Seasonal variation in prevalence of hypertension: Implications for interpretation.

Objectives: To study seasonal variation in prevalence of hypertension. Materials and Methods: The study was carried out in the year 2006, in Gokulpuri, an urban slum located in eastern part of Delhi. 275 females 18-40 years of age were examined in summer. Blood pressure was measured in two seasons, summer and winter. Nutritional status of each individual was assessed by BMI. Results: The prevalence of hypertension based on SBP was 12.72% in summer which increased to 22.22% in winter. The prevalence of hypertension, using DBP criteria increased to more than double (summer vs. winter, 11.27% vs. 26.59%, P< 0.001). Overall prevalence of hypertension (SBP≥140 or DBP≥90 mm of Hg) was 1.9 times during winter compared to summer (P<0.001). Greater increase in prevalence of hypertension during winter among older females and underweight as well as normal females was observed. Conclusion: Significant increase in prevalence of hypertension during winter compared to summer indicates need for considering this factor while comparing prevalence reported in different studies as well as interpreting the surveillance data based on repeat surveys.