Our study showed a prevalence of 34% DD in non-diabetic patients of MS. This is significantly lower than the prevalence seen in other studies from the Indian subcontinent (1,3,4). All of these studies were done in diabetic MS patients. A study by Dinh et al in 2011 was done on 166 patients, dividing them into 3 groups; Impaired Glucose Tolerance (IGT), Diabetic and Non Diabetic group (NGT). The prevalence of DD was 81% in the IGT group, 96% in the diabetic group and 61% in the NGT group, respectively (P< 0.001). Twelve percent of subjects with NGT, 28% of patients with IGT and 35% of the diabetic group were classified as having a more severe form of LVDD (14).
Given the high prevalence of DD in diabetic patients, with some studies showing a prevalence up to 100% (15), it would be tempting to conclude that Diabetes is the predominant contributor to DD in MS.
The review of literature places the prevalence of DD in hypertensive patients in a variable range. While in the Caucasian population, the incidence appears to be in the range of 40-45% (16), the prevalence in South East Asian and African populations are higher. Independent small sample size studies from India report the prevalence of DD in hypertensives to be between 55-70% (17,18) while a Nigerian population study placed the incidence of DD in hypertensive patients at 82% (19). The E-ECHOES study done in the United Kingdom on hypertensive patients of South East Asian ethnicity put the prevalence at 73%,which was comparable to that seen in the African-Caribbean population (72%).However, the parameters of DD were worse in the South East Asian group translating to worse clinical outcomes.(20)
In our study 42 patients had past history of hypertension, 57% of whom had DD. 43 were newly diagnosed,20 % of whom had DD. Long standing history of hypertension was significantly associated with DD in our study.27 patients had history of dyslipemia,22 of whom had DD(84%). Out of the 73 newly diagnosed patients,12 had DD(17%).Thus while no significant association between dyslipidemia and hypertension with DD in our study, a very strong association is present between past h/o hypertension and dyslipidemia.
The lack of significant association between individual variables of MS and DD is a feature unique to our study;almost all other studies have shown significant association between each component with DD { exception being some studies which showed no association with low HDL levels ( 8) }. However, after carefully reviewing all literature,we were unable to find whether the patients who were selected in various studies, had long standing history of the 3 central disorders which comprise MS or whether the elevations were stand alone values. We propose that it is not isolated elevations of the components, but long standing disease which is responsible for causing the cardiac effects.
There are conflicting reports regarding gender distribution of DD in MS( 21). Our study did not reveal any gender inequality which is similar to several other studies( 17,18)
MS is a complex constellation of various diseases which is greater than the sum of its whole. How the components interact with each other and whether one component is more important than others, is a question which has not been answered yet. It would require studies both long term and well defined before we come close to the answer. While the significantly lower prevalence of DD in our study after excluding diabetics, certainly appears to suggest that diabetes is a major contributor to DD in MS, more such studies are required before we can reach a conclusion.
Limitations:
One of the major limitations of our study is the comparatively younger group of patients studied. The average age of our patients was 43years. Since age has a well known association with DD in MS (17,18) it is a possibility that the lower prevalence of DD in our study could be explained by this.