Background: The risk of obesity commonly changes with age, which is a longitudinal (aging) effect. Moreover, the individuals who enter the study at the same age have similar living conditions that may influence their obesity risk in a particular way; this is a cross-sectional effect. Both cross-sectional and longitudinal effects of age should be considered for a better understanding of the effect of age on obesity and the related factors.
Objectives: The present study aimed to (i) assess both the cross-sectional and longitudinal effects of age on obesity and (ii) determine how obesity changes with age in the target population using a Marginal Logistic Regression (MLR) model.
Methods: The current study made use of the information of individuals who had participated in the Isfahan Cohort Study. Participants were a large group of Iranian adults over 35 years of age who lived in the central region of Iran in 2001. Repeated measurements were obtained in 2001, 2007, and 2013.
Results: From 2001 to 2013, the percentage of obesity in men and women raised from 13% and 31% to 18% and 44%, respectively. Both cross-sectional and longitudinal effects of age were significantly associated with the odds ratio of obesity. There was a rise in the probability of obesity for individuals aged 35-60 years at baseline and a decline for the older ones. The odds of obesity had about a 2% increase (on average) per year, regardless of the baseline age.
Conclusion: The obtained results pointed to a difference between the cross-sectional and longitudinal effects of age on the probability of obesity in the target population. The high and rising prevalence of obesity was a serious public health issue among participants, especially women, aged 35-60 years. The assessment of changes in obesity in a population-based study provides opportunities to target subpopulations that need more care and attention in public health interventions.
- Emamian MH, Fateh M, Hosseinpoor AR, Alami A, Fotouhi A. Obesity and its socioeconomic determinants in Iran. Econ Hum Biol. 2017;26:144-50. doi: 10.1016/j.ehb.2017.03.005. [PubMed: 28395273].
- Seidell JC, Halberstadt J. The global burden of obesity and the challenges of prevention. Ann Nutr Metab. 2015;66(Suppl 2):7-12. doi: 10.1159/000375143. [PubMed: 26045323].
- Kilpi F, Webber L, Musaigner A, Aitsi-Selmi A, Marsh T, Rtveladze K, et al. Alarming predictions for obesity and non-communicable diseases in the Middle East. Public Health Nutr. 2014;17(5):1078-86. doi: 10.1017/S1368980013000840. [PubMed: 23642403].
- Rahmani A, Sayehmiri K, Asadollahi K, Sarokhani D, Islami F, Sarokhani M. Investigation of the prevalence of obesity in Iran: a systematic review and meta-analysis study. Acta Med Iran. 2015;53(10):596-607. [PubMed: 26615371].
- Azizi F, Azadbakht L, Mirmiran P. Trends in overweight, obesity and central fat accumulation among Tehranian adults between 1998–1999 and 2001–2002: Tehran lipid and glucose study. Ann Nutr Metab. 2005;49(1):3-8. doi: 10.1159/000084171. [PubMed: 15735362].
- Bahrami H, Sadatsafavi M, Pourshams A, Kamangar F, Nouraei M, Semnani S, et al. Obesity and hypertension in an Iranian cohort study; Iranian women experience higher rates of obesity and hypertension than American women. BMC Public Health. 2006;6(1):158. doi: 10.1186/1471-2458-6-158. [PubMed: 16784543].
- Bakhshi E, Etemad K, Seifi B, Mohammad K, Biglarian A, Koohpayehzadeh J. Changes in obesity odds ratio among Iranian adults, since 2000: Quadratic inference functions method. Comput Math Methods Med. 2016;2016:7101343. doi: 10.1155/2016/7101343. [PubMed: 27803729].
- Janghorbani M, Amini M, Willett WC, Gouya MM, Delavari A, Alikhani S, et al. First nationwide survey of prevalence of overweight, underweight, and abdominal obesity in Iranian adults. Obesity. 2007;15(11):2797-808. doi: 10.1038/oby.2007.332. [PubMed: 18070771].
- Khosravi-Boroujeni H, Sarrafzadegan N, Sadeghi M, Roohafza H, Talaei M, Ng SK, et al. Secular trend of metabolic syndrome and its components in a cohort of Iranian adults from 2001 to 2013. Metab Syndr Relat Disord. 2017;15(3):137-44. doi: 10.1089/met.2016.0073. [PubMed: 28135122].
- Sarrafzadegan N, Talaei M, Sadeghi M, Mohammadifard N, Lotfizadeh Dehkordi M, Esmaillzadeh A, et al. Determinants of weight change in a longitudinal study of Iranian adults: Isfahan cohort study. Arch Iran Med. 2014;17(8):539-44. [PubMed: 25065276].
- Djalalinia S, Saeedi Moghaddam S, Sheidaei A, Rezaei N, Naghibi Iravani SS, Modirian M, et al. Patterns of obesity and overweight in the iranian population: findings of STEPs 2016. Front Endocrinol. 2020;11:42. doi: 10.3389/fendo.2020.00042. [PubMed: 32174887].
- Djalalinia S, Peykari N, Qorbani M, Larijani B, Farzadfar F. Inequality of obesity and socioeconomic factors in Iran: a systematic review and meta-analyses. Med J Islam Repub Iran. 2015;29:241. [PubMed: 26793632].
- An R, Xiang X. Age–period–cohort analyses of obesity prevalence in US adults. Public Health. 2016;141:163-9. doi: 10.1016/j.puhe.2016.09.021. [PubMed: 27931993].
- Jaacks LM, Gordon-Larsen P, Mayer-Davis EJ, Adair LS, Popkin B. Age, period and cohort effects on adult body mass index and overweight from 1991 to 2009 in China: the China Health and Nutrition Survey. Int J Epidemiol. 2013;42(3):828-37. doi: 10.1093/ije/dyt052. [PubMed: 23771721].
- Keyes KM, Utz RL, Robinson W, Li G. What is a cohort effect? Comparison of three statistical methods for modeling cohort effects in obesity prevalence in the United States, 1971–2006. Soc Sci Med. 2010;70(7):1100-8. doi: 10.1016/j.socscimed.2009.12.018. [PubMed: 20122771].
- Mujahid MS, Diez Roux AV, Borrell LN, Nieto FJ. Cross‐sectional and longitudinal associations of BMI with socioeconomic characteristics. Obes Res. 2005;13(8):1412-21. doi: 10.1038/oby.2005.171. [PubMed: 16129724].
- Fitzmaurice GM, Laird NM, Ware JH. Applied longitudinal analysis. New Jersey: John Wiley & Sons; 2012.
- Diggle P, Diggle PJ, Heagerty P, Liang KY, Heagerty PJ, Zeger S. Analysis of longitudinal data. Oxford: Oxford University Press; 2002.
- Diouf I, Charles MA, Ducimetière P, Basdevant A, Eschwege E, Heude B. Evolution of obesity prevalence in France: an age-period-cohort analysis. Epidemiology. 2010;21(3):360-5. doi: 10.1097/EDE.0b013e3181d5bff5. [PubMed: 20375843].
- Sarrafzadegan N, Talaei M, Sadeghi M, Kelishadi R, Oveisgharan S, Mohammadifard N, et al. The Isfahan cohort study: rationale, methods and main findings. J Hum Hypertension. 2011;25(9):545. doi: 10.1038/jhh.2010.99. [PubMed: 21107436].
- Sarraf-Zadegan N, Sadri G, Malek-Afzali H, Baghaei M, Mohammadi-Fard N, Shahrokhi S, et al. Isfahan healthy heart programme: a comprehensive integrated community-based programme for cardiovascular disease prevention and control. Design, methods and initial experience. Acta Cardiol. 2003;58(4):309-20. doi: 10.2143/AC.58.4.2005288. [PubMed: 12948036].
- Sarrafzadegan N, Baghaei A, Sadri G, Kelishadi R, Malekafzali H, Boshtam M, et al. Isfahan healthy heart program: evaluation of comprehensive, community-based interventions for non-communicable disease prevention. Prev Control. 2006;2(2):73-84. doi: 10.1016/j.precon.2006.10.003.
- Sarrafzadegan N, Hassannejad R, Roohafza H, Sadeghi M, Talaei M, Oveisgharan S, et al. A 10-year Isfahan cohort on cardiovascular disease as a master plan for a multi-generation non-communicable disease longitudinal study: methodology and challenges. J Hum Hypertens. 2019;33(11):807-16. doi: 10.1038/s41371-018-0126-2. [PubMed: 30385824].
- Sadeghi M, Talaei M, Gharipour M, Oveisgharan S, Nezafati P, Dianatkhah M, et al. Anthropometric indices predicting incident hypertension in an Iranian population: the Isfahan cohort study. Anatol J Cardiol. 2019;22(1):33-43. doi: 10.14744/AnatolJCardiol.2019.10594. [PubMed: 31264654].
- World Health Organization. Noncommunicable diseases country profiles. Geneva: World Health Organization; 2018.
- Fitzmaurice G, Davidian M, Verbeke G, Molenberghs G. Longitudinal data analysis. Florid: CRC Press; 2008.
- Blüher[S1] M. Obesity: global epidemiology and pathogenesis. Nat Rev Endocrinol. 2019;15(5):288-98. doi: 10.1038/s41574-019-0176-8. [PubMed: 30814686].
- Asgari F, Biglarian A, Seifi B, Bakhshi A, Miri HH, Bakhshi E. Using quadratic inference functions to determine the factors associated with obesity: findings from the STEPS Survey in Iran. Ann Epidemiol. 2013;23(9):534-8. doi: 10.1016/j.annepidem.2013.07.006. [PubMed: 23958406].
- Bakhshi E, Seifi B, Biglarian A, Mohammad K. Factors associated with obesity in Iranian elderly people: results from the national health survey. BMC Res Notes. 2011;4(1):538. doi: 10.1186/1756-0500-4-538. [PubMed: 22168800].
- Hickson M. Malnutrition and ageing. Postgrad Med J. 2006;82(963):2-8. doi: 10.1136/pgmj.2005.037564. [PubMed: 16397072].
- Blüher M. Obesity: global epidemiology and pathogenesis. Nat Rev Endocrinol. 2019;15(5):288-98. doi: 10.1038/s41574-019-0176-8. [PubMed: 30814686].
- Rashidy‐Pour A, Malek M, Eskandarian R, Ghorbani R. Obesity in the Iranian population. Obes Rev. 2009;10(1):2-6. doi: 10.1111/j.1467-789X.2008.00536.x. [PubMed: 19021868].
- Azizi F, Allahverdian S, Mirmiran P, Rahmani M, Mohammadi F. Dietary factors and body mass index in a group of Iranian adolescents: Tehran lipid and glucose study-2. Int J Vitam Nutr Res. 2001;71(2):123-7. doi: 10.1024/0300-9822.214.171.124. [PubMed: 11339109].
- Kelishadi R, Alikhani S, Delavari A, Alaedini F, Safaie A, Hojatzadeh E. Obesity and associated lifestyle behaviours in Iran: findings from the first national non-communicable disease risk factor surveillance survey. Public Health Nutr. 2008;11(3):246-51. doi: 10.1017/S1368980007000262. [PubMed: 17625028].
- Hajian-Tilaki K, Heidari B. Association of educational level with risk of obesity and abdominal obesity in Iranian adults. J Public Health. 2010;32(2):202-9. doi: 10.1093/pubmed/fdp083. [PubMed: 19689983].
- Sassi F, Devaux M, Church J, Cecchini M, Borgonovi F. Education and obesity in four OECD countries. New York: OECD Publishing; 2009.
- Kim YJ. The long-run effect of education on obesity in the US. Econ Hum Biol. 2016;21:100-9. doi: 10.1016/j.ehb.2015.12.003. [PubMed: 26828291].