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Abstract

Aim

Limited cardiovascular disease (CVD) risk data are available for firefighters worldwide. This comparative study was aimed at investigating the biochemical and nutritional indices of firefighters in Iran.

Materials and methods

Individuals’ anthropometric measurements, including weight, height, and waist and hip circumferences, were measured and the percent of body fat (BF%) was also obtained. Blood sampling was done in order to determine lipid profile, including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), lipoprotein a (Lp(a)) and fasting blood sugar (FBS) concentrations. Systolic and diastolic blood pressures (SBP and DBP) were also measured.

Results

The mean ages of firefighters and administrative staff were 42.45 ± 6.75 and 44.64 ± 5.83 y, respectively. The prevalence of overweight and obesity was 45% and 24% in firefighters and 54% and 23% in administrative staff, respectively. High waist-to-hip and waist-to-stature ratios were detected in 26.4% and 81.3% of firefighters versus 33.3% and 89.7% of the control group, respectively. No significant differences were observed between the mean of TC, TG, HDL-C, LDL-C and FBS concentrations. The mean of Lp(a) was significantly higher among firefighters (P<0.05). About half of the subjects in both groups had TC >5.17, TG >1.69, HDL-C <1.03 nmol/L and Lp(a) >25 mg/dL. There were no significant differences between the SBP and DBP of subjects. There was no significant difference in smoking habits between the two groups.

Conclusions

Considering the high prevalence of overweight and obesity, high TC, TG and Lp(a) and low HDL-C concentrations among all firefighters, it seems necessary to provide fitness-promotion and nutritional education programs for the prevention of obesity-related chronic diseases such as CVD.

Introduction

Firefighting is known to be a strenuous occupation. Cardiovascular disease (CVD) is the major reason for on-duty deaths among firefighters.¹ One of the biggest killers of firefighters every year is not job-related factors such as building collapse, entrapment or fire impingement.² Forty-five percent of firefighter-related deaths are because of heart attacks.³ According to a study conducted by the National Fire Protection Association in the USA, a large number of firefighters who died from heart attacks and strokes had serious pre-existing conditions, such as hypertension and arteriosclerosis, that contributed to the heart attack.⁴

Non-modifiable cardiovascular risk factors include age, gender and familial disease history and modifiable cardiovascular risk factors include diabetes mellitus, high total cholesterol (TC), high triglycerides (TG), high blood pressures, overweight and obesity.⁵ With multiple CVD risk factors, individuals face an increased risk for morbidity and all-cause mortality.⁶

Glueck et al. ⁷ found that male firefighters with CVD had statistically significant increases in systolic and diastolic blood pressures (SBP and DBP), low-density lipoprotein cholestorol (LDL-C), TC and TG levels in comparison with those without CVD. Soteriades et al. ⁸ found statistically significant increases in obesity and TG in a sample of on-duty firefighters during a four-year follow-up period. They also examined the distribution of body mass index (BMI) and its association with major CVD risk factors in Massachusetts firefighters and found that the mean BMI and the prevalence of obesity increased among 332 firefighters at the follow-up examination. More recently, Soteriades et al. ⁹ found that every one-unit increase in BMI was associated with a 5% increased risk of job disability. Results of this study have demonstrated that obesity in US firefighters is associated with lower work performance, higher work limitations, higher workers’ compensation claims, disability retirement and disability pension, and mortality.

Obesity, despite being a significant determinant of fitness for duty, is reaching epidemic levels in the workplace. Firefighters’ fitness is important to their health and to public safety. Obesity is a major concern among firefighters and shows worsening trends over time.¹⁰ As an independent CVD risk factor, obesity predisposes individuals to coronary heart disease (CHD), increases the risk of mortality from CHD, and increases the burden of other cardiovascular risk factors.¹¹ In terms of increasing the burden of other cardiovascular risk factors, obesity is associated with lower HDL-C and higher TC, TG, LDL-C concentrations,¹² fasting blood sugar (FBS)¹³ and higher blood pressure levels.¹⁴

Smoking as one of the well-recognized CVD risk factors may be associated with a risk of death from CHD in firefighters. Tobacco smoking as a form of stress reduction is an important social and health problem in this group.¹⁵

This study has been carried out to compare lipid profile, serum glucose and prevalence of obesity among firefighters with those of administrative staff in the fire department and find more practical recommendations for controlling obesity and other CVD risk factors.

Methods

Subjects

A sample of 91 male professional firefighters and 39 male administrative staff of fire stations were selected for evaluating biochemical and anthropometric indices. The firefighters were randomly chosen from all 325 firefighters located in eight fire stations in the city of Ahvaz. Ahvaz is one of the five largest cities of Iran, which is located by the Persian Gulf. All 39 male staff members working in administrative positions in the central fire station were recruited as a control group. All subjects aged more than 25 years old and with an employment history above two years were included in this study. All individuals gave their written consent and were assured that their data would be confidential.

Measurements

Data collection was carried out during autumn 2007. Collected variables were anthropometric indices, including weight, height, and waist and hip circumferences. A blood sample was taken after a 12 h fast to determine lipid profile, including TC, TG, LDL-C, HDL-C, Lp(a) and FBS concentrations. These blood tests were carried out by a reference laboratory. SBP and DBP levels were measured in the seated position. Subjects’ weights and heights were measured using the SECA ARTISTA 830 scale (Germany) and a non-stretchable wall meter, respectively. Individual BMIs were calculated as weight (kg) divided by squared height (m²) and subjects’ BF% values were measured using the bioelectrical impedance analysis method by an OMRON BF-302 (Japan) with standard errors of estimate of 4.1%. Obesity was defined as waist-to-hip ratio (WHR) above 0.9,³ waist-to-stature ratio (WSR) above 0.5⁴ and BF% above 24%¹⁶ for males. The physical activity level was measured using the Baecke questionnaire, in which Baecke et al. developed a questionnaire for evaluating a person's physical activity and categorizing it into three indices: work, sport and leisure activities.

Statistics

By principal components analysis, three conceptually meaningful factors were distinguished. They were interpreted as: (1) physical activity at work; (2) sport; (3) physical activity during leisure time excluding sport.¹⁷ Smoking status was obtained through a personal questionnaire. We defined cases reported to have smoking as a risk factor as current smokers, unless they had quit smoking for more than 12 months.¹⁸

Data were analysed by independent-t, Chi-square and Mann–Whitney U tests, using SPSS software version 11.5. P values less than 0.05 were regarded as significant.

Medical ethics

All subjects gave their written consent and no names were disclosed. The study protocol was approved by the University Medical Ethics Committee.

Results

The mean ages of firefighters and administrative staff were 42.45 ± 6.75 and 44.64 ± 5.83 y, respectively. More than 51% of administrative staff and 39.6% of firefighters were above 45 years. There was no significant difference between the ages of both groups (P = 0.080). Most of the participants were married (100% of administrative staff and 95.6% of firefighters) and most of them were ≤ high school diploma (51.3% versus 64.8%) in both groups, which represents the similarity of the groups (Table 1).

Table 1

Basic characteristics of the groups

		Firefighters N = 91	Administrative staff N = 39
Variable		Mean ± SD	Mean ± SD	P*
Anthropometric indices and blood pressures	Age (Y)	42.45 ± 6.75	44.64± 5.83	0.080
	Weight (kg)	81.4 ± 13.7	80.1 ± 12.5	0.612
	Height (cm)	173.5 ± 5.9	171.5 ± 5.6	0.071
	Waist circumference (cm)	97.3 ± 11.3	97.3 ± 11.4	0.972
	Hip circumference (cm)	106.4 ± 7.9	105.2 ± 7.2	0.419
	BMI (kg/m²)	27.0 ± 4.2	27.2 ± 3.9	0.817
	WHR	0.91 ± 0.06	0.92 ± 0.06	0.596
	WSR	0.56 ± 0.06	0.56 ± 0.06	0.657
	BF (%)	22.07 ± 6.00	23.74 ± 10.07	0.244
	SBP (mmHg)	120 ± 17	123 ± 16	0.261
	DBP (mmHg)	83 ± 13	86 ± 11	0.278
Physical activity indices	Work index	4.23 ± 2.20	3.30 ± 1.79	0.025
	Sport index	2.32 ± 0.72	2.02 ± 0.67	0.031
	Leisure index	2.58 ± 0.74	2.45 ± 0.62	0.383
Smoking statues	Years of smoking	20.09 ± 9.48	17.37 ± 9.97	0.488
	Cigarettes smoked per day	18.4 ± 13.4	15.8 ± 7.6	0.592

*P value for t-test

BMI, body mass index; WHR, waist-to-hip ratio; WSR, waist-to-stature ratio; BF, body fat; SBP, systolic blood pressure; DBP, diastolic blood pressure

Table 1 also shows the anthropometric criteria, physical activity indices, blood pressures and smoking status. No significant difference was seen in the mean of all anthropometric criteria between the two groups. The mean of BMI in both groups was in the range of overweight. The mean WHR and WSR were more than the normal values in both groups.

There were significant differences between mean work and sport indices of both groups. Firefighters had high physical activity levels rather than the other group, according to their high work and sport indices.

Table 2 represents the categories of BMI and BF%. The prevalences of overweight and obesity were 69.3% in firefighters and 76.9% in administrative staff based on BMI categories.¹⁹ The prevalences of overfatness and obesity were 46.2% and 53.8% in firefighters and the control group, respectively, based on BF%¹⁶. The prevalences of abdominal obesity were 64% and 81% in firefighters and 56% and 90% in the other group, respectively, based on WHR and WSR.

Table 2

Anthropometric categorization, based on BMI and BF%

BMI (kg/m²)			BF (%)
	Administrative staff	Firefighters		Administrative staff	Firefighters
Thin (<18.5)	2.6	3.3	Thin (<8)	5.1	1.1
Normal (18.5–24.9)	20.5	27.5	Normal (8–23.9)	41	52.7
Overweight (25–29.9)	53.8	45.1	Overfat/obese (≥24)	53.8	46.2
Obese (≥30)	23.1	24.2	Overfat/obese (≥24)	53.8	46.2

BMI and BF% classifications are according to NIH,¹⁹ 1998 and Gallagher, 2000¹⁶

Figures denote percent of subjects in each category

Table 3 shows the mean of biochemical indices. No significant differences were observed between the mean of biochemical indices except for Lp(a), which was significantly high among firefighters (P < 0.05). The mean TG and Lp(a) levels were above normal values in both groups. The percentages of subjects in both study groups with high fasting blood lipid and glucose levels are shown in Table 4. About half of the firefighters and administrative staff had high TC, TG and Lp(a) and low HDL-C concentrations.

Table 3

Mean of biochemical indices of both groups

	Firefighters N = 91	Administrative staff N = 38
Biochemical indices	Mean ± SD	Mean ± SD	P*
TC	5.0 ± 1.2	5.0 ± 0.8	0.966
TG	1.8 ± 1.0	2.0 ± 1.1	0.295
HDL-C	1.1 ± 0.2	1.1 ± 0.2	0.867
LDL-C	3.1 ± 0.9	3.0 ± 0.7	0.879
Lp (a)	38/56 ± 34/95	27/51 ± 23/83	0/024
FBS	4/7 ± 0.8	4.7 ± 1.3	0.125

All values in mmol/L except Lp(a) values, which are in mg/dL

TC, total cholesterol; TG, triglycerides; HDL-C, high density lipoprotein cholesterol; LDL-C, low density lipoprotein cholesterol; Lp (a), lipoprotein a; FBS, fasting blood sugar

Table 4

Subjects at risk of CVD according to the blood lipid profile and glucose concentrations in both groups*

	Firefighters N = 91		Administrative staff N = 38
Biochemical indices	Percent	Frequency	Percent	Frequency	P*
TC >5.17 mmol/L	42.9	39	41	16	0.548
TG >1.69 mmol/L	47.3	43	53.8	21	0.262
HDL-C <1.03 mmol/L	44	40	43.6	17	0.544
LDL-C >3.36 mmol/L	33	30	23.1	9	0.203
FBS >6.11 mmol/L	12.1	11	15.4	6	0.379
LP (a) >25 mg/dL	52.7	48	41	16	0.182

*Based on reference [19]

TC, total cholesterol; TG, triglycerides; HDL-C, high density lipoprotein cholesterol; LDL-C, low density lipoprotein cholesterol; Lp (a), lipoprotein a; FBS, fasting blood sugar

The mean of SBP and DBP of both groups are shown in Table 1. There were no significant differences between the mean of SBP and DBP levels in both groups. However, 21% of administrative staff and 14% of firefighters had high blood pressures (above 140/90 mmHg).

Nearly 30% of firefighters and 21% of administrative staff were active smokers. The mean years of smoking and the mean cigarettes used per day in both groups, as shown in Table 1, were not significantly different between the two groups.

Discussion

Comparing the prevalence of overweight and obesity between the two groups, both groups tended to be obese and overweight as measured by BMI, BF%, WSR and WHR. A BMI value does not distinguish between an individual's muscle mass and fat mass, so we measured BF% to determine an individual's fat mass. Considering all anthropometric indices, Ho et al. ²⁰ has shown that WSR is the best anthropometric index that consistently predicts cardiovascular risk factors and health conditions compared to WHR and waist circumferences. Most of the subjects had WSR higher than 0.5 as a CVD predictor.

However, a majority of the subjects had an increased risk of CVD because of their high levels of BMI, WHR and WSR and the high prevalence of overweight and obesity. This result is a cause of concern because mortality from CHD increases with increased BMI values.⁶ In addition, both groups had an elevated prevalence of high TG, TC and Lp(a) concentrations on the one hand, and low HDL-C concentrations on the other hand, which are associated with an increased risk for CHD.

It was also found that because of the heavy workload among firefighters, their work index was higher than administrative personnel. On the other hand, the fire department has created scheduled exercise programs for this strenuous job, which is compulsory for firefighters; hence the sport index was significantly higher among firefighters. It had been postulated that firefighters are more active and have high physical activity levels. While it is worthy that the fire department requires exercise for firefighters, their results strongly suggest that the program is insufficient (given the excess adiposity we observed by various measures) and their outcomes are not much better than administrative staff. On the other hand, the sedentary lifestyle among administrative staff has made this group overweight and obese. This finding was witnessed in similar sedentary posts, where more than 75% of official personnel were obese or overweight in Iran.²¹

By comparing the percent of firefighters with obesity in Iran versus the USA, it seems that the proportion of obese subjects and the average BMI are similar to those in US firefighter studies.²²

Outcomes from studies by Clark et al. ²³ and Kales et al. ²² were similar to ours, in which nearly 80.7% of firefighters were found to be overweight, obese or morbidly obese in Clark's study and 87% of firefighters were overweight and 34% were obese in Kales's study.

In the study of Byczek et al.,⁶ in which the prevalence of obesity was high among firefighters, elevated BMI values had positive significant associations with other CVD risk factors such as elevated blood pressure, TG and FBS concentrations and a negative significant association with lower HDL-C levels.

During a mean follow-up of 8.4 years, Nagaya et al. ²⁴ demonstrated that policemen/firefighters had significantly increased risk (approximately 60%) for incident diabetes mellitus. The increased risk was due to a larger BMI in policemen/firefighters.

To help reduce the overall risk for CHD, weight reduction is recommended as an initial means to increase HDL-C levels and to decrease TG, LDL-C and TC concentrations, blood pressures and high FBS levels.⁶

Considering the high prevalence of overweight and obesity among both operational and administrative staff, it seems necessary to provide fitness-promotion and nutritional education programs to prevent obesity-related chronic diseases such as CVD. Moreover, the findings of this study suggest that administrative staff need tailored exercise programs to change their sedentary lifestyles.

DECLARATIONS

Conflict of interest: none.

Funding: This work was supported by a grant from the Vice-chancellor for Research Affairs, Ahuaz Jondi – Shapour University.

Guarantor: RA.

Contributorship: RA has designed and supervised the project, NA has carried out the project and written the first draft of the manuscript and MTJ has been the laboratory methods consultant.

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Biochemical and nutritional indices as cardiovascular risk factors among Iranian firefighters

Abstract

Aim

Materials and methods

Results

Conclusions

Introduction

Methods

Subjects

Measurements

Statistics

Medical ethics

Results

Discussion

DECLARATIONS

References