Blood pressure variability and pedigree analysis of nocturnal SBP dipping in Kumbas from rural Chhattisgarh, India.

ABSTRACT

Family is the smallest unit of people to share most of the lifestyle, environmental and genetic factors. They are likely to have similarity in many physiological and behavioural aspects. Therefore, we designed a protocol to test the effect of large rural Indian families living together (Kumbas), on blood pressure variability. We also investigated the hypothesis that ‘nocturnal dipping’ in systolic blood pressure (SBP) is not heritable. Members of two families (1 and 2) consisting of 3-4 generations willingly participated in the study. Both families (natives of Chhattisgarh) belong to reasonably peaceful rural area and are financially stable. Farming is the main occupation of the members of both families. Few members of the families had jobs or small business. The null hypothesis regarding heritability of nocturnal dipping trait was accepted based on data emanating from either of the studied families. Hourly-averaged values depicted less variation in males and females of family 1 from midnight to early morning at around 0600, as compared to that in males and females of family 2. The 24 h averages of BP in family 2 were significantly higher as compared to that in family 1. Further, in family 2 the peaks of SBP, diastolic blood pressure (DBP) and mean arterial pressure (MAP) occurred significantly earlier as compared to that in family 1. The peak spread of SBP, DBP, heart rate (HR), MAP and pulse pressure (PP) among the members of family 1 was narrower than that for the members of family 2. Arbitrary cut-off values for classification of dipping, small sample size, and age dependency of nocturnal dipping might have marred outcome of the pedigree analysis of nocturnal dipping trait in this study. We have a hunch that the family shares typical temporal ups and downs in 24 h BP and HR. The above hypothesis needs confirmation based on studies with large data set involving subjective and objective assessment of the effects of psychosocial factors on BP and HR variability.