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== Seasonal changes in blood profile == A Study Conducted at Nishtar Medical College, Multan, Pakistan Authors: Mohammad Nauman Malik Hamid Javed Qureshi Tahseen Iqbal Asghar Javed

ABSTRACT

The blood pictures of healthy medical students were studied in the last week of June, 2003 and the last week of January, 2004 to find the seasonal variations. Total leukocyte, absolute neutrophil, absolute lymphocyte and red blood cell counts and hemoglobin concentration were highly significantly (P< 0.001) higher in the summer than in the winter. Packed cell volume was also significantly (P<0.01) higher in the summer. Mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC) and platelet count showed a non-significant (P<0.05) difference between the two seasons. It is concluded that there are significant seasonal variations in the blood picture of healthy young adults.

INTRODUCTION

Pakistan lies in the temperate zone of the world. The climate in south Punjab is characterized by very hot summers and cold winters. The temperature rises above 45o C during the summer and falls to about 2 – 3o C in the winter. Temperature during the summer is high because the sun directly shines over the earth’s surface. There are seasonal changes not only in the temperature but also in atmospheric pressure, thickness of atmosphere and the length of the day time1. These changes may affect the blood picture. Seasonal variations in blood picture depend upon the physiological adaptations of the body to the new sets of environmental conditions2. Meteorologically conditioned fluctuations in the blood picture have been reported3. Heat and solar radiation have been reported to cause leukocytosis4, 5. There is also circadian rhythm of blood eosinophil count which is mediated by suprachiasmatic nuclei of hypothalamus via retino-hypothalamic fibers6. An increase in the erythrocyte count in chronic exposure to low atmospheric pressure has also been reported7. this study was conducted to find out variations in the blood picture in the summer and the winter.

SUBJECT AND MATHODS

Sixty three healthy medical student were included in the study. Their age ranged between 19 – 21 years. Students having fever, any infection or history of season associated allergy or drug intake were not included in the study. Two blood samples were taken from each subject in the morning (9:00 – 10:00 am). First sample was taken in the last week of june, 2003 and the second was taken in the last week of june, 2004. these blood samples were analyzed for the blood picture by the Hematology Blood Cell Counter – SYSMEX – KX – 21). Modern blood counting systems provide a high level of precision, so that even small differences in successive measurements may be significant8.

RESULTS:

The temperature and atmospheric pressure data during the study period obtained from Pakistan Metereological Department, Multan is shown in Table 1.

[[Image:Table 1: Temperature and Atmospheric Pressure Data.

Atmospheric   Summer (June 2003)       Winter (January 2004) Parameters 1)Temperature (°C) 	            39 – 49	             6 – 10 2)Pressure (Hecta Pascal)   994 – 997	             1013 – 1018]]

[[Image:Table 2: Variation in Leukocyte and Platelet Counts in Summer and Winter.

No. Blood	Summer	      Winter	     T Value	   P Value parameters

1  TLC         7.3±0.17       6.6 ± 0.1     15.64	   <0.001**

2  N    	4.4 ± 0.15     3.38 ± 0.13   14.60	   <0.001**

3  L    	2.4 ± 0.08     2.1 ± 0.07    22.70	   <0.001**

4  P	        2.50 ± 7.05    2.49 ± 6.47   0.11	   >0.05*


 * Highly significant
 * Non-significant

TLC: Total Leukocyte Count (10000/ul) N: Absolute Neutrophil Count " L: Absolute Lymphocyte Count " P: Total Platelet Count     "]]

[[Image:Table 3: Variation in RBC Count, Hemoglobin and Red Cell Indices in Summer and Winter.

No.	Blood 	     Summer	    Winter        T Value   P Value Parameters

1	RBCs	     4.9 ± 0.02    4.7 ± 0.07	  17.60	   <0.001***

2	HB (g/dl)    13.3 ± 0.2    12.7 ± 0.2	  5.50	   <0.001***

3	PCV (%)	     41.2 ± 0.53   39.6 ± 0.61	  2.50	   <0.01**

4	MCV(fL)	     84.43 ± 0.89  84.45 ± 0.82  -0.02	   >0.05*

5	MCHb pg/dL)  27.19 ± 0.40  27.13 ± 0.11  0.12	   >0.05*

6	MCHC (g/dL)  32.11 ± 0.18  32.04 ± 0.17  1.82	   >0.05*

RBCs: Total Red Blood Cell Count (10000000/ul) HB: Hemoglobin Concentration PCV: Packed Cell Volume MCV: Mean Cell Volume MCHb: Mean Cell Hemoglobin MCHC: Mean Cell Hemoconcentration
 * Highly Significant	* Non-significant
 * Significant]]

There was highly significant (P<0.001) rise in total leukocyte, absolute neutrophil and absolute lymphocyte counts in the summer as compared to the winter. The platelet count showed a non-significant (P>0.05) increase in the summer (Table 2). Red blood cell count and hemoglobin concentration were highly significantly (P<0.001) higher in the summer than in the winter, while packed cell volume (PCV) was higher significantly (P<0.01) in the summer (Table 3). Mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) showed a non-significant (P>0.05) difference between the two seasons (Table 3).

DISCUSSION

The present study revealed seasonal variations in the blood picture in young healthy adults. Total leukocyte, absolute neutrophil, absolute lymphocyte and red blood cell counts and hemoglobin concentration were highly significantly higher in summer than in winter. The MCV, MCH, MCHC and platelet count showed statistically non-significant difference in the two seasons. Muchmore (1970)10 reported that prolonged residence in Antarctica caused leucopenia. The increase in leukocyte counts in the summer is due to the effect of increased temperature, sun light and ultraviolet rays4, 5. The rise in the erythrocyte count, hemoglobin concentration and packed cell volume during summer is due to lower atmospheric pressure7. It is concluded that there are significant seasonal variations in the blood picture of young healthy adults.