Study on factors responsible for high life expectancy in the elderly population in the peripheral area of northwest Sinharaja forest

Sinharaja, a world heritage forest reserve, is one of the least disturbed and biologically unique lowland rain forests in Sri Lanka. Although a forest providing a conducive and healthy environment for high life expectancy is a general consensus, no such studies have been carried out. The main objective of the study was to find out the factors responsible for high life expectancy in the elderly population of northwest (NW) Sinharaja forest peripheral area. Two Grama Niladhari Divisions (GN) comprising six villages in the NW slope of Sinharaja forest were taken as the study area in the Kalawana District Secretariat Division. Of the total elderly population of 80 in the six villages, 61% of the elderly persons of both sexes of over 60 years were selected randomly for the study. A house to house approach based on a questionnaire survey was the primary investigation method. Interviews, case studies, and field observations were supplementary methods used. Simple statistical analysis such as percentages was used to interpret the data. The research was carried out between May-December 2011. Results show that the oldest in the sample was 99 years and in good health. Good quality food with indigenous knowledge on their food value, occupations directly linked to the forest which entailed long walks and fresh air, time for leisure, a simple life style without stress and tension has contributed to a higher life expectancy in the elderly population. Their memory was sharp and remembered over 100 food items gathered from the forest.


Introduction
Sinharaja forest reserve is one of the least disturbed and biologically unique lowland rain forests in Sri Lanka.This forest covers an extent of about 11187 hectares from east to west.The length of the forest is about 21 km and width from North to South is about 3.7km (Wijayawardena, 2010).It was declared a Man and Biosphere Reserve (MAB) in 1978, as a representative tropical humid evergreen forest eco system in Sri Lanka and has been recognized by UNESCO as part of its International Network of Biosphere Reserves.It was declared a world heritage site in 1989 and is situated in the southwest lowland of the wet zone of the country in the districts of Ratnapura, Galle and Matara.Ageing process in life is associated with progressive physiological, functional and pathological changes affecting their physical, mental, emotional and social well being.They manifest in changed physical and psychological performance, functional ability affecting daily living, mental and cognitive processing impacting on the productive aspect and on the quality of life.These occur in a milieu of cultural and religious values, changes in family and social structure (Senaratne, 2004).

Materials and Methods
Two Grama Niladhari Divisions (GN) comprising six villages in the NW slope of the Sinharaja forest was selected for the study.They are Kudawa, Pethiyakanda, Pitakele and Buthkanda villages of Kudawa GN division, and Suduwelipotha and Miyanapalawa villages of Weddagala North GN Division (Table 1and Figure 1).These GN divisions fall into the Kalawana District Secretarys Division in the Ratnapura District of the Sabaragamuwa Province.Of the total elderly populations of 80 persons in the six villages, 49 or 61.0% of the elderly persons of both sexes of over 60 years were selected randomly for the study.A house to house approach using a questionnaire was the primary investigation method adopted in the study.Interviews, case studies, and field observation were the other supplementary methods used.Simple statistical method such as percentages was used to interpret the data.The research was carried out between May -December in 2011.Table 1 shows the basic information regarding the elderly people in NW slope of Sinharaja forest.Table 3 shows different sources from where medicine had been obtained during an illness by the elderly people.As seen from the table, 49.9% of the medicine has been collected from the forest, 30.6 % from their garden and 16.3% from their own village indicating about 90.0% directly from their own surroundings.Venival, jatamansha, hatharavariya from the forest; pavatta, welpenela, rasakinda from their garden; vadhakaha and thora from the village were the common medicines mentioned by the elderly people.This indicates that the medicines used by them have been all natural products throughout their lives.

Conclusion
Good quality natural food and medicine with indigenous knowledge on the food and medicinal value, occupations directly linked to the forest which entailed long walks and exposure to unpolluted fresh air.A study on 680 persons between 51-97 years on lifetime exposure to polluted (air) environments by traffic pollution by Grey (2011) showed lower cognitive scores with poor memory.Another study by Power (2011) showed that the effect on the cognitive functions of people were equivalent to ageing by two years and with the doubling of carbon level it was 1.3 times more likely to have lower cognitive scores.In contrast, an unpolluted virgin forest provides a natural conducive environment for high life expectancy.A simple life style without stress and tension, engaging in religious activities, and keeping adequate leisure time has contributed to a higher life expectancy in the elderly population.Their good general health with razor sharp memory at this old age (remembering over 100 food items gathered from the forest) provides adequate testimony.According to Abeykoon (2004) a greater proportion of the rural women never reported illnesses which compares well with the elderly people of the Sinharaja peripheral community.

Table 1 .
Basic information of the elderly people in the NW slope of the Sinharaja forest periphery (Source: Field Survey, 2011) The oldest living person was 99 years.All the elderly persons in the sample had good health and sharp memory.Table 2 shows the former occupation of the elderly people of NW Sinharaja peripheral area.According to Table 2 the elderly population had been engaged in chena cultivation, collecting forest material, cutting kitul flowers and hunting.38.8% have been engaged in chena cultivation and 30.7% directly in collecting forest materials.All occupations show that they have been closely associated with the forest environment.

Table 2 .
Former occupation of elderly people of the NW Sinharaja forest periphery (Source: Field Survey, 2011)

Table 3 .
Sources of medicine consumed during an illness (Source: Field Survey, 2011)

Table 6 .
No. of elderly people who had/had not leisure times to spent after work.