Risk Factor for Health Care Workers Developing Hypertension: A Nested Case-Control Study

Abstract

Background and Objectives: 

The study was aimed to evaluate the role of stress, lifestyle as well as traditional risk factors in the development of hypertension among health-care workers (HCWs).

Methods: 

This nested case–control study was done at a tertiary care university teaching hospital in South India. Cases were hospital employees diagnosed with hypertension and who were taking antihypertensive medications. Controls were age- and sex-matched HCWs who were not diagnosed with hypertension. They were identified preferably in the same department where its case was presently working. One hundred and twenty-eight cases and 128 controls were enrolled. We collected data on risk factors for hypertension, physical activity, diet, and stress. Those significant on the bivariate analysis were entered into a logistic regression analysis.

Results and Interpretation: 

In the logistic regression, we found that living in a joint family (2 siblings and their families), family history of hypertension, family history of diabetes mellitus, and family history of ischemic heart disease were independently predictive of hypertension developing in the study HCWs. Occasional or regular walking/cycling to work and milk consumption were independent factors that protected against the development of hypertension. Extra added salt to food and stress more than normal in any domain tested were not associated with the development of hypertension in our cohort.

Conclusions: 

HCWs have some novel and other similar risk factors to general population for developing hypertension. Simple preventive measures seem effective. Neither stress nor self-reported salt consumption seemed to play a role in the development of hypertension.

Introduction

Hypertension contributes to 9.4 million deaths annually worldwide.^[1] The World Health Organization (2012) estimated that the prevalence of hypertension in India was 23.1% and 22.6% among adult men and women, respectively.^[2] Hypertension is prevalent in nearly a third of health-care workers (HCWs).^[3,4] Among nurses in South Africa, 41% were unaware of having hypertension^[5] while masked hypertension has been documented in 25% of HCWs in Spain.^[6]

The Nurses’ Health Study^[7] and the Physicians’ Health Study^[8] have studied lifestyle and diet on development of hypertension in the United States We aimed to evaluate the role of stress, lifestyle as well as traditional risk factors in the development of hypertension among HCWs.

Materials and Methods

This nested case–control study was done at the Christian Medical College (CMC), Vellore, a tertiary care university teaching hospital in South India. It has 8000 employees, including doctors, nurses, allied health professional, and administrative and support staff. Medical checkups are done for all employees at joining. They thus form a cohort in whom we have done this nested case–control study After joining, all employees are offered voluntary regular preventive health checkups by the Department of Staff Students Health Services. Over the years, some have been diagnosed with hypertension while others have not. Health data are available in electronic medical record form. The Institutional Review Board and Ethics Committee approval was obtained prior to enrollment of participants (IRB Min No. 8249 dated March 19, 2013). Data were collected prospectively regarding cases and controls from July 2013 to July 2014 regarding health related issues from the time of employment till the interview date [Annexure 2]. We excluded those who had discontinued antihypertensive medications, currently pregnant, and those who refused consent.

Annexure 1: Strobe figure

Annexure 2: PRO FORMA

Cases

Cases were hospital employees working in CMC, diagnosed with hypertension, and who were taking antihypertensive medications. Controls: for every case, age- and sex-matched control was identified in the ratio 1:1. They were hospital employees who were not diagnosed with hypertension and were not taking any antihypertensive medications. Each of them was identified preferably in the same department where its case was presently working and was within 5 years above and below the age of the identified case.

Sample size

We estimated odds ratio of 3 for stress among cases with a probability of 20% stress among controls; with 80% power, 5% alpha error, and equal number of cases and controls, sample size was 128 cases and 128 controls.

Method of evaluation

We screened 625 employees’ records randomly for eligibility as cases or controls. Among those who were on antihypertensive medications, we provided information sheets about the study. Those who gave informed consent were recruited [Annexure 1]. Among the employees who did not have hypertension, a random sample of 128 participants were chosen based on the control definition given above. We administered a study-specific clinical research form for data collection [Annexure 1]. Broadly, we collected data on demography, known risk factors for hypertension, physical activity, diet, and stress. Level of physical activity was assessed according to the Global Physical Activity Questionnaire.^[9] The questions about diet pattern were based on the Dietary Approaches to Stop Hypertension (DASH) approach.^[10] As previous tools for stress were not specific for all classes of HCWs, we developed an instrument based on expert opinion. Senior faculty of the department reviewed the instrument for content and face validity. This tool assessed stress at the family, relationships, and financial and work-related levels. We asked the following six questions. Did you feel that you had to face chronic difficulty outside of work (family, relationship, and financial)? Do you remember having increased work problems (excessive working hours, fluctuating shifts and workloads, and coping with new situations or new technology? Were you having feelings of job insecurity? Did you feel that you lacked a confidant/co-worker support/supervisor support? Were you facing a substantial health difficulty in a close relative? Were you going through a difficult time in your marriage? The response for each question was categorized as stress level same as usual, stress less than usual, stress more than usual, and no stress not at all. All responses on stress related issues were taken if they were in months preceding the diagnosis of hypertension. We considered stress to be significant when the response to any of the questions was stress “more than usual.” We hypothesized that if a participant was stressed in one area of life around the time of diagnosis of hypertension, he/she may have faced stress in other areas, but while answering the questionnaire will only remember the major stressful event and not the all the stressors present around the time of diagnosis.

Statistical analysis

EpiData 3.1 software was used for data entry. Data were analyzed using IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY, USA: IBM Corp. For continuous variable with normal distribution, independent “t” test of significance was used, otherwise Mann–Whitney U-test was used. For categorical variables, Chi-square test was used. Those significant on the univariate analysis were entered into a logistic regression analysis. Goodness of fit was assessed using the Hosmer and Lemeshow test and the model summary using the Nagelkerke R square.

Results

The crude incidence of hypertension among the cohort was 20.48% (128/625). The mean age of cases and controls was 44.6 (7.8) and 43 years (7.2) (mean [standard deviation (SD)]), respectively [Annexure 3]. Most of the participants (98.5% and 96.1%) were married. Although we matched, there were more women 72 (56.3%) among cases than controls 63 (49.2%). There were 52 (40.6%) and 50 (39.1%) nurses in cases and controls, respectively. Doctors were 52 (40.6%) and 32 (25%), respectively, while technical and nonmedical employees 18 (14.1%) and 25 (19.5%). The mean number of years to develop hypertension among cases was 8.45 ± 3.8 years (mean [SD]). The mean blood pressure at the time of employment was 111.7 (7.8) and 114.9 (7.5) systolic and 72.9 (6.9) and 71.2 (9.2) mmHg diastolic among cases and controls, respectively. The univariate comparison of cases and controls [Table 1] shows that overall 12.5% of participants had “more than normal” stress levels in any one or more domains tested (15.6% and 9.4% among cases and controls, respectively).

Annexure 3: Baseline characteristics

Table 1: Distribution of participants as per multivariate logistic regression of dependent variable on some of their attributes (n=128)

In the logistic regression, we found that living in a joint family (2 siblings and their families), family history of hypertension, family history of diabetes mellitus, and family history of ischemic heart disease were independently predictive of hypertension developing in the study HCWs. Obesity and obstructive sleep apnea were not associated with the development of hypertension. Occasional or regular walking/cycling to work and milk consumption were independent factors that protected against the development of hypertension. Neither extra added salt to food or stress more than normal in any domain tested were associated with the development of hypertension in our cohort. The model goodness of fit was good (P = 0.165) and the Nagelkerke R² 0.675. The model including gender did not change the analysis (not shown).

Discussion

Our nested case–control study of hypertension and risk factors among a large cohort of HCWs found 20% hypertension. This is similar to a study from Delhi;^[11] however, other studies have reported a 30% or higher incidence.^[3,4] The risk factors that we identified as independently predicting the development of hypertension were previously well described, family history of hypertension, diabetes, and ischemic heart disease.

Living in a joint family was also independently associated with hypertension, OR 5.33 (95% CI 1.61 17.7), a novel finding. This could possibly be due to increase stress as part of a joint family. An earlier study by Thadathil et al. found that social relationships were better in nuclear families.^[12] A Japanese study found more severe hypertension in those living alone or nuclear families as compared to joint families.^[13] In our geographic and social context, joint families seem to increase the chance of hypertension. The mechanism may be complex.

However, stress as measured by our instrument did not predict development of hypertension, adjusted odds of 2.18 (0.89–5.38). A Nigerian study of HCWs reported 26.2% with work-related stress; among them, 42% had hypertension.^[14] In Nepal, perceived stress as measured by the Cohen’s Perceived Stress Scale-10 was an independent risk factor for hypertension among HCWs.^[3] Administrative employees of the All India Institute of Medical Sciences in Delhi had a 20.7% prevalence of hypertension. Stress as measured by the Holmes and Rahe Stress Inventory Scale–Social Readjustment Rating Scale was seen in 12.7%.^[15] Some other scales used include the Expanded Nursing Stress Scale which addresses different aspects of stress in nursing life using a 57-item questionnaire within the past 1 year.^[16] However, our study population consists of HCWs across all classes of workers.

Interestingly, we found that participants who walked or cycled less to work were at risk. Nurses with a history of gestational hypertension who adhered to lifestyle changes were shown to have less incident hypertension.^[7]

A study of 30,681, health care professionals in the US, increased calcium intake was associated with lower blood pressure in lean men.^[8] We identified lower milk consumption (possibly lower dietary calcium) as a risk factor. Fiber and fruit consumption has also been described to be protective for hypertension in the health professional’s study. We did not find that added salt in addition to the salt in the cooked food was a risk factor. We did not measure fiber intake in food. Some well-described risk factors such as obesity, obstructive sleep apnea, and smoking were not found to be associated with incident hypertension in our study.

Limitations

While we attempted to look at stress around the time of diagnosis of hypertension, this is subject to recall bias. We did not do a formal food frequency questionnaire of 24-h food recall. As the number of employees in some categories was small, we could not use these variables in the logistic regression analysis.

Conclusion

Living in a joint family, family history of hypertension, and family history of diabetes mellitus were risk factors for developing hypertension while occasional or regular walking or cycling to work and milk intake were independent protective factors for development of hypertension in HCWs in our institute. Many of these are modifiable and studies that modify them and look at reduction in incidence of hypertension among HCWs are required.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.