Seasonal variation in hospitalisation for hypertension-related morbidities in Sokoto, north-western Nigeria.

OBJECTIVE: To determine the relationship between hospital admissions of hypertension-related morbidities, seasons and meteorological factors in a tropical climate. STUDY DESIGN: Retrospective analysis of hospitalised patients (440) with hypertension-related morbidities including heart failure (36.4 %), stroke (34.8%), chronic renal failure (7.1%) and others (21.7%) from 1995 to 2000. The relationship between hospital admission, seasons and meteorological factors was determined using simple proportions, univariate, multivariate and regression analysis. RESULTS: The subjects were aged 21-85 years and represented 9.3 % of all hypertensives and 7.0% of medical admissions. Mean blood pressure was 187.3 +/- 34.0/120 +/- 23 mmHg. Mild, moderate and severe hypertension occurred in 30 (6.8%), 59 (13.4%) and 351 (79.8%) patients, respectively. The monthly admission rate ranged from 3-11; (mean 6.1 +/- 1.9) patients. Admission rates peaked in January/February and August/September, corresponding with the peaks of harmattan and the wet seasons, respectively. Mean monthly admission rates were significantly higher during harmattan than during the hot season (6.7 +/- 2 versus 5.2 +/- 1.4 patients; p < 0.05), and during wet season than during the hot season (6.4 +/- 1.9 versus 5.2 +/- 1.4 patients; p < 0.05). Considering the hypertensives as a whole, a significantly higher proportion of patients was hospitalised during the cold season than during the hot season (11% versus 8.2%; odds ratio = 1.34). Linear regression analysis showed that hospital admission was significantly associated with the monthly minimum temperature (p = 0.02) and solar radiation (p = 0.01). Multiple regression analysis revealed that hospital admission was also significantly associated with combined meterological factors (temperature, radiation, dust haze days and relative humidity) (p = 0.04). CONCLUSIONS: Hospital admissions of patients with hypertension-related morbidities showed seasonal variation. Appropriate clothing and health planning during cold seasons are recommended.