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 "Time to switch to 'Rule of three-Quarters' from 'Rule of Halves' in hypertension ?

By: Ritika Sharma 

Date : August 19th,2022 

Author : Imaad Mohammed Ismail, Subhashree Nandy, Shubhankar Adhikari, Revathi TM,Dhruv Gupta, Deeptha M, Awnish Ranjan, Aslaha Aboobacker .

In India, the National Family Health Survey-4 (NFHS-4) data states that 11% of women and 15% men in the age group 15-49 years have hypertension. This was a cross-sectional study carried out in Madani Nagar, Dakshina Kannada from February to April 2020. 

The study was taken up by authors to understand if the traditional ‘rule of halves’ of hypertension still prevails or is it time to shift to the proposed ‘rule of three-quarters’, The Dakshina Kannada district of Karnataka is a well-performing district with higher than national average literacy rate and health care facilities.they  wanted to assess whether in a population like Madani Nagar, which is located in a better performing district of India, the concept of ‘rule of halves’ has shifted towards ‘rule of three-quarters’.The objectives of the study were to estimate :

(i) the prevalence of hypertension among adult residents of Madani Nagar rural community in the Dakshina Kannada district of Karnataka state in southern India,

 (ii) the proportion who are aware of their disease among hypertensive patients,

 (iii) the proportion who are on treatment among those who are aware of their disease, and

 (iv) the proportion having adequate blood pressure control among those on treatment.

 661 individuals were enrolled in the study , majority of the individuals (43.1%) enrolled were in the age group of 25-44 years. An increasing trend of prevalence of hypertension was observed from age 18-79 years, the prevalence of hypertension was 29.2% , only 55.4% of hypertensive patients were aware that they had the disease, and among them, 96.3% were on treatment. Among those on treatment , 58.3% had adequate control of blood pressure

Report on Rule of Hypertension

Figure 1: Originally depicted rule of halves of hypertension (A) and depiction of rule of halves in the study population (B

Hypertension is a disease that exhibits an iceberg phenomenon due to its asymptomatic nature and the mere existence of the ‘rule of halves’ reflects poorly on the awareness regarding the disease. The ‘rule of halves’ has three component :-

The first component talks about the proportion of hypertensive individuals that are aware of their disease status. In the present study, 107 out of 193 (55.4%) hypertensive individuals were aware that they had hypertension. The result leans towards the ‘rule of halves’ rather than the proposed ‘rule of three-quarters’, and it suggests that the secondary level of prevention (i.e., early diagnosis and treatment) has failed for about half the hypertensive individuals.

 A study done by Kantha et al. in a rural setting showed a similar result where 58.5% of hypertensive individuals were aware about their status of hypertension . On the contrary, a study done by Hadaye et al. in the urban parts of Mumbai found that 74.4% of hypertensive individuals knew that they had hypertension .

The second component of the ‘rule of halves’ focuses on the proportion of hypertensive individuals on treatment from among those who are aware of their disease. A striking result of 96.3% of hypertensive individuals on treatment inclined more towards the ‘rule of three-quarters’ proposed in this study than the traditional ‘rule of halves’.

The third component of the ‘rule of halves’ depicts the proportion of hypertensive persons who are on treatment that have adequate control over their blood pressure levels. As per the results of the current study, about 60% of the people taking treatment had adequate control and this leans more towards the ‘rule of halves’ than the proposed ‘rule of three-quarters’. It is also important to note that if we consider all the hypertensive individuals irrespective of whether they are on treatment or not, then a meagre 60 out of 193 (31.1%) have actually achieved adequate blood pressure control. 

Data was collected by trained second-year undergraduate medical students under the supervision of the principal investigator using a semi-structured questionnaire through the Epicollect 5 application .
To measure the blood pressure, they used a digital automatic blood pressure monitor (model Omron HEM-7130-L), which has an accuracy of +/- 3mm Hg . World Health Organization's guide to physical measurements was followed for patient preparation and blood pressure recording . After fifteen minutes of rest, two blood pressure readings were taken 10 minutes apart and the average reading was considered for classifying as ‘hypertension’ or ‘without hypertension’. Data was analyzed using Microsoft excel. 

The overall findings reveal that the study population parameters such as ‘the proportion of the hypertensive individuals who are aware that they have the disease’ and ‘the proportion of people taking treatment who have adequate blood pressure control’ leans more towards the traditional ‘rule of halves’. However, the study population parameter of ‘the proportion of hypertensive people who are aware of their disease that are taking treatment’ leans more towards the proposed ‘rule of three-quarters’. 

The authors of the study wanted to know if factors related to diagnosis and treatment of hypertension have sufficiently improved and if it is time to shift and adopt the proposed ‘rule of three-quarters’. The findings of the study suggest that at present the ‘rule of halves’ continues to be a better fit as compared to the ‘rule of three-quarters’.