition, obesity was less common among divers than controls (10.5% vs. 19.4%), although the difference was not statistically significant (p=0.064). This finding is consistent with the physically demanding nature of professional diving and with previous reports showing a high prevalence of overweight rather than obesity among divers9. Despite the generally favorable cardiovascular risk profile, divers older than 35 years had significantly higher LDL cholesterol levels than controls (p=0.026). Although oxidative stress has been proposed as a potential contributor to lipid oxidation in divers21, this mechanism was not evaluated in the present study. Moreover, important determinants of lipid metabolism, including dietary habits, alcohol consumption, and physical activity outside diving, were unavailable. Therefore, the observed LDL differences should be interpreted cautiously and warrant further investigation.

Current recommendations from both the South Pacific Underwater Medicine Society and the Spanish Society of Cardiology emphasize regular cardiovascular assessment, particularly in divers older than 45 years, together with appropriate management of modifiable cardiovascular risk factors22,23. Our findings support these recommendations and reinforce the importance of periodic cardiovascular assessment and management of modifiable risk factors in diving populations.

This study has several limitations. The retrospective design may have led to missing data in medical records, and the exclusion of female divers due to their low numbers in the sample may limit the generalizability of the findings. Although the diver group consisted of experienced individuals with at least 150 dives, the lack of detailed data on specific characteristics of the dives, such as depth, duration, frequency, and environmental conditions, limited our ability to evaluate associations between diving exposure characteristics and cardiovascular risk profiles in greater detail. Furthermore, multiple subgroup and secondary analyses were performed; therefore, the possibility of type I error cannot be completely excluded. Moreover, the absence of data on potential confounding factors such as dietary habits, physical activity levels outside diving, alcohol consumption, and socioeconomic status may have influenced the observed associations. Future prospective studies should explore cardiovascular risk profiles in divers using more comprehensive exposure and lifestyle-related data.

Conclusion

In conclusion, older divers in this cohort exhibited lower FRS and a lower prevalence of certain cardiovascular risk factors, particularly smoking and hypertension, compared with non-diving controls. While overall cardiovascular risk profiles were broadly similar between groups, age-related differences were observed among participants older than 35 years. These differences may reflect variations in modifiable cardiovascular risk factors, medical surveillance, occupational fitness requirements, and lifestyle characteristics associated with diving populations. Although the mechanisms underlying these findings remain incompletely understood, they underscore the importance of cardiovascular risk assessment and preventive strategies in both diving and non-diving populations. Further prospective studies are needed to better characterize cardiovascular risk profiles and their determinants among divers.

Conflicts of interest. The authors declare that there is no conflict of interest.

Authors’ contributions. Conceptualization: TZ, MKOK. Data curation: NIT, SKCK. Formal analysis: MKOK. Investigation: TZ, NIT. Methodology: TZ, MKOK Supervision: MKOK, SKCK, TZ. Visualization: TZ Writing – original draft: TZ, MKOK, NIT, SKCK. Writing – review & editing: TZ, MKOK. All authors have reviewed and approved the manuscript’s contents.

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